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Very not intavenous fluid in the treatment of hypothermia
Abstract
The efficacy and safety of very hot (65 degrees C/149 degrees F) intravenous fluid (IVF) were compared with those of conventional warm (38 degrees C/100.4 degrees F) IVF in the treatment of hypothermia. Eight anesthetized beagles (11-20 kg) were studied. Blood pressure (BP), pulse (P), and core temperature (cT degrees) were recorded at baseline, during hypothermia, and during rewarming. The plasma free hemoglobin (PFHg) was measured to assess hemolysis. Each subject was cooled to 32 degrees C/89.6 degrees F and assigned to receive either 65 degrees C or 38 degrees C IVF via a specially designed multiport balloon-tipped catheter in the superior vena cava (SVC). The IV fluid rate was 80% of the blood volume per hour. Conventional rewarming methods were used in all subjects. After 2 hours the subjects were killed and the SVC was examined for injury. The rate of rewarming was 2.9 degrees C/hour in the 65 degrees C IVF group and 1.25 degrees C/hour in the 38 degrees C IVF group. The cT degrees was significantly different in all subjects after 1 (35.2 degrees +/- 1.03 degrees C vs. 33.2 degrees +/- 0.5 degrees C; p < 0.006) and 2 (37.6 degrees +/- 1.17 degrees C vs. 34.3 degrees +/- 0.9 degrees C; p < 0.004) hours of rewarming. The BP, P, and PFHg were not different. Visual examination of the SVC revealed two lesions in the 65 degrees C IVF group and one in the 38 degrees C group. Mechanical or thermal injury could not be differentiated.(ABSTRACT TRUNCATED AT 250 WORDS)
... In humans and companion animals, hypothermia is often treated with warm saline combined with warming of the skin surface [16][17][18]. Additionally, it is standard practice to use fluids warmed to 37-41 • C to prevent pre-and intra-operative hypothermia in patients [19]. ...
... Additionally, it is standard practice to use fluids warmed to 37-41 • C to prevent pre-and intra-operative hypothermia in patients [19]. Some safety studies in dogs have showed that intravenous (IV) fluid at both 40 • C and 65 • C was a safe and effective means of treating hypothermia [17,18]. Administration of warm IV fluids could be an alternative to providing a heat source that is not stationary and will not reduce stomach space. ...
Piglets are poor at thermoregulation immediately following birth and take up to 24 h to recover from their initial temperature drop. The present study aimed to determine if providing piglets with a 15 mL intraperitoneal injection of warm (45 °C) saline at birth would improve their internal temperature recovery to 24 h of age, and how the treatment interacted with birth weight (BWC = 1; ≤0.80 kg, BWC = 2; 0.81 kg to 1.10 kg, and BWC = 3; >1.10 kg), rectal temperature at 1.5 h (RC = 1; ≤32.0 °C, RC = 2; 32.10 °C to 35.0 °C, and RC = 3; ≥35.10 °C), and colostrum intake (CI = 1; < 200 g and CI = 2, ≥200 g) to affect preweaning survival. Treated BWC1 piglets had improved rectal temperatures from 2 to 24 h. BWC3 piglets who consumed insufficient colostrum also had improved rectal temperature between 1 and 24 h post-birth. Colostrum intake was improved with saline injection in BWC2 piglets of RC1 and RC3 (p < 0.001) and BWC3-RC3 piglets (p < 0.001). Treated BWC1 improved survival to 20 d (p < 0.001). Irrespective of BWC, piglets from all RC had greater survival when injected with saline. The greatest difference was for piglets in RC1, likely due to all BWC1 piglets falling within this category. The results suggest that an intraperitoneal injection of warmed saline is an effective way to improve piglet temperature recovery to 24 h, colostrum intake, and survival in low-birth-weight piglets. These findings will be helpful for producers who have large numbers of low-birth-weight piglets born and are able to provide individual care.
... This is standard practice during surgical operations as well as in cases of severe hypothermia [95]. Administering warm fluids (65 °C) to hypothermic dogs has been shown to increase their temperature with no adverse reactions [96,97]. To our knowledge, there has been no published research on the administration of warm fluids to piglets as a treatment for hypothermia. ...
