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Effects of Head Posture on Cerebral Hemodynamics: Its Influences on Intracranial Pressure, Cerebral Perfusion Pressure, and Cerebral Oxygenation
Abstract
Severely head-injured patients have traditionally been maintained in the head-up position to ameliorate the effects of increased intracranial pressure (ICP). However, it has been reported that the supine position may improve cerebral perfusion pressure (CPP) and outcome. We sought to determine the impact of supine and 30 degrees semirecumbent postures on cerebrovascular dynamics and global as well as regional cerebral oxygenation within 24 hours of trauma.
Patients with a closed head injury and a Glasgow Coma Scale score of 8 or less were included in the study. On admission to the neurocritical care unit, a standardized protocol aimed at minimizing secondary insults was instituted, and the influences of head posture were evaluated after all acute necessary interventions had been performed. ICP, CPP, mean arterial pressure, global cerebral oxygenation, and regional cerebral oxygenation were noted at 0 and 30 degrees of head elevation.
We studied 38 patients with severe closed head injury. The median Glasgow Coma Scale score was 7.0, and the mean age was 34.05 +/- 16.02 years. ICP was significantly lower at 30 degrees than at 0 degrees of head elevation (P = 0.0005). Mean arterial pressure remained relatively unchanged. CPP was slightly but not significantly higher at 30 degrees than at 0 degrees (P = 0.412). However, global venous cerebral oxygenation and regional cerebral oxygenation were not affected significantly by head elevation. All global venous cerebral oxygenation values were above the critical threshold for ischemia at 0 and 30 degrees.
Routine nursing of patients with severe head injury at 30 degrees of head elevation within 24 hours after trauma leads to a consistent reduction of ICP (statistically significant) and an improvement in CPP (although not statistically significant) without concomitant deleterious changes in cerebral oxygenation.
... However, limited data exist about the effects of head posture on concomitant cerebral blood flow, brain oxygenation, ICP, and CPP measurements after acute brain injury. In patients with traumatic brain injury (TBI), elevating the head from 0° (supine position) to 30° significantly decreased ICP and was associated with no change in brain oxygenation, as indicated by jugular bulb venous oxygen saturation and/or brain tissue oxygenation pressure (PbtO 2 ) [3,6,14]. In patients with large hemispheric stroke, a change in head elevation from 0° to 30° was associated with a reduction in both ICP and mean blood flow velocity (FVm) of the affected hemisphere [15]. ...
... This latter point was recently addressed in a trial that revealed no difference in the neurological outcomes after acute stroke between patients positioned in a flat posture and those positioned in a 30° upright posture [23]. In addition, the complex interplay between ICP, brain oxygenation, and circulation, as well as the timing of measurements, required appropriate statistics (i.e., linear random-slope mixed models), which were not used in previous studies [3,6,14,15]. ...
... In the study by Ng et al. [14], which found that PbtO 2 values did not differ significantly by head elevation, PbtO 2 measurements ranged from 6 to 100 mm Hg at a 0° head elevation and from 4 to 92 mm Hg at a 30° head elevation, making it difficult to draw any conclusions about the true effects of head positioning. In the present study, FVm was higher in a flat position than at a 30° head elevation, as observed previously [15]. ...
Background
Therapeutic head positioning plays a role in the management of patients with acute brain injury. Although intracranial pressure (ICP) is typically lower in an upright posture than in a flat position, limited data exist concerning the effect of upright positioning on brain oxygenation and circulation. We sought to determine the impact of supine (0°) and semirecumbent (15° and 30°) postures on ICP, brain oxygenation, and brain circulation.Methods
An observational cohort study was conducted between February 2012 and September 2015. Twenty-three patients with severe acute brain injury were successively observed at head elevations of 30°, 15°, and 0°. Postural-induced changes in ICP, cerebral perfusion pressure, brain tissue oxygenation pressure, and transcranial Doppler findings were simultaneously measured during three repeated experiments: 24 h after admission to the intensive care unit (exp1), 24 h later (exp2), and 96 h later (exp3). Cerebral perfusion pressure, arterial blood gases, hemoglobin content, and body temperature remained unchanged during the three experiments.ResultsUsing linear random-slope mixed models, we found that during the early phase of acute brain injury (exp1), lowering the head posture from 30° to 15°, and then to 0°, was associated with a gradual mean ICP increase of 2.6 mm Hg (1.4–3.7 mm Hg; P < 0.001); and from 30° to 0°, an increase of 7.4 mm Hg (6.3–8.6 mm Hg; P < 0.001). Furthermore, brain tissue oxygenation pressure and mean blood flow velocity improved when the head posture was lowered from 30° to 0° by 1.2 mm Hg (0.2–2.3 mm Hg) and 4.1 cm/s (0.0–8.2 cm/s), respectively (both P < 0.05).Conclusions
Changing the positioning of stable patients with acute brain injury resulted in opposite changes of ICP versus brain oxygenation and circulation. This information supports the concept of an individualized approach to head positioning that is based on the multimodal monitoring of brain parameters.
... Ultrasonographic optic nerve sheath diameter (USG-ONSD) measurement is a practical, inexpensive, convenient, and reliable type of indirect ICP measuring modality that helps in assessing ICP non-invasively [5,6]. Many research works have investigated the effect of Trendelenburg, reverse Trendelenburg, and prone positioning on USG-ONSD [7][8][9][10]. ...
... Ample literature has been found on the effects of different postures on ONSD and ICP [2,[6][7][8][9]. However, the effect of head rotation in any posture has not been commented on in any of the studies. ...
Background
Extreme neck positioning to facilitate craniotomy can result in impaired venous drainage from the brain and a subsequent rise in increased intracranial pressure (ICP). The effects of varied neck positioning intraoperatively on ultrasonographic optic nerve sheath diameter (USG-ONSD) are still unexplored. This study aims to quantify the angle of neck rotation and flexion that can cause a significant increase in USG-ONSD in patients undergoing elective craniotomy.
Methods
A total of 100 patients were recruited in this non-randomized study and equally divided into two groups. In one group, patients with neck rotation ≤30 degrees and in another group, patients with neck rotation >30 degrees with varying degrees of neck flexion were included. The average of three USG-ONSD measurements in both eyes was obtained and compared in both groups at baseline, after positioning, and at the end of the surgery after making the neck neutral.
Results
The results of 100 recruited patients were analyzed. All the patients had neck flexion in the range of 40° to 45°, whereas the neck rotation ranged from 10° to 45°. The USG-ONSD of both eyes changed significantly from baseline to post-positioning time point in patients with neck rotation >30° (right eye p=0.038, left eye p=0.04) when compared to neck rotation ≤30°. There was no significant change in USG-ONSD from baseline to the postoperative time point after making the neck neutral (right eye p=0.245, left eye p=0.850) in both groups.
Conclusions
This study demonstrates that USG-ONSD, a surrogate measure of ICP, increased significantly after neck flexion with rotation >30° in neurosurgical patients. However, USG-ONSD becomes comparable to baseline after putting the patient's neck in a neutral position after surgery.
... Dynamic situations in neurosurgical patients, such as surgery for brain tumors, cerebrovascular disorders, and postoperatively nursed head and body positions, may alter CBF and CPP [12]. Results of previous studies regarding the association of CBF velocity and CPP with HOB are twofold, with a decrease in CBF and CPP upon HOB elevation in some studies and without any variation in CBF velocity with HOB elevation from 0° to 30° in others [13][14][15][16]. In a study on postoperative brain surgery patients, there was an initial reduction in CBF velocity with HOB elevation up to 45° [17]. ...
... In another study, there was no change in CBF velocity in various HOB positions at 0° to 90° in SAH patients when assessed after 72 hours [15]. A study on severe TBI patients showed ICP reduction without any variations in MAP, CPP, and cerebral oxygenation (assessed by invasive monitors such as jugular venous oxygen saturation (SjvO2) and brain tissue oxygen tension (PbtO2)) at HOB 30° [16]. We made an attempt to ensure CBF adequacy at HOB 30° and 60° by monitoring rSO2 using NIRS, thereby trying to add credibility to the results of our study. ...
Objectives: Nursing postoperative neurosurgical patients with head of bed (HOB) elevation beyond 30° might be desired at times to prevent pulmonary complications. Due to the paucity of studies determining the effect of HOB beyond 30° on cerebral perfusion pressure (CPP), cerebral blood flow (CBF), and regional cerebral oxygenation (rSO2), this study was designed.
Methods: A total of 40 patients following elective neurosurgery for supratentorial tumors were studied in the neurosurgical intensive care unit three hours following admission. They were assessed for CBF velocities of middle cerebral arteries on either side using transcranial color Doppler (TCCD), rSO2 using near-infrared spectroscopy (NIRS), and mean arterial pressure measured at tragus level at various HOB positions. The estimated cerebral perfusion pressure (CPPe) was calculated from TCCD parameters, and the estimated intracranial pressure (ICPe) was then derived. Their variations at different HOB positions were noted.
Results: TCCD parameters such as peak systolic velocity (PSV) and mean flow velocity (MFV) did not significantly vary upon elevating HOB from 0° to 30° but reduced significantly when HOB was further elevated to 60° (p < 0.05). ICPe reduced significantly with a change of HOB positions from 0° to 60° (p < 0.001), and a significant reduction in CPPe was noticed when HOB was elevated to 60° (67.2 ± 10.1 mmHg vs. 74.7 ± 11.2 mmHg at 0°). However, none of these HOB positions affected rSO2 values.
Conclusion: Postoperative nursing with positions up to 60° HOB can be tried in indicated patients following elective neurosurgery when complemented with CBF velocity and rSO2 monitoring and in whom CPP-guided therapy is not preferred.
... Feldman et al demonstrated among 22 patients with severe traumatic brain injury (TBI) that head elevation to 30°reduced ICP significantly without affecting CPP or cerebral blood flow (CBF). 1 Similarly, Ng et al showed consistent ICP reductions without adverse effect on CPP or brain oxygenation in a study with 38 patients with severe TBI. 2 This beneficial effect has also been demonstrated during craniotomy. 3 The concept of maximizing the effect of head elevation on improving ICP has been taken to the extreme in a recent small series of patients by Lachance et al. 4 Six patients were maintained in vertical position on a specialized bed, in addition to standard ICP control measures. ...
... cially from head elevation in patients with raised ICP. 2 However, consistent effect between head elevation and CPP parameters requires intact autoregulation 8 although in reality, many severe disease processes impair the latter. Some interesting aspects of these parameters of compliance and autoregulation have been investigated. ...
BACKGROUND
Facilitation of venous outflow from the brain is largely believed to be responsible for the beneficial effect of head elevation on intracranial pressure (ICP). However, the impact on cerebral perfusion pressure can be deleterious. Although the adverse effect of obstructing venous outflow in the setting of intracranial hypertension is well documented, the converse (improvement with augmented drainage) has not been demonstrated. Our hypothesis is that the effect of active augmentation of cerebral venous outflow on ICP, although unknown, could be potentially beneficial under conditions of intracranial hypertension.
METHODS
Published literature was perused to ascertain known relationships between head elevation, ICP, cerebral perfusion pressure, and the cerebral venous system.
RESULTS
Head elevation benefits ICP control in intracranial hypertension from improved venous outflow via various networks and craniospinal cerebrospinal fluid displacement; but patients on the severe spectrum have a high likelihood of experiencing cerebral perfusion pressure decline especially beyond 30°. In addition, the interaction between autoregulation, compliance, head elevation, ICP pulse amplitude, cerebral perfusion pressure, and ICP becomes increasingly dyssynchronous in the severely affected brain. Although the detrimental effects of obstructing venous drainage are well documented, the possibility of augmenting venous outflow by withdrawal of sagittal sinus blood has not been described previously.
CONCLUSION
There could exist a potential role for targeted sagittal sinus venous aspiration in favorably influencing control of increased ICP conditions, without significant risk to cerebral perfusion.
... In order to improve patients outcome, head and thorax elevation, so-called head-up position, was shown to strongly reduce ICP while enhancing cerebral perfusion pressure in patients presenting severe traumatic brain injury (7,8). Similar benefits were observed in animal models of cardiac arrest with conventional CPR (9)(10)(11). ...
... Here, we used the same sequence of elevation to test its effect during E-CPR. Importantly, the ability of a head-up position to decrease ICP in other conditions than post-cardiac arrest is also well demonstrated, e.g., in patients presenting trauma brain injury (7)(8). This effect is believed to be related to improved cerebral venous return and redistribution of the cerebro-spinal fluid into the subarachnoid spinal. ...
Aim:
Head and thorax elevation during cardio-pulmonary resuscitation improves cerebral hemodynamics and ultimate neurological outcome after cardiac arrest. Its effect during extracorporeal cardiopulmonary resuscitation (E-CPR) is unknown. We tested whether this procedure could improve hemodynamics in swine treated by E-CPR.Methods and ResultsPigs were anaesthetized and submitted to 15 min of untreated ventricular fibrillation followed by E-CPR. Animals randomly remained in flat position (flat group) or underwent head and thorax elevation since E-CPR institution (head-up group). Electric shocks were delivered after 30 min until return of spontaneous circulation (ROSC). They were followed during 120-min after ROSC. After 30 min of E-CPR, ROSC was achieved in all animals, with no difference regarding blood pressure, heart rate and extra-corporeal membrane of oxygenation flow among groups. The head-up group had an attenuated increase in ICP as compared to the flat group following cardiac arrest (13 ± 1 vs 26 ± 2 mmHg at the end of the follow-up, respectively). Cerebral perfusion pressure tended to be higher in the head-up vs flat group despite not achieving statistical difference (66 ± 1 vs 46 ± 1 mmHg at the end of the follow-up). Carotid blood flow and cerebral oxygen saturation were not significantly different among groups.
Conclusions:
During E-CPR, head and thorax elevation prevents ICP increase. Whether it could improve the ultimate neurological outcome in this situation deserves further investigation.
... As venous pressures and ICP decreased, perfusion pressures increased.All parameters showed positive changes with each heads-up angle elevation increase of 10°(increased CerPP, oxygenation, cerebral blood flow, decreased ICP, and venous pressures). Ng et al.18 found that ICP significantly reduced at 30°compared to the supine position, with cerebral perfusion pressure showing minimal elevation from 0°t o 30°. Mean arterial pressure, global venous cerebral oxygenation along regional cerebral oxygenation remained consistent during the elevation of the head.18 ...
... Ng et al.18 found that ICP significantly reduced at 30°compared to the supine position, with cerebral perfusion pressure showing minimal elevation from 0°t o 30°. Mean arterial pressure, global venous cerebral oxygenation along regional cerebral oxygenation remained consistent during the elevation of the head.18 On the contrary, Park et al.19 showed that heads-up CPR in swine models was associated with decreased rates of ROSC compared to supine position. ...
Background and Aim
Cardiopulmonary resuscitation (CPR) in full‐coded patients requires effective chest compressions with minimal interruptions to maintain adequate perfusion to the brain and other vital organs. Many novel approaches have been proposed to attain better organ perfusion compared to traditional CPR techniques. The purpose of this review is to investigate the safety and efficacy of heads‐up CPR versus supine CPR.
Methods
We searched PubMed Central, SCOPUS, Web of Science, and Cochrane databases from 1990 to February 2021. After the full‐text screening of 40 eligible studies, only seven studies were eligible for our meta‐analysis. We used the RevMan software (5.4) to perform the meta‐analysis.
Results
In survival outcome, the pooled analysis between heads‐up and supine CPR was (risk ratio = 0.98, 95% confidence interval [CI] = 0.17–5.68, p = 0.98). The pooled analyses between heads‐up CPR and supine CPR in cerebral flow, cerebral perfusion pressure and coronary perfusion pressure outcomes, were (mean difference [MD] = 0.10, 95% CI = 0.03–0.17, p = 0.003), (MD = 12.28, 95% CI = 5.92–18.64], p = 0.0002), and (MD = 8.43, 95% CI = 2.71–14.14, p = 0.004), respectively. After doing a subgroup analysis, cerebral perfusion was found to increase during heads‐up CPR compared with supine CPR at 6 min CPR duration and 18 to 20 min CPR duration as well.
Conclusion
Our study suggests that heads‐up CPR is associated with better cerebral and coronary perfusion compared to the conventional supine technique in pigs' models. However, more research is warranted to investigate the safety and efficacy of the heads‐up technique on human beings and to determine the best angle for optimization of the technique results.
... Therapeutic head positioning has beneficial effects on brain physiology in severe TBI [15]. In neurosurgical critical care units, the head of bed (HOB) is elevated to reduce ICP and maintain sufficient CPP [16,17,18,19,20,21]. ...
... Maintaining an adequate cerebral perfusion pressure (CPP) is crucial in patients with a traumatic brain injury. Several studies examined the effects of different head of bed elevations and body positions on ICP and CPP [16,17,19,21]. The beneficial effect of head of bed elevation at 30º in patients with traumatic brain injury has been well established. ...
Background: Traumatic Brain Injury (TBI) is a major cause of morbidity and mortality worldwide. Patients with TBI may need mechanical ventilation because they cannot clear their airway secretions due to decreased consciousness, loss of laryngeal reflexes and an inability to cough. Endotracheal suctioning is important and needed in mechanically ventilated patients for airway clearance, improvement of oxygenation and prevention of atelectasis and infection. However, endotracheal suctioning is an invasive procedure and adversely affects some physiological indicators, such BP, PaO2, O2 saturation, HR, ICP and CPP. Aim: To examine the effect of positioning during endotracheal suctioning on cerebral perfusion pressure among mechanically ventilated patients with traumatic brain injury. Design: A quasi-experimental design (Study-Control) was used. Setting: The current study was conducted at the neurosurgical ICUs in Menoufia University Hospital and the teaching hospital in Shebin AL Khom. Sample: A convenient sample of 100 mechanically ventilated patients with traumatic brain injury were recruited from the neurosurgical ICUs. Tools: A Semi Structured Demographic Sheet; Physiological Measures Recording Sheet including CPP; MAP; CVP and Oxygenation as indicated by ABGs values; and Glasgow Coma Scale (GCS). Results: There was a highly statistically significant increase in CPP (84.30± 6.35, 74.80±8.20) in the study group compared with the control group after endotracheal suctioning and elevating head of bed (HOB) at 30 degrees respectively (P=0.001). Furthermore, there was a statistically significant increase in PaO2 (88. 57±11.50; 73.57±11.24) in the study group compared to the control group after suctioning respectively (P<.05). Also, there was a statistically significant increase in SaO2 (97.43± 2.88, 88.67± 1.72) in the study group compared to the control group after suctioning respectively (P<.05). Recommendations: Initiate the development of clinical practice guidelines for critical care nurses to use head of bed elevation of 30 degrees as routine care during endotracheal suctioning to improve cerebral pressure perfusion and oxygenation for patients with traumatic brain injury.
... It has been extensively investigated in different subgroups of critically ill patients [9,10]. PLR is supposed to be potentially harmful in the acute phase of acute brain injury (ABI) with unstable intracranial hypertension, since the postural change of the head may increase cerebral blood flow and, in turn, the intracranial pressure (ICP) [10][11][12]. However, its use may be still valuable in the following stabilization phase of ABI for adequately titrating daily fluid balance. ...
Background
The use of the passive leg raising (PLR) is limited in acute brain injury (ABI) patients with increased intracranial pressure (ICP) since the postural change of the head may impact on ICP and cerebral autoregulation. However, the PLR use may prevent a positive daily fluid balance, which had been recently associated to worse neurological outcomes. We therefore studied early and delayed effects of PLR on the cerebral autoregulation of patients recovering from ABI.
Materials and methods
This is a Prospective, observational, single-center study conducted in critically ill patients admitted with stable ABI and receiving invasive ICP monitoring, multimodal neuromonitoring and continuous hemodynamic monitoring. The fluid challenge consisted of 500 mL of crystalloid over 10 min; fluid responsiveness was defined as cardiac index increase ≥ 10%. Comparisons between different variables at baseline and after PLR were made by paired Wilcoxon signed-rank test. The correlation coefficients between hemodynamic and neuromonitoring variables were assessed using Spearman’s rank test.
Results
We studied 23 patients [12 patients (52.2%) were fluid responders]. The PLR significantly increased ICP [from 13.7 (8.3–16.4) to 15.4 (12.0–19.2) mmHg; p < 0.001], cerebral perfusion pressure (CPP) [from 51.1 (47.4–55.6) to 56.4 (49.6–61.5) mmHg; p < 0.001] and the pressure reactivity index (PRx) [from 0.12 (0.01–0.24) to 0.43 (0.34–0.46) mmHg; p < 0.001]. Regarding Near Infrared Spectroscopy (NIRS)-derived parameters, PLR significantly increased the arterial component of regional cerebral oxygen saturation (O 2 Hbi) [from 1.8 (0.8–3.7) to 4.3 (2.5–5.6) μM cm; p < 0.001], the deoxygenated hemoglobin (HHbi) [from 1.6 (0.2–2.9) to 2.7 (1.4–4.0) μM cm; p = 0.007] and total hemoglobin (cHbi) [from 3.6 (1.9–5.3) to 7.8 (5.2–10.3): p < 0.001]. In all the patients who had altered autoregulation after PLR, these changes persisted ten minutes afterwards. After the PLR, we observed a significant correlation between MAP and CPP and PRx.
Conclusions
In ABI patient with stable ICP, PLR test increased ICP, but mostly within safety values and thresholds. Despite this, cerebral autoregulation was importantly impaired, and this persisted up to 10 min after the end of the maneuvre. Our results discourage the use of PLR test in ABI even when ICP is stable.
... Based on Newton's second law of motion, positioning the patient with their head towards the back of the aircraft may theoretically improve venous return to the heart and cardiac output. However, for patients with head trauma or acute neurological injuries, a 30° head elevation is recommended to decrease intracranial pressure and improve cranial perfusion pressure [35,36]. Conversely, negative longitudinal accelerations could be harmful if patients with head injuries were positioned with their heads at the rear of the aircraft, potentially increasing intracranial pressure. ...
Background
Helicopter evacuation is crucial for providing medical care to casualties. Previous civilian studies have demonstrated that air transport can enhance survival rates compared with ground transport. However, there has been limited research on specific accelerations during helicopter flights, particularly in military flights. This study aims to analyse and compare the accelerations endured during civilian and military helicopter evacuations.
Methods
Accelerations were recorded during evacuation flights from the site of injury to the first medical responders in civilian helicopter EC135 T1, and military Puma SA.330 and Caiman NH90 TTH helicopters. The research investigated global acceleration and compared acceleration distributions along the vertical, lateral and longitudinal axes. A specific comparative study of the take-off phases was also performed.
Results
The analysis showed that vertical loads caused the most extreme accelerations for all types of helicopter but these extreme accelerations were rare and lasted for less than 1 s. Military flights show similar acceleration intensities to civilian flights, but accelerations are higher during short periods of the take-off phase.
Conclusions
The findings suggest that helicopter evacuations during military operations are as safe as civilian evacuations and highlight the importance of patient positioning in the aircraft. However, further research should investigate the haemodynamic response to accelerations experienced during actual evacuation flights.
... However, this position leads to elevated ICP due to brain edema. On the other hand, HBE can reduce IH due to venous return improvement and CSF distribution to the subarachnoid spinal space [31] . A quasi-experimental, prospective study of 33 patients with acute neurological conditions was conducted to compare different body and head positions. ...
Background
In underdeveloped countries, there is a greater incidence of mortality and morbidity arising from trauma, with traumatic brain injury (TBI) accounting for 50% of all trauma-related deaths. The occurrence of elevated intracranial pressure (ICP), which is a common pathophysiological phenomenon in cases of TBI, acts as a contributing factor to unfavorable outcomes. The aim of this systematic review is to analyze the existing literature regarding the management of adult TBI with raised ICP in an intensive critical care unit, despite limited resources.
Methods
This systematic review was performed in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis protocol. Search engines such as PubMed, the Cochrane database, and Google Scholar were utilized to locate high-level evidence that would facilitate the formation of sound conclusions.
Result
A total of 11 715 articles were identified and individually assessed to determine their eligibility for inclusion or exclusion based on predetermined criteria and outcome variables. The methodological quality of each study was evaluated using recommended criteria. Ultimately, the review consisted of 51 articles.
Conclusion
Physical examination results and noninvasive assessments of the optic nerve sheath diameter (ONSD) via sonography are positively associated with elevated ICP, and are employed as diagnostic and monitoring tools for elevated ICP in resource-limited settings. Management of elevated ICP necessitates an algorithmic approach that utilizes prophylactic measures and acute intervention treatments to mitigate the risk of secondary brain injury.
... Limited evidence exists about the effect of head position (head of bed) on brain oxygenation, especially when measured with PbtO 2 . Better CPP after CPR without changing cerebral oxygenation in the head-up position [34] resembles the results of other studies in patients with TBI and stroke that suggested that elevating the head up to 30 °C induced a reduction of ICP without changing PbtO 2 [78][79][80][81]. On the contrary, a recent study found that from the head-up position to the supine position, both brain tissue oxygenation and ICP tended to increase, suggesting that an individualized approach guided by multimodal neuromonitoring is recommended in patients with ABI [82]. ...
Background:
Cardiac arrest (CA) is a sudden event that is often characterized by hypoxic-ischemic brain injury (HIBI), leading to significant mortality and long-term disability. Brain tissue oxygenation (PbtO2) is an invasive tool for monitoring brain oxygen tension, but it is not routinely used in patients with CA because of the invasiveness and the absence of high-quality data on its effect on outcome. We conducted a systematic review of experimental and clinical evidence to understand the role of PbtO2 in monitoring brain oxygenation in HIBI after CA and the effect of targeted PbtO2 therapy on outcomes.
Methods:
The search was conducted using four search engines (PubMed, Scopus, Embase, and Cochrane), using the Boolean operator to combine mesh terms such as PbtO2, CA, and HIBI.