Increased attention on the effects of the global push for a larger litter size has focused on the increased occurrence of piglets with decreased viability, which have lighter birthweights and a reduced ability to thrive in early life. To improve their odds of survival, interventions must be timely and targeted. This requires the early identification of low-viability pigs and appropriate strategies to manage them. Using novel measures such as abdominal circumference and crown to the rump length in conjunction with birth weight may provide an improved protocol for the identification of those at most risk of preweaning mortality. Further, identifying these at-risk piglets allows interventions to increase their colostrum intake and heat provisions shortly following birth. The appropriate management of the pre- and post-partum sows will improve the chances of decreasing the number of piglets born with lower viability. However, this outcome is constrained by limitations in resources such as technology and staffing. If these challenges can be overcome, it will allow for greater control and increased effectiveness in the implementation of current and new management strategies.
... 19 A recommended prehospital rewarming treatment used by search and rescue teams, emergency medical services, and the military is administration of warmed intravenous fluids (IVF). 3,[19][20][21][22][23] Prior to administration, IVF should be warmed to 38 to 421C, 1-3 as 211C (room temperature) IVF decreases normothermic core temperatures by 0.31C/L. 24 A liter of 401C IVF provides 8 kcal of heat directly into circulating normothermic blood. ...
Objective:
To compare the effectiveness of arteriovenous anastomosis (AVA) vs heated intravenous fluid (IVF) rewarming in hypothermic subjects. Additionally, we sought to develop a novel method of hypothermia induction.
Methods:
Eight subjects underwent 3 cooling trials each to a mean core temperature of 34.8±0.6 (32.7 to 36.3°C) by 14°C water immersion for 30 minutes, followed by walking on a treadmill for 5 minutes. Core temperatures (Δtes) and rates of cooling (°C/h) were measured. Participants were then rewarmed by 1) control: shivering only in a sleeping bag; 2) IVF: shivering in sleeping bag and infusion of 2 L normal saline warmed to 42°C at 77 mL/min; and 3) AVA: shivering in sleeping bag and circulation of 45°C warmed fluid through neoprene pads affixed to the palms and soles of the feet.
Results:
Cold water immersion resulted in a decrease of 0.5±0.5°C Δtes and 1±0.3°C with exercise (P < .01); with an immersion cooling rate of 0.9±0.8°C/h vs 12.6±3.2°C/h with exercise (P < .001). Temperature nadir reached 35.0±0.5°C. There were no significant differences in rewarming rates between the 3 conditions (shivering: 1.3±0.7°C/h, R(2) = 0.683; IVF 1.3±0.7°C/h, R(2) = 0.863; and AVA 1.4±0.6°C/h, R(2) = 0.853; P = .58). Shivering inhibition was greater with AVA but was not significantly different (P = .07).
Conclusions:
This study developed a novel and efficient model of hypothermia induction through exercise-induced convective afterdrop. Although there was not a clear benefit in either of the 2 active rewarming methods, AVA rewarming showed a nonsignificant trend toward greater shivering inhibition, which may be optimized by an improved interface.
... Core warming devices therefore may also have a useful role to play [7]. Intravenous infusion of hot fluids has also been described [8]. Controlling a patient's temperature through the gastrointestinal tract has been accomplished in the past with varying results. ...
. Burns patients are vulnerable to hyperthermia due to sepsis and SIRS and to hypothermia due to heat loss during excision surgery. Both states are associated with increased morbidity and mortality. We describe the first use of a novel esophageal heat exchange device in combination with a heater/cooler unit to manage perioperative hypothermia and postoperative pyrexia.
Material and Methods
. The device was used in three patients with full thickness burns of 51%, 49%, and 45% body surface area to reduce perioperative hypothermia during surgeries of >6 h duration and subsequently to control hyperthermia in one of the patients who developed pyrexia of 40°C on the 22nd postoperative day due to
E. coli
/
Candida
septicaemia which was unresponsive to conventional cooling strategies.