Results:
Among 1,077 records, 22 studies were included (16 experimental studies and six clinical studies). In experimental studies, PbtO2 was mainly adopted to assess the impact of gas exchanges, drugs, or systemic maneuvers on brain oxygenation. In human studies, PbtO2 was rarely used to monitor the brain oxygen tension in patients with CA and HIBI. PbtO2 values had no clear association with patients' outcomes, but in the experimental studies, brain tissue hypoxia was associated with increased inflammation and neuronal damage.
Conclusions:
Further studies are needed to validate the effect and the threshold of PbtO2 associated with outcome in patients with CA, as well as to understand the physiological mechanisms influencing PbtO2 induced by gas exchanges, drug administration, and changes in body positioning after CA.
... The body of work examining the relationship between head positioning and intracranial hemodynamics demonstrates that among patients with increased ICP, positioning the head from 0° to 30° significantly reduces ICP, [27][28][29][30][31][41][42][43][44][45][46][47][48] although most of these studies included traumatic brain injury patients with few ICH cases enrolled. Findings from a large cohort of consecutive ICH cases found that only 24% of patients underwent ICP monitoring; however, 70% of these experienced at least one episode of ICP reaching values greater than 20 mmHg, 49 raising concern that increased ICP may occur in many patients without objective confirmation of its presence. ...
Background
Prior to the conduct of the Head Position in Stroke Trial (HeadPoST), an international survey ( n = 128) revealed equipoise for selection of head position in acute ischemic stroke.
Objectives
We aimed to determine whether equipoise exists for head position in spontaneous hyperacute intracerebral hemorrhage (ICH) patients following HeadPoST.
Design
This is an international, web-distributed survey focused on head positioning in hyperacute ICH patients.
Methods
A survey was constructed to examine clinicians’ beliefs and practices associated with head positioning of hyperacute ICH patients. Survey items were developed with content experts, piloted, and then refined before distributing through stroke listservs, social media, and purposive snowball sampling. Data were analyzed using descriptive statistics and χ ² test.
Results
We received 181 responses representing 13 countries on four continents: 38% advanced practice providers, 32% bedside nurses, and 30% physicians; overall, participants had median 7 [interquartile range (IQR) = 3–12] years stroke experience with a median of 100 (IQR = 37.5–200) ICH admissions managed annually. Participants disagreed that HeadPoST provided ‘definitive evidence’ for head position in ICH and agreed that their ‘written admission orders include 30-degree head positioning’, with 54% citing hospital policies for this head position in hyperacute ICH. Participants were unsure whether head positioning alone could influence ICH longitudinal outcomes. Use of serial proximal clinical and technology measures during the head positioning intervention were identified by 82% as the most appropriate endpoints for future ICH head positioning trials.
Conclusion
Interdisciplinary providers remain unconvinced by HeadPoST results that head position does not matter in hyperacute ICH. Future trials examining the proximal effects of head positioning on clinical stability in hyperacute ICH are warranted.
... Nonetheless, several pharmacological and non-pharmacological interventions must be carried out in a timely manner to secure a better prognosis. To facilitate venous drainage, it is recommended that the patient's head of the bed is elevated 30-45° [14,15]. To stimulate vasoconstriction, a brief course of hyperventilation to maintain a PaCO 2 of 30-35 mmHg may also be considered for initial, non-invasive management [14,16,17]. ...
Purpose of Review
Patients with brain and spine tumors are at high risk of presenting cancer-related complications at disease presentation or during active treatment and are usually related to the type and location of the lesion. Here, we discuss presentation and management of the most common emergencies affecting patients with central nervous system neoplastic lesions.
Recent Findings
Tumor-related emergencies encompass complications in patients with central nervous system neoplasms, as well as neurologic complications in patients with systemic malignancies. Brain tumor patients are at high risk of developing multiple complications such as intracranial hypertension, brain herniation, intracranial bleeding, spinal cord compression, and others.
Summary
Neuro-oncologic emergencies require immediate attention and multi-disciplinary care. These emergent situations usually need rapid decision-making and management on an inpatient basis.
... Due to its effectiveness in critically ill pa tients, the PLR represents the key examination for fluid responsiveness [29][30][31], based on the virtual fluid challenge leading to a hydrostatic increase of the mean systemic pressure. Severely headinjured patients have been kept in the headup position to ameliorate the effects of increased ICP [32,33]. Due to the anticipated increased risk of intracranial hyper tension during the maneuver and thereafter, PLR test ing has not yet been implemented in NICUs [21,34]. ...
Introduction:
In critically ill brain-injured patients maintaining balanced fluid management is a crucial part of critical care. Many factors influence the relationship between fluid management, cerebral blood flow and cerebral oxygenation. Passive leg raising (PLR)-induced changes predict fluid responsiveness in the majority of non-neurological ICU patients. In patients with intracranial lesions, PLR testing has been hypothesized to increase intracranial pressure (ICP), although data are lacking. We wanted to investigate the feasibility of PLR with expected intracranial pressure increase, according to the higher cerebral blood volume. This should be self-limiting in patients with intact cerebral autoregulation.
Material and methods:
We prospectively included patients with traumatic brain injury (TBI) or aneurysmal subarachnoid hemorrhage (aSAH) in this pilot trial. PLR was performed within 48 hours after the initial diagnosis and on days 5-8. All patients had ICP monitoring. Absence of intracranial hypertension (defined as ICP < 25 mm Hg) was considered a positive test result.
Results:
Ten patients were recruited for this study. The cohort consisted of 6 male patients with TBI and 4 female patients with aSAH. Mean patient age was 55.6 years (range 35-76). Overall, 18 tests could be performed, of which only one had to be terminated due to temporarily elevated ICP. 9 out of 10 patients had no intracranial hypertension during the acute (mean ICP increase 8.45 mm Hg, range 4-16) or during the subacute phase (mean ICP increase 9.12 mm Hg, range 3-18).
Conclusions:
PLR is feasible in patients with intracranial pathology to assess fluid responsiveness and provide optimized patient volume management without increasing the risk of persistent intracranial hypertension.
... Once prone, use of reverse Trendelenburg to achieve head of bed elevation, and ensuring midline head positioning are simple maneuvers to help decrease ICP by improving cerebral venous return(88, 89) and CSF redistribution(90,91). ICP-CPP balance appears optimized around 30-45°(92)(93)(94). Pillows and wedges can help with head elevation and maintenance of midline position while reducing the impact of abdominal pressure on ICP. ...
Considering the COVID-19 pandemic where concomitant occurrence of acute respiratory distress syndrome (ARDS) and severe acute brain injury (sABI) has increasingly co-emerged, we synthesize existing data regarding the simultaneous management of both conditions. Our aim is to provide readers with fundamental principles and concepts for the management of sABI and ARDS, and highlight challenges and conflicts encountered while managing concurrent disease. Up to 40 percent of patients with sABI can develop ARDS. While there are trials and guidelines to support the mainstays of treatment for ARDS and sABI independently, guidance on concomitant management is limited. Treatment strategies aimed at managing severe ARDS may at times conflict with the management of sABI. In this narrative review, we discuss the physiological basis and risks involved during simultaneous management of ARDS and sABI, summarize evidence for treatment decisions, and demonstrate these principles using hypothetical case scenarios. Use of invasive or non-invasive monitoring to assess brain and lung physiology may facilitate goal-directed treatment strategies with the potential to improve outcome. Understanding the pathophysiology and key treatment concepts for co-management of these conditions is critical to optimizing care in this high-acuity patient population.
... It must remain on the axis in order to avoid compression of the jugular veins. The elevation of the head above the heart level is also important and allows to reduce intracranial pressure (ICP) in brain injured patients [8]. We agree that abdominal pressure release and monitoring should be considered during PP, but we would argue to test the tolerance to an obstacle to cerebral blood outflow before PP to identify patient at risk of IH. ...
... The majority of published reports that examined treatment-related outcomes and variations in treatment protocols excluded patients with neurologic diagnoses (4,23,24). Exclusion of patients with neurologic diagnoses is rooted in literature that supports elevations in ICP and changes in CPP when patients are placed in the prone position (25,26). Historical exclusion of these patients has resulted in a dearth of neurologic literature to support a proven treatment strategy for prone position ventilation in patients with neurologic injury and ARDS, which has been shown to be an underdiagnosed condition in patients admitted to ICUs (27). ...
Objectives:
Prone positioning has been shown to be a beneficial adjunctive supportive measure for patients who develop acute respiratory distress syndrome. Studies have excluded patients with reduced intracranial compliance, whereby patients with concomitant neurologic diagnoses and acute respiratory distress syndrome have no defined treatment algorithm or recommendations for management. In this study, we aim to determine the safety and feasibility of prone positioning in the neurologically ill patients.
Design and setting:
A systematic review of the literature, performed in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analyses 2009 guidelines, yielded 10 articles for analysis. Using consensus from these articles, in combination with review of multi-institutional proning protocols for patients with nonneurologic conditions, a proning protocol for patients with intracranial pathology and concomitant acute respiratory distress syndrome was developed.
Measurements and main results:
Among 10 studies included in the final analysis, we found that prone positioning is safe and feasible in the neurologically ill patients with acute respiratory distress syndrome. Increased intracranial pressure and compromised cerebral perfusion pressure may occur with prone positioning. We propose a prone positioning protocol for the neurologically ill patients who require frequent neurologic examinations and intracranial monitoring.
Conclusions:
Although elevations in intracranial pressure and reductions in cerebral perfusion pressure do occur during proning, they may not occur to a degree that would warrant exclusion of prone ventilation as a treatment modality for patients with acute respiratory distress syndrome and concomitant neurologic diagnoses. In cases where intracranial pressure, cerebral perfusion pressure, and brain tissue oxygenation can be monitored, prone position ventilation should be considered a safe and viable therapy.
... However, HOB positioning studies in adults with severe TBI have demonstrated conflicting results. [11][12][13][14][15][16][17][18][19][20] To date, there has only been one study on the effects of HOB positioning on ICP and CPP in the pediatric population following severe TBI. An analysis of 8 pediatric patients who sustained severe TBI demonstrated that in most but not all cases higher HOB elevation resulted in lower ICP without affecting CPP. ...
OBJECTIVE
Head of bed (HOB) elevation to 30° after severe traumatic brain injury (TBI) has become standard positioning across all age groups. This maneuver is thought to minimize the risk of elevated ICP in the hopes of decreasing cerebral blood and fluid volume and increasing cerebral venous outflow with improvement in jugular venous drainage. However, HOB elevation is based on adult population data due to a current paucity of pediatric TBI studies regarding HOB management. In this prospective study of pediatric patients with severe TBI, the authors investigated the role of different head positions on intracranial pressure (ICP), cerebral perfusion pressure (CPP), and cerebral venous outflow through the internal jugular veins (IJVs) on postinjury days 2 and 3 because these time periods are considered the peak risk for intracranial hypertension.
METHODS
Patients younger than 18 years with a Glasgow Coma Scale score ≤ 8 after severe TBI were prospectively recruited at a single quaternary pediatric intensive care unit. All patients had an ICP monitor placed, and no other neurosurgical procedure was performed. On the 2nd and 3rd days postinjury, the degree of HOB elevation was varied between 0° (head-flat or horizontal), 10°, 20°, 30°, 40°, and 50° while ICP, CPP, and bilateral IJV blood flows were recorded.
RESULTS
Eighteen pediatric patients with severe TBI were analyzed. On each postinjury day, 13 of the 18 patients had at least 1 optimal HOB position (the position that simultaneously demonstrated the lowest ICP and the highest CPP). Six patients on each postinjury day had 30° as the optimal HOB position, with only 2 being the same patient on both postinjury days. On postinjury day 2, 3 patients had more than 1 optimal HOB position, while 5 patients did not have an optimal position. On postinjury day 3, 2 patients had more than 1 optimal HOB position while 5 patients did not have an optimal position. Interestingly, 0° (head-flat or horizontal) was the optimal HOB position in 2 patients on postinjury day 2 and 3 patients on postinjury day 3. The optimal HOB position demonstrated lower right IJV blood flow than a nonoptimal position on both postinjury days 2 (p = 0.0023) and 3 (p = 0.0033). There was no significant difference between optimal and nonoptimal HOB positions in the left IJV blood flow.
CONCLUSIONS
In pediatric patients with severe TBI, the authors demonstrated that the optimal HOB position (which decreases ICP and improves CPP) is not always at 30°. Instead, the optimal HOB should be individualized for each pediatric TBI patient on a daily basis.
... Furthermore, there is little evidence to support the optimal elevation levels for the head of the stretcher during prehospital transport. The contemporary critical care and neurosurgery literature suggest that intensive care patients suffering from traumatic brain injury should have the head of the hospital bed elevated to 30° as a therapeutic adjunct to control intracranial pressure and to minimize complications of aspiration [3,10]. However, a Cochrane review in 2017 called into question the literature supporting this standard practice and recommended clinical outcome trials to be conducted to validate this practice [11]. ...
... The panel identified nine studies which assessed ICP in relation to elevation of the head of the bed [109][110][111][112][113][114][115][116][117]. Compared to supine positioning, ICP was consistently lower in patients at angles of 15 o to as high as 90 o . ...
Background:
Acute treatment of cerebral edema and elevated intracranial pressure is a common issue in patients with neurological injury. Practical recommendations regarding selection and monitoring of therapies for initial management of cerebral edema for optimal efficacy and safety are generally lacking. This guideline evaluates the role of hyperosmolar agents (mannitol, HTS), corticosteroids, and selected non-pharmacologic therapies in the acute treatment of cerebral edema. Clinicians must be able to select appropriate therapies for initial cerebral edema management based on available evidence while balancing efficacy and safety.
Methods:
The Neurocritical Care Society recruited experts in neurocritical care, nursing, and pharmacy to create a panel in 2017. The group generated 16 clinical questions related to initial management of cerebral edema in various neurological insults using the PICO format. A research librarian executed a comprehensive literature search through July 2018. The panel screened the identified articles for inclusion related to each specific PICO question and abstracted necessary information for pertinent publications. The panel used GRADE methodology to categorize the quality of evidence as high, moderate, low, or very low based on their confidence that the findings of each publication approximate the true effect of the therapy.
Results:
The panel generated recommendations regarding initial management of cerebral edema in neurocritical care patients with subarachnoid hemorrhage, traumatic brain injury, acute ischemic stroke, intracerebral hemorrhage, bacterial meningitis, and hepatic encephalopathy.
Conclusion:
The available evidence suggests hyperosmolar therapy may be helpful in reducing ICP elevations or cerebral edema in patients with SAH, TBI, AIS, ICH, and HE, although neurological outcomes do not appear to be affected. Corticosteroids appear to be helpful in reducing cerebral edema in patients with bacterial meningitis, but not ICH. Differences in therapeutic response and safety may exist between HTS and mannitol. The use of these agents in these critical clinical situations merits close monitoring for adverse effects. There is a dire need for high-quality research to better inform clinicians of the best options for individualized care of patients with cerebral edema.
Head elevation is recommended as a tier zero measure to decrease high intracranial pressure (ICP) in neurocritical patients. However, its quantitative effects on cerebral perfusion pressure (CPP), jugular bulb oxygen saturation (SjvO2), brain tissue partial pressure of oxygen (PbtO2), and arteriovenous difference of oxygen (AVDO2) are uncertain. Our objective was to evaluate the effects of head elevation on ICP, CPP, SjvO2, PbtO2, and AVDO2 among patients with acute brain injury.
We conducted a systematic review and meta-analysis on PubMed, Scopus, and Cochrane Library of studies comparing the effects of different degrees of head elevation on ICP, CPP, SjvO2, PbtO2, and AVDO2.
A total of 25 articles were included in the systematic review. Of these, 16 provided quantitative data regarding outcomes of interest and underwent meta-analyses. The mean ICP of patients with acute brain injury was lower in group with 30° of head elevation than in the supine position group (mean difference [MD] − 5.58 mm Hg; 95% confidence interval [CI] − 6.74 to − 4.41 mm Hg; p < 0.00001). The only comparison in which a greater degree of head elevation did not significantly reduce the ICP was 45° vs. 30°. The mean CPP remained similar between 30° of head elevation and supine position (MD − 2.48 mm Hg; 95% CI − 5.69 to 0.73 mm Hg; p = 0.13). Similar findings were observed in all other comparisons. The mean SjvO2 was similar between the 30° of head elevation and supine position groups (MD 0.32%; 95% CI − 1.67% to 2.32%; p = 0.75), as was the mean PbtO2 (MD − 1.50 mm Hg; 95% CI − 4.62 to 1.62 mm Hg; p = 0.36), and the mean AVDO2 (MD 0.06 µmol/L; 95% CI − 0.20 to 0.32 µmol/L; p = 0.65).The mean ICP of patients with traumatic brain injury was also lower with 30° of head elevation when compared to the supine position. There was no difference in the mean values of mean arterial pressure, CPP, SjvO2, and PbtO2 between these groups.
Increasing degrees of head elevation were associated, in general, with a lower ICP, whereas CPP and brain oxygenation parameters remained unchanged. The severe traumatic brain injury subanalysis found similar results.
Following ischemic stroke, substance P (SP)-mediated neurogenic inflammation is associated with profound blood-brain barrier (BBB) dysfunction, cerebral edema, and elevated intracranial pressure (ICP). SP elicits its effects by binding the neurokinin 1 tachykinin receptor (NK1-R), with administration of an NK1-R antagonist shown to ameliorate BBB dysfunction and cerebral edema in rodent and permanent ovine stroke models. Given the importance of reperfusion in clinical stroke, this study examined the efficacy of NK1-R antagonist treatment in reducing cerebral edema and ICP in an ovine model of transient middle cerebral artery occlusion (tMCAo). Anesthetized sheep ( n = 24) were subject to 2-hours tMCAo and randomized ( n = 6/group) to receive early NK1-R treatment (days 1–3 post-stroke), delayed NK1-R treatment (day 5 post-stroke), or saline vehicle. At 6-days post-stroke animals were re-anaesthetized and ICP measured, followed by MRI to evaluate infarction, edema and BBB dysfunction. Following both early and delayed NK1-R antagonist administration, ICP was significantly reduced on day 6 compared to vehicle animals (p < 0.05), accompanied by a reduction in cerebral edema, midline shift and BBB dysfunction (p < 0.05). This study demonstrates that NK1-R antagonist treatment is an effective novel therapy for cerebral edema and elevated ICP following stroke in an ovine model, warranting future clinical evaluation.
Patients with neurologic symptoms are frequently seen in the emergency department and require rapid and thorough evaluation. Appropriate assessment with tailored history-taking, localization of the neurological problem, differential diagnosis, focused testing, and urgent treatment when indicated are essential to prevent patient morbidity. Neurological examination and testing of patients are covered in-depth, along with common neurological presentations using a symptom-based approach, such as coma, dizziness and gait disturbance. Specific neurological disorders are also explored, including traumatic brain injury, ischemic stroke and transient ischemic attack and neurotoxicology. Chapters follow a basic outline, including an introduction and a pearls and pitfalls section, providing a succinct overview and key takeaway points for the busy clinician. This well organized handbook will serve as a concise, valued reference for the clinician to use in assisting the evaluation of the most common neurology related emergency department visits.
El tratamiento adecuado para el SAHS (Síndrome de Apnea-hipopnea del Sueño) es la CPAP (Presión Positiva Continua de las vías respiratorias), que ha evolucionado hasta la aparición de la AutoCPAP (Presión Positiva Continua de las vías respiratorias automática), con mayor confort y prestaciones en los años 90. El aumento progresivo de la utilización de CPAP para el tratamiento del SAHS y los avances tecnológicos experimentados por las APAPs (AutoCPAP), permiten realizar un control remoto y reduce costes respecto a la titulación. Podemos exponer que, en general, la APAP nos aporta la información necesaria para realizar un buen manejo de los pacientes con SAHS, ajustando los parámetros, sin necesidad de titular a los pacientes en los centros sanitarios.
The appropriate treatment for SAHS (Sleep Apnea-Hypopnea Syndrome) is CPAP (Continuous Positive Airway Pressure), which has evolved to the onset of AutoCPAP (Continuous Positive Airway Pressure automatic), with greater comfort and performance in the 90s. The progressive increase in the use of CPAP for the treatment of SAHS and technological advances experienced by APAPs (AutoCPAP), allow a remote control and reduces costs with respect to titling. We can state that, in general, the APAP provides us with the necessary information toperform a good management of patients with SAHS, adjusting the parameters, without need to register patients in health centers.
Gracias a los avances científicos en los últimos años, se ha logrado mejorar la calidad y esperanza de vida de los pacientes con Fibrosis Quística (FQ). Los estudios realizados se centran en prevenir los síntomas y retrasar la aparición de FQ en personas con riesgo de desarrollarla
Thanks to scientific advances in recent years, it has been possible to improve the quality and life expectancy of patients with Cystic Fibrosis (CF). The studies carried out focus on prevent symptoms and delay the onset of CF in people at risk of developing it
El desarrollo de nuevas técnicas quirúrgicas y el aumento del número de cirugías anuales han influido en la actualización de los protocolos sobre los cuidados perioperatorios con el fin de disminuir el riesgo de complicaciones
The development of new surgical techniques and the increase in the number of annual surgeries have influenced the updating of protocols on perioperative care in order to reduce the risk of complications
El número de infecciones asociadas a la manipulación indebida del Catéter Venoso Central (CVC) en medio hospitalario aun es un problema para la práctica de los cuidados en enfermería, ya que según la revisión bibliográfica realizada se siguen diagnosticando numerosos casos de infección secundaria a la implantación del CVC. En esta revisión bibliográfica se concluye que las buenas prácticas de los enfermeros en la manipulación del CVC conducirían a una reducción significativa de las tasas de infección asociadas a la manipulación del CVC y con ello se conseguirá además mejorar las tasas de efectividad de los tratamientos de los pacientes por vía central.
The number of central venous catheter-related infections in hospitals due to an inappropriate use is still a problem to nursing practice. According to the bibliographic review carried out, countless of CVC- based infections continue to be diagnosed. In this bibliographic review we concluded that good nurse practices in CVC manipulation would lead to a significant reduction in the infection rates associated with the manipulation of CVC. Therefore the successful rate of patients treatment by central line would increase
catheter – related infections, nurses, nursing care, critical care, central venous catheter
El drenaje ventricular externo consiste en la colocación de un catéter en el asta frontal del ventrículo lateral, preferiblemente del hemisferio no dominante. Es la manera estándar de monitorizar la presión intracraneal. Su uso es una práctica habitual en unidades de cuidados intensivos, en pacientes con alteraciones neurológicas, y está indicado como herramienta diagnóstica y terapéutica.
An external ventricular drainage (EVD) involves to insert a catheter into the frontal horn of the lateral ventricle of the non-dominant hemisphere whenever possible. It is a standard approach for monitoring intracranial pressure and the most common procedures in intensive care unit for neurocritical patients affected by different illnesses. It is a diagnostic and therapeutic tool.
Justificación: La Hipertensión intracraneal (HIC) se relaciona con la mitad de muertes asociadas a lesiones cerebrales traumáticas, aumentando dicha mortalidad cuanto mayores son los niveles de Presión intracraneal. La medición de la PIC en situaciones de urgencias intrahospitalarias es importante, pero debemos conocer la forma de disminuirla si sospechamos de la misma en el ámbito extrahospitalario, puesto que la medición no es tan viable. Hay gran diversidad de tratamientos, pero es interesante saber cuáles son los más efectivos para elegir adecuadamente en situaciones de urgencia y de esa forma disminuir el riesgo de Hipertensión intracraneal y de mortalidad
Justification: Intracranial Hypertension (ICH) is related to half of the deaths associated with traumatic brain injuries, such mortality increasing the higher the levels of intracranial pressure. The measurement of ICP in intrahospital emergency situations is important, but we must know how to reduce it if we suspect it in the extrahospital setting, since the measurement is not as viable. There is a great diversity of treatments, but it is interesting to know which are the most effective to choose appropriately in emergency situations and thus reduce the risk of intracranial hypertension and mortality.
Care for Complications After Catastrophic Brain Injury
The brain is the center of the nervous system controlling other organs. The brain is characterized by extreme complexity of its structure and delicate texture, which makes it difficult to investigate by invasive methods. The advances in semiconductor manufacturing technology led to the development of implantable microelectromechanical system (MEMS)-based devices that can be implanted into the brain with reduced risk of damage to the brain tissue due to their small size and low stiffness. Such devices are now widely applied in the clinic and brain research for understanding brain functions, diagnosing brain-related diseases, and pursuing innovative therapies. Inevitably, these invasive devices cause damage to the brain tissue, such as wounds, inflammation, and scars, eventually leading to dysfunction of the device. Therefore, it is vital to find an optimal design solution for such devices taking into consideration such parameters as size, stiffness and biocompatibility. In this review, we focus on three main brain applications of such devices: detection of electrical signals, intracranial pressure (ICP), and optogenetics. We summarize the current application scope of such MEMS-based devices in brain research and clinical application, and compare them based on their mechanical and biological properties. The understanding of the device design, methods of application, and current development can support neuroscientists and neurologists to make revolutionary discoveries in the brain research field.
Trauma patients present a unique challenge to anesthesiologists, since they require resource-intensive care, often complicated by pre-existing medical conditions. This fully revised new edition focuses on a broad spectrum of traumatic injuries and the procedures anesthesiologists perform to care for trauma patients perioperatively, surgically, and post-operatively. Special emphasis is given to assessment and treatment of co-existing disease, including surgical management of trauma patients with head, spine, orthopedic, cardiac, and burn injuries. Topics such as training for trauma (including use of simulation) and hypothermia in trauma are also covered. Six brand new chapters address pre-hospital and ED trauma management, imaging in trauma, surgical issues in head trauma and in abdominal trauma, anesthesia for oral and maxillofacial trauma, and prevention of injuries. The text is enhanced with numerous tables and 300 illustrations showcasing techniques of airway management, shock resuscitation, echocardiography and use of ultrasound for the performance of regional anesthesia in trauma.