Results
. Perioperative core temperature was maintained at 37°C for all three patients, and it was possible to reduce ambient temperature to 26°C to increase comfort levels for the operating team. The core temperature of the pyrexial patient was reduced to 38.5°C within 2.5 h of instituting the device and maintained around this value thereafter.
Conclusion
. The device was easy to use with no adverse incidents and helped maintain normothermia in all cases.
... L'indication d'un réchauffement interne actif est posée dès lors que l'hypothermie est sévère (< 32°C), que le malade soit ou non en inefficacité circulatoire. Une multitude de moyens de réchauffement internes ont été rapportés, chacun essayant soit d'utiliser une surface d'échange naturelle de l'organisme (poumons par insufflation d'air réchauffé [30] , péritoine par dialyse péritonéale [31] [32] , plèvre par irrigation pleurale à thorax fermé sous thoracoscopie [33] , tube digestif par irrigation oesophagienne [34] ) soit d'apporter une originalité technique (diathermie par ultrasons) [35] , système de réchauffement à haute température des solutés administrés [36] [37] , hémodialyse [38] [39] , réchauffement extracorporel veinoveineux [40] ou artérioveineux [41] continu). Bien qu'il n'existe aucune étude prospective comparative évaluant l'impact du choix de la CEC par rapport à d'autres techniques de réchauffement sur le devenir des patients sévèrement hypothermes, il est largement admis que la circulation extracorporelle demeure en 1997 la méthode de choix pour réchauffer les malades atteints d'hypothermie sévère. ...
Service d'anesthésie et de réanimation chirurgicale, hôpital Bichat, 46, rue Henri-Huchard, 75877 Paris cedex 18 SFAR 97 POINTS ESSENTIELS · L'hypothermie modifie profondément les grandes fonctions physiologiques, et notamment le système cardiovasculaire. · L'hypothermie peut être méconnue devant un tableau clinique orientant vers une autre pathologie organique. Inversement, une hypothermie profonde peut faire partie des symptômes d'une intoxication médicamenteuse. · Le risque vital majeur lié à l'hypothermie est la survenue d'une fibrillation ventriculaire. · La ventilation alvéolaire et l'équilibre acido-basique sont satisfaisants quelle que soit la température chaque fois que les valeurs non corrigées de pH et de PaCO 2 sont maintenues respectivement à 7,4 et 40 mmHg. · L'hypothermie modérée (34 °C) possède des effets neuroprotecteurs bien démontrés in vitro et in vivo. · Devant une inefficacité circulatoire chez un patient en hypothermie profonde, la réanimation cardiorespiratoire doit être effectuée de façon extrêmement prolongée. · En hypothermie, la correction trop rapide d'une hypovolémie peut démasquer une insuffisance cardiaque gauche. · Les interventions thérapeutiques pharmacologiques doivent être limitées et prudentes du fait du retentissement majeur de l'hypothermie sur les grandes fonctions vitales. · En 1997, la méthode de choix pour le réchauffement actif d'un patient atteint d'hypothermie profonde accidentelle reste la circulation extracorporelle. L'hypothermie accidentelle est définie comme une baisse de la température centrale au dessous de 35 °C. Elle est due à la conjonction d'une exposition de l'organisme au froid et d'une incapacité des mécanismes de thermorégulation à maintenir la température centrale à une valeur physiologique. Quelle qu'en soit la cause, l'hypothermie retentit profondément sur les différentes fonctions vitales, notamment sur le système cardiovasculaire. Le problème de la prise en charge thérapeutique est d'opter pour la meilleure modalité de réchauffement en tenant compte du niveau de température atteint, de l'état cardiocirculatoire du patient et des possibilités techniques disponibles rapidement. L'hypothermie accidentelle profonde est considérée comme un événement rare. Cependant, il est vraisemblable que sa fréquence est sous-estimée car cette pathologie est souvent méconnue, notamment du fait de l'insuffisance en moyens diagnostiques performants, et d'une évaluation imprécise dans les systèmes de cotation de la gravité des malades dans les établissements hospitaliers. En outre, il n'est pas exceptionnel que le diagnostic d'hypothermie soit méconnu devant une symptomatologie évoquant une pathologie médicale, traumatique, toxicologique ou neuropsychiatrique [1] [2] . À titre indicatif, 4 826 décès ont été attribués à l'hypothermie aux USA entre 1970 et 1979 [3] . Pour la période de 1979 à 1992, le chiffre avancé est de 10 550 morts dans ce pays, soit environ 750 morts par