Objectives:
To determine the effect of endotracheal aspiration at different head heights on oxygenation brain by non-invasive method in neurosurgery intensive care patients.
Background:
Head elevation of mechanical ventilator-dependent neurosurgery patients and the possible risks of endotracheal aspiration are closely related to the clinical conditions of the patients.
Design:
A prospective quasi-experimental study with repetitive measurements in a single group.
Methods:
In the study, neurosurgery intensive care patients were adjusted to a head height of 15, 30 and 45° (n = 46, power analysis %90). Cerebral oxygenation levels were determined with a non-invasive device at each head height before and in the 1st, 5th and 30th min of endotracheal aspiration. Data were collected with Patient Information Form and cerebral oxygenation device based on NIRS technology. This study performed according to the TREND reporting guidelines for non-randomized/quasi experimental study.
Results:
The highest cerebral oxygenation value was obtained at 30 min. The decrease in the cerebral oxygenation levels of the patients was highest in the 1st min after endotracheal aspiration, at a head height of 15 degrees for the right cerebral region and at a head height of 30 degrees for the left cerebral region. The increase in oxygenation of the right and left cerebral regions occurred highest at a head height of 45 degrees.
Conclusions:
The ideal head height should be 45 degrees during and after endotracheal aspiration in regard to maintaining cerebral oxygenation in neurosurgery intensive care patients. It is extremely important to monitor the cerebral oxygenation status of patients, with non-invasive measurement tools during and after endotracheal aspiration, to prevent secondary complications.
Relevance to clinical practice:
This study reveals the importance of raising the head 45 degrees in the best preservation of cerebral oxygenation values in neurosurgery intensive care patients. Intensive care nurses should pay attention to maintaining this head height.
Purpose: Investigate the feasibility of a non-invasive method to evaluate the physical and cognitive repercussions of long-lasting post-concussion effects in professional combat sports athletes. To help athletes return to professional combat, there is a need for unbiased objective tools and techniques used as a prognostic method of recovery after Sport Related Concussion (SRC).
Methods: Six mild Traumatic Brain Injury (mTBI) athletes, age 20 ÷ 43 yr (1 female, 5 males) and 7 not concussed (NC) participants (amateur), age 24 ÷ 38 yr (3 females, 4 males), were tested Inspired/expired gas concentration, Cerebral changes in oxygenated hemoglobin (Δ[HbO 2 ]) and deoxygenated hemoglobin (Δ[HHb]) were measured using near infrared spectroscopy (NIRS) with a 3-step protocol: rest before maximal oxygen uptake (VO 2 max) test, hypercapnia, and recovery after VO 2 max test. The brain oxygenation and respiratory parameters of both sample sets were calculated using a non-parametric test (Mann-Whitney U test). Aerobic fitness outcome was quantified through mean average using the Bruce test. Participants performed Fitt's test using a laptop and analysis of medio-lateral and anterior-posterior range of oscillation was carried out via a force platform Romberg test.
Results: mTBI group showed statistically significant differences in saturated hemoglobin Δ[HbO 2 ] ( p < 0.001) during rest and recovery phase after maximal incremental exercise, in medio-lateral sway eyes open ( p = 0.008, NC 25.35 ± 4.11 mm and mTBI 17.65 ± 4.79 mm). VO 2 max revealed no significant differences between the two groups: NC 47.47 ± 4.91 mTBI 49.58 ± 5.19 ml/kg/min ⁻¹ . The 2 groups didn't differ for maximum power output (NC 220 ± 34, mTBI 255 ± 50 W). End-tidal fractional concentration of O 2 (FetO 2 NC15.20 ± 0.41, mTBI 16.09 ± 0.68) throughout hypercapnia, saturated blood hemoglobin (Δ[HbO 2 ]) revealed significant differences with the mTBI group. No differences emerged from Fitt's test.
Conclusions: It emerges that NIRS is able to reveal differences in long time outcomes of mTBI. The medio-lateral variations cannot be considered as a marker of long-term damage in athletes specifically trained for balance.
Patients with diseases involving the nervous system often require anesthesia for diagnostic imaging, sample collection, or treatment of the disease pathology. Understanding the physiology and pathology of the nervous system is important when considering an anesthetic plan during which the goal should be optimization of cerebral blood flow (CBF) and perfusion and prevention of increases in intracranial pressure (ICP). Certain neurologic conditions may affect ventilatory centers; therefore, adequate oxygenation and ventilation must also be a priority. Opioids are an acceptable choice for premedication and analgesia in neurologic patients, as they have minimal direct effects on CBF and ICP. Intervertebral disc disease and vertebral trauma leading to spinal cord dysfunction are major causes of neurologic injury in smallanimal patients. The goals of anesthetic management should focus on using a balanced, multimodal approach while providing adequate analgesia. Dysautonomia is a rare idiopathic condition characterized by degeneration of neurons in the autonomic nervous system ganglia.
Trotz sich stetig verbessernder Operationstechniken sowie intensivmedizi-nischer und diagnostischer Möglichkeiten betrug die durchschnittliche Komplikationsrate neurochirurgischer Eingriffe laut einer Auswertung von Daten des American College of Surgeons im Zeitraum zwischen 2006 und 2011 ca. 14 %. Intrakranielle Eingriffe zeigten eine mehr als zweifach er-höhte Komplikationsrate verglichen mit Operationen an der Wirbelsäule. Mögliche Folgen sind bleibende neurologische Defizite wie Sprachstörun-gen und motorische Ausfälle mit daraus resultierender Pflegebedürftigkeit bis hin zum Tod des Patienten. Da selbst bei planmäßig verlaufenden Hirn-operationen Komplikationen mit zum Teil verheerenden Folgen für den Pa-tienten auftreten können, ist die Entwicklung neuer Methoden zur frühzeiti-gen Erkennung und Vermeidung von unerwünschten Ereignissen ein wich-tiger Bestandteil der Neurochirurgie. Um das Gehirngewebe nicht zusätz-lich zu schädigen wird ein diagnostisches Werkzeug benötigt, dass nicht-invasiv in Echtzeit ein breites Spektrum der klinisch relevanten Parameter erfasst, eine hohe Messauflösung und -genauigkeit besitzt, einfach in der Handhabung ist und problemlos in den Operationsablauf integriert werden kann. Dadurch soll der Operateur zusätzliche Informationen erhalten, um auf drohende Komplikationen rechtzeitig reagieren zu können. Zu diesem Zweck wurde in dieser Studie ein neuartiges nicht-invasives Messverfah-ren, welches die Prinzipien der Laser-Doppler-Flowmetrie und Gewebe-photospektrometrie vereint, während elektiver supratentorieller Aneurysma-Operationen auf seine klinische Einsatzfähigkeit überprüft. In dieser prospektiven, monozentrischen, nicht randomisierten Studie wur-de mithilfe des nicht-invasiven Laser-Doppler-Gewebephotospektrometers „Oxygen-to-see“ (O2C) in einem standardisierten Verfahren die lokale ze-rebrale Mikrozirkulation von 20 Patienten (15 Frauen, 5 Männer) mit einem medianen Alter von 60 ± 11,7 Jahren während elektiver Eingriffe an supra-tentoriellen Aneurysmen untersucht. Hierbei wurden mittels einer fiberopti-schen Sonde in circa 8 mm Gewebetiefe folgende Parameter bestimmt: Kapillarvenöse Sauerstoffsättigung (SO2); Blutflussgeschwindigkeit (velo) Blutfluss (flow); kapillarvenöser Füllungsdruck (rHb). Es erfolgte soweit möglich die simultane Ableitung somatosensorischer Po-tentiale. Um eine relevante Einflussnahme der Herzkreislaufparameter auf die erhobenen Werte auszuschließen erfolgte eine Korrelationsanalyse zwischen anästhesiologischen Daten und O2C-Werten. Repräsentative Messungen wurden sofort nach Duraeröffnung und damit vor jeglicher weiterer chirurgischer Manipulation über einen medianen Zeit-raum von 88 ± 21,8 Sekunden (Zeitspanne: 60 bis 120 Sekunden) ausge-wertet. Folgende Normwerte für den ausgewählten Sondentyp, angegeben als Median-Werte mit zweifacher Standardabweichung, ergaben sich für die physiologische zerebrale Blutversorgung: SO2: 39 % ± 16,6 %; rHb: 53 ± 18,6 AU; velo: 60 ± 20,4 AU; flow: 311 ± 72,8 AU. Im Weiteren stellte sich der Einfluss chirurgischer Manöver auf die vom O2C-Gerät gemessen Parameter wie folgt dar: Die Platzierung des selbsthaltenden Retraktors führte zu einer Abnahme des SO2-Werts um 17 % ± 29 % (p<0.05), zu einer Steigerung des rHb-Werts um 18 % ± 20 % (p<0.01), zu einer Abnahme des flow um 10 % ± 11 % (p<0.01) und einem gleichbleibendem velo-Wert. Die Retraktor-Entfernung bewirkte bis auf eine ebenfalls registrierte SO2-Erniedrigung gegenteilige Effekte. Bei Erhöhung der Kopfposition um 20 Grad kam es zu einem Anstieg des kapillarvenösen Blutflusses um 11 % ± 11 % (p=0.03), einer Erniedrigung des SO2-Werts um 26 % ± 21 % (p=0.03) sowie einer Erniedrigung des rHb-Werts um 9 % ± 10 % (p=0.22). Die Blutflussgeschwindigkeit blieb gleich. Bei Tieflagerung des Patientenkopfes kam es zu einer Steigerung des rHb-Werts um 24 % ± 34 % (p=0.07) und einer Abnahme des Blutflusses um 6 % ± 11 % (p=0.29). Alle anderen Parameter blieben unverändert. Die Platzierung von Nimodipin getränkten Watten hatte, abgesehen von einer geringfügigen Erhöhung des Blutflusses um 3 % ± 4 % (p=0.04), kei-ne anderweitigen statistisch signifikanten Effekte. Während des gesamten Messzeitraumes zeigte das SEP-Monitoring keine Auffälligkeiten. Es kam weder zu operationstechnischen Komplikationen noch zu neurologischen Defiziten im weiteren Verlauf. In der Korrelationsanalyse der Anästhesiedaten zeigten sich signifikante lineare Zusammenhänge zwischen Flow-Wert und pCO2 mit rs= -0,49 (p=0.03) gemäß einer mäßigen negativen Korrelation, sowie zwischen rHB-Wert und HCO3 mit rs= 0,55 (p=0.01) entsprechend einer deutlichen positi-ven Korrelation. Es zeigte sich kein linearer Zusammenhang zwischen den restlichen erhobenen anästhesiologischen Parameter und den O2C-Werten. Die vorliegende wissenschaftliche Arbeit berichtet über ein neuartiges nicht-invasives Echtzeitverfahren zur intraoperativen Messung der zerebra-len Mikrozirkulation. Mit dem „Oxygen-to-see“-System gelang es, lokale Blutflussparameter während elektiver neurochirurgischer Eingriffe zu be-stimmen. Für den verwendeten Sondentyp wurden Werte der lokalen phy-siologischen Mikrozirkulation ermittelt, um daraus eine Aussage über die Detektionsfähigkeit von Parameterschwankungen während chirurgischer Manipulation abzuleiten. Die Ergebnisse legen nahe, dass Veränderungen in der lokalen zerebralen Mikrozirkulation, welche durch den Einsatz von Retraktoren, die Veränderung der Patientenposition auf dem Operations-tisch sowie die Verwendung von vasodilatativen Medikamenten verursacht werden, mit dem O2C erkannt werden können. Die Ergebnisse der Korrela-tionsanalyse der O2C-Werte und Anästhesiedaten bedürfen einer weiteren Untersuchung. Ein direkter kausaler Zusammenhang und damit eine Beein-flussung der erhobenen Messdaten ist jedoch unwahrscheinlich. Das Gerät konnte im Rahmen dieser Arbeit standardmäßig in den klinikinternen Ablauf integriert werden, ohne die Operationsdauer wesentlich zu verlängern. Un-ter Berücksichtigung der Beschränkungen, welche der Einsatz nicht-invasiver Monitoringverfahren im Allgemeinen und das O2C-System im Speziellen mit sich bringt, könnte dieses Gerät in Zukunft bisherige intrao-perative Neuromonitoringsysteme sinnvoll ergänzen. Teilergebnisse der vorliegenden Arbeit wurden veröffentlicht in: B. Sommer, M. Kreuzer, B. Bi-schoff, D. Wolf, H. Schmitt, I.Y. Eyupoglu, K. Rossler, M. Buchfelder, O. Ganslandt, and K. Wiendieck. Combined Laser-Doppler Flowmetry and Spectrophotometry: Feasibility Study of a Novel Device for Monitoring Local Cortical Microcirculation during Aneurysm Surgery. J Neurol Surg A Cent Eur Neurosurg, 2017. 78(1): p. 1-11.
Cancer can affect the central nervous system in many forms, and most of them are potentially lethal or cause permanent neurological deficits. Early recognition and prompt treatment are crucial steps in the care of neuro-oncological patients, and the attending physician can only offer appropriate care by knowing the mechanisms involved in neuro-oncological emergencies. Herein, we review the direct, indirect, and iatrogenic aspects of central nervous system involvement in cancer patients.
Oxygen is the vital substrate for the maintenance of tissue and cellular homeostasis and brain requests a high demand for oxygen and glucose continuously. Insufficient delivery or reduced cellular utilization of oxygen results in failure of aerobic metabolism and glycolysis. This fact results in the reduction of energy generation and increases the production of by-products like hydrogen ions, carbon dioxide, and lactate, which can lead to cerebral ischemia. Cardiac output and systolic volume are influenced by preload, afterload, and contractility. Adequate assessment of volume status and cardiac output usually assists the rational use of fluids. The aim of treatment should be normotension and euvolemia, to seek for physiological parameters, considering evolutionary parameters and fluid responsiveness. Treatment should aim goal to avoid secondary brain injury and the interruption of the inflammatory cascade, treating early as possible neurosurgical lesions, each with its particularities. Most of the available evidence to date comes from traumatic brain injury studies, but often ends up being extrapolated to other acute brain injuries. Using multimodal monitoring, individualizing neurointensive care to avoid secondary injury and neurological deficit, one can reduce morbidity and mortality in neurocritical patients. Thus, it is important to measure cerebral perfusion pressure and intracranial pressure in acute severe brain injuries, ideally with evaluation of cerebral autoregulation measures. Hemodynamic management may include the use of crystalloids and vasoactive and inotropic drugs. Multimodal monitoring is essential to define the need for the use of this armamentarium in a rational and appropriate manner, without adding morbidity to the neurocritical patient.
Neural function is essential to human existence. Thus, loss of any neural element in the course of a critical illness represents a major loss to a given individual. Neurons or supporting elements may be lost in a small, virtually unnoticeable manner, perhaps manifest as cognitive or behavioral deficit, or there may be widespread selective neuronal loss or tissue infarction with more apparent and disabling deficits. Based on the notion that neural function is the essence of acceptable survival from critical illness, it is crucial for perioperative management to include considerations of neural viability and the impact and interactions of the primary diseases and therapeutics on the nervous system. There are numerous perioperative scenarios where a patient may present with neurologic dysfunction. In a general sense, these scenarios often involve ischemia, trauma, or neuroexcitation. Each of these, as they progressively worsen, at some point typically involve a period of decreased cerebral perfusion pressure (CPP), usually resulting from elevated intracranial pressure, eventually compromising cerebral blood flow sufficiently to produce permanent neuronal loss, infarction, and possibly brain death. A variety of biochemical pathways play a major role. Optimization of perioperative outcome after injury to the central nervous system (CNS) is a multifactorial process requiring skillful and well-informed anesthetic and critical care management. However, none of these interventions is risk-free, and extensive knowledge and expertise are very important to ensure a fine balance between the benefits and risks of specific interventions. By the end of this chapter, the anesthesia provider should have a general understanding of how to address the most commonly encountered complications in the acutely injured central nervous system.
Traumatic brain injury (TBI) is a common cause for death in children and adolescents. The underlying brain injury can be categorized into primary lesions caused by the immediate effects of the trauma and secondary lesions due to inflammation, hypoxia, hypotension, hyperthermia, and other metabolic processes. Modern intensive care lies in the prevention of these secondary lesions by correct patient positioning, monitoring of intracranial pressure with rapid therapy of intracranial hypertension (deep sedation, osmotic therapy, barbiturates, liquor drainage), early neurosurgical intervention, and glucose and temperature control. This chapter summarizes current literature and guidelines for conservative management of TBI patients from shock room to advanced intensive care.
Elevations in intracranial pressure (ICP) constitute neurological emergencies, and a significant amount of time in the neurological critical care unit (NCCU) is spent diagnosing and treating increased ICP. It is pivotal to understand the signs of increased ICP, and treatment should be implemented without delay. Most institutes utilize an algorithmic-based approach for ICP management. This chapter will review the etiologies and diagnosis of increased ICP and will summarize our treatment algorithm. The available evidence for each intervention will be discussed.
The traditional practice of elevating the head in order to lower intracranial pressure (ICP) in head-injured patients has been challenged in recent years. Some investigators argue that patients with intracranial hypertension should be placed in a horizontal position, the rationale being that this will increase the cerebral perfusion pressure (CPP) and thereby improve cerebral blood flow (CBF). However, ICP is generally significantly higher when the patient is in the horizontal position. This study was undertaken to clarify the issue of optimal head position in the care of head-injured patients. The effect of 0 degree and 30 degrees head elevation on ICP, CPP, CBF, mean carotid pressure, and other cerebral and systemic physiological parameters was studied in 22 head-injured patients. The mean carotid pressure was significantly lower when the patient's head was elevated at 30 degrees than at 0 degrees (84.3 +/- 14.5 mm Hg vs. 89.5 +/- 14.6 mm Hg), as was the mean ICP (14.1 +/- 6.7 mm Hg vs. 19.7 +/- 8.3 mm Hg). There was no statistically significant change in CPP, CBF, cerebral metabolic rate of oxygen, arteriovenous difference of lactate, or cerebrovascular resistance associated with the change in head position. The data indicate that head elevation to 30 degrees significantly reduced ICP in the majority of the 22 patients without reducing CPP or CBF.
It has been shown that large increases of ICP can be caused by flexion of the head in patients with posterior fossa tumors (6). Such increases might be harmful in some patients.
We studied the effects of six different head positions on intracranial pressure and cerebral blood flow velocity in six infants with a recent history of asphyxia and eight without. ICP was measured nominvasively using a transfontanel pressure transducer, and CBF was assessed using the continuus-wave Doppler method. We found that ICP was lowest with the head elevated and in the midline (P<0.01), and that ICP was higher in all infants in the dependent position (P<0.001). This increase was significantly greater in those who had had an episode of asphyxia during the 48 to 72 hours prior to the study (P<0.02). Therefore, we recommend a head elevation of 30 degrees in the midline in any infant with increased ICP or at high risk for cerebral injury, and caution against the use of the dependent position in these infants.
▪ Objective: To determine if the semirecumbent position (45-degree angle) decreases aspiration of gastric contents to the airways in intubated and mechanically ventilated patients.
▪ Design: A randomized, two-period crossover trial.
▪ Setting: Respiratory intensive care unit.
▪ Patients: Nineteen patients requiring intubation and mechanical ventilation.
▪ Interventions: Patients were studied in the supine and semirecumbent positions on two separate days.
▪ Measurements: After technetium (Tc)-99m sulphur colloid labeling of gastric contents, sequential radioactive counts in endobronchial secretions were measured at 30-minute intervals over a 5-hour period. Samples of endobronchial secretions, gastric juice, and pharyngeal contents were obtained for qualitative bacterial cultures.
▪ Results: Mean radioactive counts in endobronchial secretions were higher in samples obtained while patients were in the supine position than in those obtained while patients were in the semirecumbent position (4154 cpm compared with 954 cpm; P = 0.036). Moreover, the aspiration pattern was time-dependent for each position: For the supine position, radioactivity was 298 cpm at 30 min and 2592 cpm at 300 min (P = 0.013); for the semirecumbent position, radioactivity was 103 cpm at 30 min and 216 cpm at 300 min (P = 0.04). The same microorganisms were isolated from stomach, pharynx, and endobronchial samples in 32% of studies done while patients were semirecumbent and in 68% of studies done while patients were in the supine position.
▪ Conclusions: We conclude that the supine position and length of time the patient is kept in this position are potential risk factors for aspiration of gastric contents. Elevating the head of the bed for patients who can tolerate the semirecumbent position may be a simple, no-cost prophylactic measure.
After head injury cerebral metabolism falls while cerebral blood flow varies. Arterio-jugular venous oxygen content difference defines the metabolism-to-flow ratio. Continuous measurement of arterial and jugular bulb oxygen saturation allows identification and correction of compromised oxygen supply and enables the response to therapeutic manoeuvres to be monitored.
(C) Lippincott-Raven Publishers.
Cerebrospinal fluid (CSF) pressure was recorded in 149 patients and arterial blood pressure (BP) in 11 patients while moving between lateral and sitting positions. Rapid tilting initiated waves in BP and CSF filling pressure. The postural CSF pressure wave manifested itself either as a transient or as a stationary wave similar to a plateau wave. When patients sat up, transient waves had amplitudes up to 550 and stationary waves up to 1000 mm H2O. When they lay down, transient waves had amplitudes up to 800 mm H2O. Stationary waves were found only among patients with elevated intracranial pressure and a diseased brain. The waves were mainly caused by changes in cerebral blood volume probably reflecting the postural BP wave and brain autoregulation. Most patients with stationary and large transient waves also manifested clinical symptoms. These symptoms were aggravated when a craniospinal block developed in the sitting position, and were reduced or avoided when the tilting was performed slowly over 2 to 3 minutes.
The continuous measurement of jugular venous oxygen saturation (SjvO2) with a fiberoptic catheter is evaluated as a method of detecting cerebral ischemia after head injury. Forty-five patients admitted to the hospital in coma after severe head injury had continuous and simultaneous monitoring of SjvO2, intracranial pressure, arterial oxygen saturation, and end-tidal CO2. Cerebral blood flow, cerebral metabolic rates of oxygen and lactate, arterial and jugular venous blood gas levels, and hemoglobin concentration were measured every 8 hours for 1 to 11 days. Whenever SjvO2 dropped to less than 50%, a standardized protocol was followed to confirm the validity of the desaturation and to establish its cause. Correlation of SjvO2 values obtained by catheter and with direct measurement of O2 saturation by a co-oximeter on venous blood withdrawn through the catheter was excellent after in vivo calibration when there was adequate light intensity at the catheter tip (176 measurements: r = 0.87, p less than 0.01). A total of 60 episodes of jugular venous oxygen desaturation occurred in 45 patients. In 20 patients the desaturation value was confirmed by the co-oximeter. There were 33 episodes of desaturation in these 20 patients, due to the following causes: intracranial hypertension in 12 episodes, hypocarbia in 10, arterial hypoxia in six, combinations of the above in three, systemic hypotension in one, and cerebral vasospasm in one. The incidence of jugular venous oxygen desaturations found in this study suggests that continuous monitoring of SjvO2 may be of clinical value in patients with head injury.
To evaluate the changes in cerebral blood flow (CBF) that occur immediately after head injury and the effects of different posttraumatic lesions on CBF, 61 CBF studies were obtained using the xenon-computerized tomography method in 32 severely head-injured adults (Glasgow Coma Scale score (GCS) less than or equal to 7). The measurements were made within 7 days after injury, 43% in the first 24 hours. During the 1st day, patients with an initial GCS score of 3 or 4 and no surgical mass had significantly lower flows than did those with a higher GCS score or mass lesions (p less than 0.05): in the first 1 to 4 hours, those without surgical mass lesions had a mean CBF of 27 cc/100 gm/min, which rose to 44 cc/100 gm/min by 24 hours. Patients without surgical mass lesions who died tended to have a lower global CBF than did those with better outcomes. Mass lesions were associated with a high global CBF and bihemispheric contusions with the lowest flows. By 24 hours after injury, global blood flow increased in groups that originally had low flows and decreased in those with very high initial flows, such that by 36 to 48 hours, most patients had CBF values between 32 and 55 cc/100 gm/min. Lobar, basal ganglion, and brain-stem blood flow values frequently differed by 25% or more from global averages. Brain-stem CBF varied the most but did not correlate with clinical signs of brain-stem dysfunction. Double studies were performed at two different pCO2 values in 10 patients with various posttraumatic lesions, and the CO2 vasoresponsivity was calculated. Abnormal CO2 vasoresponsivity was found with acute subdural hematomas and defuse cerebral swelling but not with epidural hematomas. In patients without surgical mass lesions, the findings suggest that CBF in the first few hours after injury is often low, followed by a hyperemic phase that peaks at 24 hours. Global CBF values vary widely depending on the type of traumatic brain injury, and brain-stem flow is often not accurately reflected by global CBF values. These findings underscore the need to define regional CBF abnormalities in victims of severe head injury if treatment is intended to prevent regional ischemia.
Previous investigations have suggested that intracranial pressure waves may be induced by reduction of cerebral perfusion pressure (CPP). Since pressure waves were noted to be more common in patients with their head elevated at a standard 20° to 30°, CPP was studied as a function of head position and its effect upon intracranial pressure (ICP).