an [4] . Les facteurs climatiques et le développement de conditions sociales difficiles sont des facteurs favorisants dont l'importance est à souligner [5] . En effet, si une exposition au froid est évidente dans certains cas et permet de simplifier l'approche diagnostique, des tableaux cliniques plus frustes sont fréquemment rencontrés dans les milieux urbains et chez les sujets âgés [1] . L'hypothermie est favorisée par un certain nombre de facteurs qui ont pour effet de diminuer la production de chaleur de l'organisme, d'augmenter les déperditions caloriques ou de perturber directement les systèmes thermorégulateurs. Dans un certain nombre de cas, plusieurs de ces facteurs favorisants sont présents simultanément (tableau I) . Dans cette revue, nous effectuerons un bref rappel physiologique sur les systèmes mis en jeu dans la thermorégulation et les problèmes relatifs à la mesure de la température centrale. Nous discuterons ensuite les conséquences physiopathologiques de l'hypothermie sur les grandes fonctions en insistant sur les perturbations hémodynamiques qui en font toute la gravité. Enfin, nous décrirons les différents tableaux cliniques d'hypothermie accidentelle et discuterons les différentes modalités thérapeutiques.
... Other devices warm intravenous fluids (Standard Ranger, Hotline, Fluido, and Level I) but none of these devices were consistently able to keep the patient's core temperature >36 8C in a recent study [2]. Infusing hot saline (55–60 8C) through central venous catheters during excision and grafting of burn wounds was found to be safe but temperature regulation was limited by the volume of heated crystalloid infused during the surgeries [6]. The CoolGard 3000 TM (Alsius) system is a new temperature regulation device. ...
Staged excision and grafting remains the mainstay of the surgical treatment of large burn injuries since Jackson and colleagues demonstrated a decreased mortality with excisions of 20% or less in 1960 [1]. The major factors limiting these excisions are blood loss and hypothermia. Despite these known limitations, little progress had been made in combating the hypothermia that comes with a large excision. The current re-warming strategies include: increasing ambient room temperature, infusing warm intravenous fluids, and using hot air technologies such as the Bair Hugger (TM), but no single solution or combination of solutions has proven adequate (2). Recently at our institution, a new intravascular warming catheter was used to perform a large burn excision with excellent results.
Mammals regulate body temperature by regulating heat content and distribution (1). To maintain a constant heat content, heat gain or metabolic heat production must equal heat loss. When heat gain or metabolic heat production exceeds heat loss, the total heat content of the body increases, resulting in an increase in mean body temperature. Conversely, the mean body temperature decreases when heat loss exceeds heat gain or metabolic heat production.
Objective: Infusion of cold fluids in a patient leads to a reduction of core temperature and subsequently worsens hypothermia. We evaluated the efficacy of a newly developed self-warming insulation device for use in pre-hospital rescue. Methods: We studied 50 trauma patients with a rescue time of more than one hour. They were randomly assigned to either infusions taken directly from a warming box in the ambulance (Group A, n = 25) or infusions taken from the warming box and packed in an insulation device (Group 13, n = 25). We recorded ambient temperatures, infusion temperatures in five-minute-steps and transport duration of the infusions from the ambulance to the site of accident. Results: Ambient temperatures and transport duration did not differ significantly between both groups. In Group A the infusion temperature decreased from 36.0 +/- 6.4degreesC to 19.8 +/- 6.8degreesC during the transport from the ambulance to the site of accident. In Group B infusion temperature decreased only about 1degreesC. In Group A the temperature of the infusion continued to decrease until the end of measurements. In contrast in Group B the infusion temperature even increased by 0.5degreesC over the measurement period. These differences between the two groups were statistically significant. Conclusions: Our data show that even pre-warmed infusions from a warming box cool down considerably before they can be given to the patient. A self-warming insulation device can stabilize infusion temperature even under extreme conditions of prehospital trauma care.