In 18 patients with varying degrees of intracranial hypertension, systemic arterial blood pressure (SABP) was monitored at the level of both the head and the heart. Intracranial pressure and central venous pressure were assessed at every 10° of head elevation from 0° to 50°. For every 10° of head elevation, the average ICP decreased by 1 mm Hg associated with a reduction of 2 to 3 mm Hg CPP. The CPP was not beneficially affected by any degree of head elevation. Maximal CPP (73 ± 3.4 mm Hg (mean ± standard error of the mean)) always occurred with the head in a horizontal position. Cerebrospinal fluid pressure waves occurred in four of the 18 patients studied as a function of reduced CPP caused by head elevation alone. Thus, elevation of the head of the bed was associated with the development of CPP decrements in all cases, and it precipitated pressure waves in some. In 15 of the 18 patients, CPP was maintained by spontaneous 10- to 20-mm Hg increases in SABP, and pressure waves did not occur if CPP was maintained at 70 to 75 mm Hg or above.
It is concluded that 0° head elevation maximizes CPP and reduces the severity and frequency of pressure-wave occurrence. If the head of the bed is to be elevated, then adequate hydration and avoidance of pharmacological agents that reduce SABP or prevent its rise are required to maximize CPP.
We studied the effects of six different head positions on intracranial pressure and cerebral blood flow velocity in six infants with a recent history of asphyxia and eight without. ICP was measured noninvasively using a transfontanel pressure transducer, and CBF was assessed using the continuous-wave Doppler method. We found that ICP was lowest with the head elevated and in the midline (P less than 0.01), and that ICP was higher in all infants in the dependent position (P less than 0.001). This increase was significantly greater in those who had had an episode of asphyxia during the 48 to 72 hours prior to the study (P less than 0.02). Therefore, we recommend a head elevation of 30 degrees in the midline in any infant with increased ICP or at high risk for cerebral injury, and caution against the use of the dependent position in these infants.
To establish if an optimum level of head elevation exists in patients with intracranial hypertension, the authors examined changes in intracranial pressure (ICP), systemic and pulmonary pressures, systemic flows, and intrapulmonary shunt fraction with the patient lying flat, and then with the head elevated at 15 degrees, 30 degrees, and 60 degrees. Cerebral perfusion pressure (CPP) was calculated. The lowest mean ICP was found with elevation of the head to 15 degrees (a fall of -4.5 +/- 1.6 mm Hg, p less than 0.001) and 30 degrees (a fall of -6.1 +/- 3.5 mm Hg, p less than 0.001); the CPP and cardiac output were maintained. With elevation of the head to 60 degrees, the mean ICP increased to -3.8 +/- 9.3 mm Hg of baseline, while the CPP decreased -7.9 +/- 9.3 mm Hg (p less than 0.02), and the cardiac index also fell -0.25 +/- 0.28 liters/min/sq m (p less than 0.01). No significant change in filling pressures, arterial oxygen content, or heart rate was encountered at any level of head elevation. Therefore, a moderate degree (15 degrees or 30 degrees) of head elevation provides a consistent reduction of ICP without concomitant compromise of cardiac function. Lower (0 degrees) or higher (60 degrees) degrees of head elevation may be detrimental to the patient because of changes in the ICP, CPP, and cardiac output.
Cerebral blood flow (CBF) measurements were made in 75 adult patients with closed head injuries (mean Glasgow Coma Scale score 6.2), using the xenon-133 intravenous injection method with eight detectors over each hemisphere. All patients were studied acutely within 96 hours of trauma, and repeatedly observed until death or recovery (total of 361 examinations). Arteriojugular venous oxygen differences (AVDO 2 ) were obtained in 55 of the patients, which permitted assessment of the balance between metabolism and blood flow, and provided estimates of cerebral metabolic rate for oxygen (CMRO 2 ).
Based on mean regional CBF, the patients were classified into two groups: those who exhibited hyperemia on one or more examinations, and those who had a consistently reduced flow during their acute illness. “Hyperemia” was defined as a normal or supernormal CBF in the presence of coma, a definition that was independently confirmed by narrow AVDO 2 's indicative of “luxury perfusion.” During coma, all patients showed a significant depression in CMRO 2 .
Forty-one patients (55%) developed an acute hyperemia with an average duration of 3 days, while 34 patients (45%) consistently had subnormal flows. Although more prevalent in younger patients, hyperemia was found at all age levels (15 to 85 years). There was a highly significant association between hyperemia and the occurrence of intracranial hypertension, defined as an intracranial pressure above 20 mm Hg. Patients with reduced flow showed little or no evidence of global cerebral ischemia, but instead revealed the expected coupling of CBF and metabolism. The CBF responses to hyperventilation were generally preserved, with the hyperemic patients being slightly more reactive. In 10 patients with reduced flow, hyperventilation resulted in wide AVDO 2 's suggestive of ischemia.
The effect of head position on intracranial pressure (ICP) and intracranial compliance was determined in 19 consecutive ICU patients. Ten had lower ICPs with the head raised 60 degrees, two were lower at 0 degrees, and seven were unchanged. Compliance improved with head elevation in five patients, improved with head lowering in four, and was unchanged in 10. The use of subarachnoid screw devices for compliance measurements was validated by simultaneously recording intraventricular and subarachnoid pressures in four patients. Optimal head positioning for patients with raised ICP should be established individually rather than routinely caring for patients with the head elevated.
Utilizing either a subarachnoid screw or an intraventricular cannula, intracranial pressure was continuously monitored in 24 patients with established or potential neurological impairment of various etiologies. Marked diminution in intracranial pressure was observed in the sitting or semisitting position in the 13 patients with documented intracranial hypertension as well as in the 11 in whom intracranial pressure was not elevated. This sustained effect was noted even when superimposed on intensive medical management of intracranial hypertension.
Early results using cerebral perfusion pressure (CPP) management techniques in persons with traumatic brain injury indicate that treatment directed at CPP is superior to traditional techniques focused on intracranial pressure (ICP) management. The authors have continued to refine management techniques directed at CPP maintenance.
One hundred fifty-eight patients with Glasgow Coma Scale (GCS) scores of 7 or lower were managed using vascular volume expansion, cerebrospinal fluid drainage via ventriculostomy, systemic vasopressors (phenylephrine or norepinephrine), and mannitol to maintain a minimum CPP of at least 70 mm Hg. Detailed outcomes and follow-up data bases were maintained. Barbiturates, hyperventilation, and hypothermia were not used.
Cerebral perfusion pressure averaged 83 ± 14 mm Hg; ICP averaged 27 ± 12 mm Hg; and mean systemic arterial blood pressure averaged 109 ± 14 mm Hg. Cerebrospinal fluid drainage averaged 100 ± 98 cc per day. Intake (6040 ± 4150 cc per day) was carefully titrated to output (5460 ± 4000 cc per day); mannitol averaged 188 ± 247 g per day. Approximately 40% of these patients required vasopressor support.
Patients requiring vasopressor support had lower GCS scores than those not requiring vasopressors (4.7 ± 1.3 vs. 5.4 ± 1.2, respectively). Patients with vasopressor support required larger amounts of mannitol, and their admission ICP was 28.7 ± 20.7 versus 17.5 ± 8.6 mm Hg for the nonvasopressor group. Although the death rate in the former group was higher, the outcome quality of the survivors was the same (Glasgow Outcome Scale scores 4.3 ± 0.9 vs. 4.5 ± 0.7). Surgical mass lesion patients had outcomes equal to those of the closed head-injury group.
Mortality ranged from 52% of patients with a GCS score of 3 to 12% of those with a GCS score of 7; overall mortality was 29% across GCS categories. Favorable outcomes ranged from 35% of patients with a GCS score of 3 to 75% of those with a GCS score of 7. Only 2% of the patients in the series remained vegetative and if patients survived, the likelihood of their having a favorable recovery was approximately 80%. These results are significantly better than other reported series across GCS categories in comparisons of death rates, survival versus dead or vegetative, or favorable versus nonfavorable outcome classifications (Mantel—Haenszel χ ² , p < 0.001). Better management could have improved outcome in as many as 35% to 50% of the deaths.
Both experimental traumatic brain injury and clinical traumatic brain injury appear to render the brain more vulnerable to a second ischemic insult. The mechanisms of enhanced vulnerability to subsequent ischemia appear to include a reduced ability to increase cerebral blood flow in response to hypotension, hypoxemia, or acute anemia and increased tissue sensitivity to ischemia. Although numerous mediators may be involved in increased tissue sensitivity, those that particularly merit investigation include oxygen free radicals, glutamate, arachidonate metabolites, calcium ions, and protein kinase C.
To evaluate a new therapy of posttraumatic brain oedema, with the main concept that opening of the blood-brain barrier upsets the normal brain volume regulation, inducing oedema formation. This means that transcapillary fluid fluxes will be controlled by hydrostatic capillary and colloid osmotic pressures, rather than by crystalloid osmotic pressure. If so, brain oedema therapy should include reduction of hydrostatic capillary pressure and preservation of normal colloid osmotic pressure.
11 severely head injured comatose patients with brain swelling, raised intracranial pressure (ICP), and impaired cerebrovascular response to hyperventilation.
To reduce capillary hydrostatic pressure the patients were given hypotensive therapy (beta 1-antagonist, metoprolol and alpha 2-agonist, clonidine) and a potential precapillary vasoconstrictor (dihydroergotamine). The latter may also decrease cerebral blood volume through venous capacitance constriction. Colloid osmotic pressure was maintained by albumin infusions. The concept implies the need of a negative fluid balance with preserved normovolaemia.
ICP decreased significantly within a few hours of treatment with unaltered perfusion pressure in spite of lowered blood pressure. Of 11 patients 9 survived with good recovery/moderate disability, 2 died. This was compared to outcome in a historical control group with identical entry criteria, given conventional brain oedema therapy, where mortality/vegetativity/severe disability was 100%.
The results indicate that the therapy should focus on extracellular rather than intracellular oedema and that ischemia is not the main triggering mechanism behind oedema formation. We suggest that our therapy is superior to conventional therapy by preventing herniation during the healing period of the blood-brain barrier.
The relationship of jugular venous desaturation and neurological outcome was examined in 116 patients with severe head injury. Seventy-six episodes of jugular venous desaturation were prospectively identified in 46 (40%) of the patients. The etiology of the desaturations varied, including both systemic and cerebral causes. A poor neurological outcome was strongly associated with the occurrence of jugular venous desaturation.
Elevation of the head as a common practice to reduce raised intracranial pressure (ICP) has been discussed controversially of late. Some investigators were able to show that besides lowering ICP head elevation may also reduce cerebral perfusion pressure (CPP). For a new evaluation of optimal head position in neurosurgical care it would be of importance to know the influence of body position on cerebral perfusion. We therefore employed continuous jugular venous oximetry, monitoring cerebral oxygenation, to study the effect of 0 degrees, 15 degrees, 30 degrees, and 45 degrees head elevation on ICP, CPP and jugular venous oxygen saturation (SJVO2) in 25 comatose patients with reduced intracranial compliance. As expected, head elevation significantly reduced ICP from 19.8 +/- 1.3 mmHg at 0 degrees to 10.2 +/- 1.2 mmHg at 45 degrees. Already at 30 degrees 92% of the possible effect on ICP was detected. There was no statistically significant change in CPP and SJVO2 associated with varying head position. Individual reactions of CPP to changes in head position, however, were quite unpredictable. The data suggest that an individual approach to head elevation is to be preferred. A moderate head elevation between 15 degrees and 30 degrees significantly reduces ICP and, in general, does not impair cerebral perfusion. Jugular venous oximetry may be used to optimize ICP, CPP and cerebral oxygenation.
Acute subdural hematoma (SDH) remains an important factor in head injury. The early effects of SDH on cerebral blood flow (CBF) and cerebral metabolic rate of oxygen consumption (CMRO2) in humans have not been clearly demonstrated. Patients admitted to the Medical College of Virginia with severe closed-head injury between 1982 and 1990 were studied with Xenon-133 regional CBF measurement. Data were reviewed retrospectively with regard to the presence of SDH (n = 54). A comparison group consisted of patients with head injuries without mass lesions or midline shift on admission computed tomographic scans (n = 76). CBF measurements made in patients less than 16 years of age, with concurrent administrations of mannitol or vasopressors, or with cerebral perfusion pressure under 50 mm Hg were excluded. CBF measurements were made on multiple occasions during the first 6 days after injury, and in many instances, simultaneous determinations of cerebral arteriovenous oxygen difference (AVDO2) were made through sampling of jugular bulb and arterial oxygen content. Not all patients underwent CBF measurements on each day. Differences in mean CBF, CMRO2, and AVDO2 were evaluated on each day after injury with the application of Student's t-test for independent groups. Significant reductions in CBF were demonstrated in patients with SDH on Days 1 (P < 0.0005) and 2 (P < 0.01). CMRO2 differed notably on Days 1 (P < 0.005) and 2 (P < 0.05) in patients with SDH, but when corrected for the lower Glasgow Coma Score in patients with SDH, the P values were only 0.07 and 0.12, respectively (analysis of covariance).(ABSTRACT TRUNCATED AT 250 WORDS)
A simple method of testing cerebral autoregulation by observing transcranial Doppler changes in middle cerebral artery flow velocity (FV) during a brief ipsilateral carotid artery compression (the transient hyperemic response test) was studied in 11 normal healthy volunteers. The aim of this study was to assess the reliability of the method and to compare derived autoregulatory indices with those of a standard noninvasive test of autoregulation, Aaslid's leg-cuff test.