Accidental hypothermia (core body temparature of less than 35°C) Is a life threatening medical emergency with a high mortality rate. Hypothermia, which Is usually an accidental state, may be caused by social, occupational, recreational, latrogenic and criminal reasons. The prognosis depends on the underlying disease, the severity of frostbite, advanced or very early age, pretreatment state, the severity of haemodynamic deterioration and active external or Internal rewarming methods. Treatment should be continued until the patient reaches the normal body temparature and no patient should be regarded as dead before being totally rewarmed. In this article, the controversies In the treatment of frostbite within the recent years, resuscitation efforts and the potential complications have been revised.
Objective:
To determine if prewarmed intravenous fluids produce superior fluid output temperatures compared with room temperature fluids at common anaesthetic fluid rates for small animal patients.
Methods:
A prospective, randomised, in vitro fluid line test-vein study was performed. Nine flow rates were analysed (10, 20, 60, 100, 140, 180, 220, 260 and 300 mL/hour) for room temperature fluids (21°C) and for five prewarmed fluids (40, 45, 50, 55 and 60°C).
Results:
For each flow rate tested, room temperature fluids never exceeded 25°C at any time point for each trial (range 18 to 25°C). For each flow rate tested, prewarmed fluids never exceeded 25 · 5°C at any time point for each trial (range 18 to 25 · 5°C). The mean output fluid temperature of prewarmed fluids was significantly warmer than room temperature fluids only at 300 mL/hour for 40°C (P = 0 · 0012), 45°C (P = 0 · 004), 50°C (P = 0 · 0002), 55°C (P = 0 · 0001) and 60°C (P < 0 · 0001).
Clinical significance:
There was no thermodynamic benefit to utilising prewarmed intravenous fluids (up to 60°C) compared with room temperature intravenous fluids at common anaesthetic fluid rates for small animals.
Si definisce «ipotermia» una caduta della temperatura corporea al di sotto di 35°C. Questa diminuzione della temperatura si ripercuote su tutte le funzioni dell’organismo. Al di sotto di 32°C, il paziente corre un rischio di vita essenzialmente legato al pericolo di arresto circolatorio. La riduzione del metabolismo tissutale, che accompagna il raffreddamento dell’organismo, protegge il paziente dall’ipossia dovuta all’ipoventilazione e al rallentamento emodinamico. Questa protezione permette di sperare di rianimare senza sequele i pazienti ipotermici che hanno presentato un arresto cardiaco prolungato nel corso della loro gestione, perfino i soggetti ritrovati in stato di morte apparente. In un paziente con un’attività cardiaca conservata, viene applicata in un primo tempo una strategia di «minimo stress». Questa strategia di minimo stress accompagna il riscaldamento spontaneo mediante metodi poco invasivi (coperte ad aria pulsata, riscaldamento delle perfusioni e dell’aria inalata) ed è rivolta a evitare ogni atto terapeutico che rischi di provocare una fibrillazione ventricolare. Se il riscaldamento non è efficace (cioè <1°C/h) è allora consigliata un’irrogazione peritoneale con soluzione fisiologica calda. In caso di arresto cardiaco, la circolazione extracorporea (CEC) con una incannulazione femorale è la metodica di assistenza circolatoria e di riscaldamento più adatta. Per aumentare il tasso di successo dei tentativi di CEC di riscaldamento, è necessario effettuare un triage a monte in aiuto agli algoritmi decisionali fondati su criteri obiettivi. Un paziente che ha una temperatura superiore a 32°C o una kaliemia superiore a 10 mmol/l non sarà proposto per la CEC. Sono in fase di valutazione dei trattamenti come il bretilio, tesi a prevenire la fibrillazione ventricolare, gli shunt vascolari femorali, che permettono di accelerare il riscaldamento spontaneo o, ancora, la CEC senza eparina, che mira a limitare il rischio emorragico.
Trauma is the number one cause of death in children between the ages of 1 and 14 years. Because the appropriate management of traumatized children by all health care providers significantly affects morbidity and survival, it is important to review the care of these children at all stages after the traumatic incident, beginning with a discussion of the initial resuscitative care of the traumatized child.
Objective: To show that resuscitation from hypothermic, hemorrhagic shock using 65 degrees C intravenous fluid results in a more rapid return to euthermia compared with 40 degrees C intravenous fluid, without significant endothelial or hemolytic injury. Design: Fourteen anesthetized beagles (10-12 kg) were cooled to a core temperature of 30 degrees C and hemorrhaged to a mean arterial pressure of 40 to 45 mm Hg for 30 minutes. The animals were randomized to receive either 65 degrees C or 10 degrees C intravenous fluid through a specially designed catheter at a rate of 80% of their blood volume per hour until euthermic (37 degrees C) or for 2 hours. Materials and Methods: Blood pressure, pulmonary artery pressure, heart rate, and core temperature were continuously monitored. Blood samples were collected at baseline, after hemorrhage, 2 hours of resuscitation, and at postmortem examination after 7 days of survival. Laboratory measurements included complete blood count, plasma-free hemoglobin, and osmotic fragility. Values were compared using the Student's paired or unpaired t test with p similar to 0.05 indicating significance. Postmortem examination included light microscopy of the proximal superior vena cava or right atrium, Results: Animals receiving 65 degrees C intravenous fluid warmed 3.6 degrees C/hour, significantly faster than the 40 degrees C animals (1,9 degrees C/hour), There were no significant differences in plasma-free hemoglobin or osmotic fragility. Endothelial injuries were found in two animals in each group, These defects occurred along the path of catheter insertion and not at the infusion site, Conclusions: Central intravenous fluid at 65 degrees C is a more rapid means of treating hypothermia than standard 40 degrees C intravenous fluid, It is safe even in hypothermia animals.
IntroductionHypothermia may be encountered at some time in most parts of Australasia. There is a need to evaluate the merits of the various practical rewarming therapies available.Method
An electronic and manual search of databases to identify randomised trials published between 1966 and 1996 inclusive which evaluated rewarming therapies in hypothermia.ResultsThere is a paucity of randomised trials on this subject and many of the rewarming therapies recommended in authoritative texts and reviews have never been evaluated in randomised clinical trials. In published trials core afterdrop is typically <0.5 C and is least with active core rewarming. Passive rewarming alone may be expected to raise core temperature by 0.75 C/hr and the addition of inhalation and/or forced air rewarming can be expected to at least double this.Conclusions
The choice of rewarming therapy may be largely one of practicality and availability. Future rewarming research should focus on clinical outcomes in patients with moderate to severe hypothermia.
Objective
Infusion of cold fluids in a patient leads to a reduction of core temperature and subsequently worsens hypothermia. We evaluated the efficacy of a newly developed self-warming insulation device for use in pre-hospital rescue.
Methods
We studied 50 trauma patients with a rescue time of more than one hour. They were randomly assigned to either infusions taken directly from a warming box in the ambulance (Group A, n=25) or infusions taken from the warming box and packed in an insulation device (Group B. n=25). We recorded ambient temperatures, infusion temperatures in five-minute-steps and transport duration of the infusions from the ambulance to the site of accident.
Results
Ambient temperatures and transport duration did not differ significantly between both groups. In Group A the infusion temperature decreased from 36.0±6.4°C to 19.8±6.8°C during the transport from the ambulance to the site of accident. In Group B infusion temperature decreased only about 1°C. In Group A the temperature of the infusion continued to decrease until the end of measurements. In contrast in Group B the infusion temperature even increased by 0.5°C over the measurement period. These differences between the two groups were statistically significant.