Volunteers were subjected to repeated carotid compressions and leg-cuff tests at different levels of CO2. Hypercapnia was induced using inhalation of a mixture of 5% CO2 in air. Hypocapnia was induced by moderate hyperventilation. To assess the influence of the duration of carotid compression, a series of carotid compressions lasting 3, 4, 5, 7, and 9 seconds were performed in random sequence. Monitored parameters included ipsilateral FV, end-tidal CO2, and arterial blood pressure. The transient hyperemic response ratio (THRR), calculated as the maximum increase of FV divided by baseline values after release of the carotid compression, was taken as the autoregulation index. This index was compared with the rate of autoregulation index derived from the leg-cuff test.
Both tests were significantly associated with end-tidal CO2 (ANOVA, P < .000001 for both carotid compression and cuff test). There was a linear correlation between THRR and autoregulation index (r = .86). However, the reproducibility of the THRR was more consistent than for the autoregulation index from single tests (13% versus 46%, respectively; P < .0001). Although the influence of the duration of carotid compression on THRR values was significant for carotid compressions lasting up to 5 seconds, there was no relation to the relative magnitude of FV drop during the compression.
Brief (> 5 seconds) carotid artery compression provides an index of cerebral autoregulation that is reproducible and is affected by CO2 tension in a fashion similar to autoregulatory indices derived from a standard leg-cuff test. The simplicity of the method provides a potentially useful addition to other noninvasive autoregulation tests for clinical assessments, particularly when repeated measurements are required.
Experimental traumatic brain injury studies have shown that cerebral hyperglycolysis is a pathophysiological response to injury-induced ionic and neurochemical cascades. This finding has important implications regarding cellular viability, vulnerability to secondary insults, and the functional capability of affected regions. Prior to this study, posttraumatic hyperglycolysis had not been detected in humans.
The characteristics and incidence of cerebral hyperglycolysis were determined in 28 severely head injured patients using [ ¹⁸ F]fluorodeoxyglucose—positron emission tomography (FDG-PET). The local cerebral metabolic rate of glucose (CMRG) was calculated using a standard compartmental model. In six of the 28 patients, the global cerebral metabolic rate of oxygen (CMRO 2 ) was determined by the simultaneous measurements of arteriovenous differences of oxygen and cerebral blood flow (xenon-133). Hyperglycolysis, defined as an increase in glucose utilization that measures two standard deviations above expected levels, was documented in all six patients in whom both FDG-PET and CMRO 2 determinations were made within 8 days of injury. Five additional patients were found to have localized areas of hyperglycolysis adjacent to focal mass lesions. Within the 1st week following the injury, 56% of patients studied had presumptive evidence of hyperglycolysis.
The results of this study indicate that the metabolic state of the traumatically injured brain should be defined differentially in terms of glucose and oxygen metabolism. The use of FDG-PET demonstrates that hyperglycolysis occurs both regionally and globally following severe head injury in humans. The results of this clinical study directly complement those previously reported in experimental brain-injury studies, indicating the capability of imaging a fundamental component of cellular pathophysiology characteristic of head injury.
Jugular bulb oximetry provides the first bedside, continuously available information on cerebral perfusion adequacy. An extensive analysis was made of all jugular bulb oxygen saturation (SjO2) data obtained in 50 patients suffering from severe head injury. A total of 176 periods (more than 30 minutes) with reliable, abnormal SjO2-values was observed, with 62 desaturation periods (SjO2 < 55%) and 114 high SjO2-periods (SjO2 > 80%). Jugular desaturation periods were predominantly observed in the first 2 days of monitoring and seemed the most closely correlated to lowered cerebral perfusion pressure and lowered arterial carbon dioxide tension. The high SjO2-values were more equally distributed over the first 5 days of monitoring and seemed mostly correlated to increased arterial carbon dioxide tension. Highlights of the general management of severely head injured patients is discussed, focussing attention on the importance of cerebral perfusion pressure and normoventilation.
It is a common practice to position head-injured patients in bed with the head elevated above the level of the heart in order to reduce intracranial pressure (ICP). This practice has been in vivid discussion since some authors argue a horizontal body position will increase the cerebral perfusion pressure (CPP) and therefore improve cerebral blood flow (CBF). However, ICP is generally significantly higher in the horizontal position. The aim of this study was to evaluate changes in regional microcirculation using tissue pO2 (ti-pO2), as well as changes in cerebral perfusion pressure (CPP) and intracranial pressure induced by changes in body position in patients with head injury. The effect of 0 degree and 30 degrees head elevation on ti-pO2. CPP, ICP and arterial blood pressure (MABP) was studied in 22 head injured patients during day 0-12 after trauma. The mean ICP was significantly lower at 30 degrees head elevation than at 0 degree (14.1 + 8.6 vs. 19.9 + 8.3 mmHg). While MABP was unaffected by head elevation, CPP was slightly higher at 30 degrees than at 0 degree (76.5 + 13.5 vs. 71.5 + 13.2 mmHg). However, regional ti-pO2 was unaffected by body position (30 degrees vs. 0 degree: 24.9 + 13.1 vs. 24.7 + 12.9 mmHg). In addition, there was no change in the time course after trauma concerning these findings in the individual patients. The data indicate that a moderate head elevation of 30 degrees reduces ICP without jeopardizing regional cerebral microcirculation as monitored using a polarographic ti-pO2 microcatheter.
To comparatively assess outcome of patients undergoing monitoring and management of cerebral extraction of oxygen along with cerebral perfusion pressure vs. outcome of patients undergoing monitoring and management of cerebral perfusion pressure alone in severe acute brain trauma.
Prospective, interventional study.
Intensive care unit of a university hospital.
Adults (n = 353) with severe acute brain trauma. A group of 178 patients underwent continuous monitoring and management of cerebral extraction of oxygen and cerebral perfusion pressure, while a control group of 175 patients underwent monitoring and management of cerebral perfusion pressure only.
Routine neuroemergency procedures.
The two groups of patients were matched with regard to age, postresuscitation Glasgow Coma Scale scores, rates of acute surgical intracranial hematomas and brain swelling, pupillary abnormalities, early hypotensive events (before intensive care monitoring), as well as initial levels of intracranial pressure and cerebral perfusion pressure. Outcome at 6 months post injury was significantly better (p < .00005) in the 178 patients undergoing monitoring and management of cerebral extraction of oxygen along with cerebral perfusion pressure, than in the control group of 175 patients undergoing monitoring and management of cerebral perfusion pressure alone.
In patients with severe acute brain trauma and intracranial hypertension associated with compromised cerebrospinal fluid spaces, monitoring and managing cerebral extraction of oxygen in conjunction with cerebral perfusion pressure result in better outcome than when cerebral perfusion pressure is managed alone.
Unlabelled:
Jugular bulb oximetry is the most widely used method of monitoring cerebral oxygenation. More recently, measurement of brain tissue oxygenation has been reported in head-injured patients. We compared the changes in brain tissue oxygen partial pressure (PbO2) with changes in jugular venous oxygen saturation (SjVO2) in response to hyperventilation in areas of brain with and without focal pathology. Thirteen patients with severe head injuries were studied. A multiparameter sensor was inserted into areas of brain with focal pathology in five patients and outside areas of focal pathology in eight patients. A fiberoptic catheter was inserted into the right jugular bulb. Patients were hyperventilated in a stepwise manner from a PaCO2 of approximately 35 mm Hg to a PaCO2 of 22 mm Hg. There was no significant change in cerebral perfusion pressure or arterial partial pressure of oxygen with hyperventilation. In areas without focal pathology, there was a good correlation between changes in SjVO2 and PbO2 (deltaSjVO2 and deltaPbO2; r2 = 0.69, P < 0.0001). In areas with focal pathology, there was no correlation between deltaSjVO, and APbO2 (r2 =0.07, P = 0.23). In this study, we demonstrated that measurement of local tissue oxygenation can highlight focal differences in regional cerebral oxygenation that are disguised when measuring SjVO2. Thus, monitoring of PbO2 is a useful addition to multimodal monitoring of patients with traumatic head injury.
Implications:
Brain oxygenation is currently monitored by using jugular bulb oximetry, which attracts a number of potential artifacts and may not reflect regional changes in oxygenation. We compared this method with measurement of brain tissue oxygenation using a multiparameter sensor inserted into brain tissue. The brain tissue monitor seemed to reflect regional brain oxygenation better than jugular bulb oximetry.
Head elevation as a treatment for lower intracranial pressure (ICP) in patients with intracranial hypertension has been challenged in recent years. Therefore, the authors studied the effect of head position on cerebral hemodynamics in patients with severe head injury.
The effect of 0 degrees, 15 degrees, 30 degrees, and 45 degrees head elevation on ICP, cerebral blood flow (CBF), systemic arterial (PsaMonro) and jugular bulb (Pj) pressures calibrated to the level of the foramen of Monro, cerebral perfusion pressure (CPP), and the arteriovenous pressure gradient (PsaMonro - Pj) was studied in 37 patients who were comatose due to severe intracranial lesions. The CBF decreased gradually with head elevation from 0 to 45 degrees, from 46.3+/-4.8 to 28.7+/-2.3 ml x min(-1) x 100 g(-1) (mean +/- standard error, p<0.01), and the PsaMonro - Pj from 80+/-3 to 73+/-3 mm Hg (p< 0.01). The CPP remained stable between 0 degrees and 30 degrees of head elevation, at 62+/-3 mm Hg, and decreased from 62+/-3 to 57+/-4 mm Hg between 30 degrees and 45 degrees (p<0.05). A simulation showed that the 38% decrease in CBF between 0 degrees and 45 degrees resulted from PsaMonro - Pj changes for 19% of the decrease, from a diversion of the venous drainage from the internal jugular veins to vertebral venous plexus for 15%, and from CPP changes for 4%.
During head elevation the arteriovenous pressure gradient is the major determinant of CBF. The influence of CPP on CBF decreases from 0 to 45 degrees of head elevation.
Backrest positioning for brain-injured adults is variable. Some data support using a flat backrest to optimize cerebral perfusion pressure; other data support elevating the head of the bed at least 30 degrees to reduce intracranial pressure.
To determine whether a flat backrest position or a backrest elevation of 30 degrees provides both optimal cerebral perfusion pressure and optimal intracranial pressure in adults with brain injuries.
A randomized crossover experimental design was used to collect data on 8 adults 18 to 45 years old who had nonvascular, closed-head, traumatic brain injury. Repeated-measures multivariate analysis of variance was used to analyze the data.
Overall, compared with use of a flat/horizontal position, use of a backrest elevation of 30 degrees resulted in significant and clinically important improvements in both intracranial and cerebral perfusion pressures. None of the subjects experienced adverse clinical changes in either intracranial pressure or cerebral perfusion pressure with either backrest position.
The results strengthen the research foundation for raising the backrest position for adults, 18 to 45 years old, who have nonvascular, nonpenetrating, severe brain injuries.
To define optimal cerebral perfusion pressure (CPPOPT) in individual head-injured patients using continuous monitoring of cerebrovascular pressure reactivity. To test the hypothesis that patients with poor outcome were managed at a cerebral perfusion pressure (CPP) differing more from their CPPOPT than were patients with good outcome.
Retrospective analysis of prospectively collected data.
Neurosciences critical care unit of a university hospital.
A total of 114 head-injured patients admitted between January 1997 and August 2000 with continuous monitoring of mean arterial blood pressure (MAP) and intracranial pressure (ICP).
MAP, ICP, and CPP were continuously recorded and a pressure reactivity index (PRx) was calculated online. PRx is the moving correlation coefficient recorded over 4-min periods between averaged values (6-sec periods) of MAP and ICP representing cerebrovascular pressure reactivity. When cerebrovascular reactivity is intact, PRx has negative or zero values, otherwise PRx is positive. Outcome was assessed at 6 months using the Glasgow Outcome Scale. A total of 13,633 hrs of data were recorded. CPPOPT was defined as the CPP where PRx reaches its minimum value when plotted against CPP. Identification of CPPOPT was possible in 68 patients (60%). In 22 patients (27%), CPPOPT was not found because it presumably lay outside the studied range of CPP. Patients' outcome correlated with the difference between CPP and CPPOPT for patients who were managed on average below CPPOPT (r =.53, p <.001) and for patients whose mean CPP was above CPPOPT (r = -.40, p <.05).
CPPOPT could be identified in a majority of patients. Patients with a mean CPP close to CPPOPT were more likely to have a favorable outcome than those whose mean CPP was more different from CPPOPT. We propose use of the criterion of minimal achievable PRx to guide future trials of CPP oriented treatment in head injured patients.
Cerebral perfusion pressure: Management protocol and results.
- Rosner
Reflex control of veins and venous capacitance.
- Rothke
Measuring brain tissue oxygenation compared with jugular venous oxygen saturation for monitoring cerebral oxygenation after traumatic brain injury
- Gupta