Conclusions
Our data show that even pre-warmed infusions from a warming box cool down considerably before they can be given to the patient. A self-warming insulation device can stabilize infusion temperature even under extreme conditions of prehospital trauma care
Hypothermia results in vital sign lability, coagulopathy, wound infections, and other sequelae. Normothermia can be restored by several modalities, including passive blanket heating, warm forced-air devices, and active fluid warming (AFW). In AFW, intravenously administered fluids are heated to 40 to 45 °C to minimize net thermal losses and to raise body temperature. Clinical studies have demonstrated the efficacy of AFW as part of a strategy encompassing several methods, but the isolated contribution of AFW to warming has not been theoretically examined in detail.
A calorimetric model is derived to determine the functional dependence of warming on patient weight, hypothermia severity, infusion temperature, and volume infused. A second heat transfer model is derived to describe the time-dependent temperature changes of the periphery and core after warmed-fluid infusion.
There is an inverse linear relationship between the patient's initial temperature and the amount of warming achieved with a given volume. In contrast, as the temperature of the infusion approaches the desired final temperature, the volume required for a fixed temperature change increases nonlinearly. For weight-based boluses, the temperature change scales appropriately with patient mass. Infusion of 2 L of room-temperature crystalloid results in a decrease in body temperature of approximately one-third degree Celsius in the average normothermic adult. For the heat transfer model, previously reported rates of temperature drop and recovery after the intravenous infusion of cold fluids are qualitatively reproduced with a blood mixing time of approximately 15 minutes.
Our calculations reveal that AFW has a larger measurable beneficial effect for patients with more severe hypothermia, but true rewarming of the patient with AFW alone would require prohibitively large fluid volumes (more than 10 L of 40 °C fluid) or dangerously hot fluid (20 mL/kg of 80 °C fluid for a 1 °C increase). The major beneficial effect of AFW is the prevention of further net heat loss.
To evaluate the Warmflo fluid warming system at various flow rates of crystalloid solution simulated to clinical conditions.
Prospective analysis and laboratory investigation.
Operating room and technical laboratory of a university-affiliated hospital.
The Warmflo WF-100 fluid warming (heat exchanger) cassette of the Warmflo FW-538 fluid warming system was primed with lactated Ringer's solution. The fluid warming system was adjusted to temperature set points of 38 degrees C or 42 degrees C. The temperature of the solution flowing through the warming system was measured inside the infusion line downstream from the heat exchanger cassette at the proximal and distal sites, with flow rates of two, 10, and 100 mL/min and simultaneously inside the warming housing between the heater plates.
Average temperature of the solution measured inside the infusion line at the proximal site ranged between 33.4 (+/-1.35) degrees C and 34.0 (+/-2.23) degrees C at a flow rate of two mL/min when the temperature set point was 38 degrees C. At all other flow rates at either set point, the solution temperature was above 37.5 degrees C inside the infusion line, reaching up to 43.9 degrees C at a flow rate of 100 mL/min and a set point of 42 degrees C. Temperatures inside the warming housing ranged from 40.6 (+/-0.26) degrees C to a maximum of 48.0 (+/-0.85) degrees C at a set point of 42 degrees C after the flow stopped.
The Warmflo fluid warming system can overheat fluids at temperatures considerably above normal body temperatures.
Respiratory dysfunction remains one of the major complications after burn surgery in extensively burned patients. We evaluated the relationship between the invasiveness of burn surgery and acute lung injury (ALI).
Patients admitted to our burn unit between 2006 and 2007 with burns greater than or equal to 30% of the total body surface area without severe inhalation injury were entered into this study. Of sixteen patients (mean age, 49.4 +/- 19.3 years, total body surface area 46.0% +/- 14.9%) who underwent burn surgery (3-6 days postburn), vital signs, hemodynamic parameters, blood gas analysis, and peak inspiratory pressure were recorded. Lung injury severity (LIS) score was serially determined. Bronchoalveolar lavage (BAL) was performed before and 24 hour postoperatively.
Body temperature and LIS score preoperatively (baseline) were 37.1 degrees C +/- 0.9 degrees C and 3.8 degrees C +/- 2.2 degrees C, respectively. LIS score increased with increased polymorphonuclear neutrophil in BAL 24 hour postoperatively in 7 of 10 patients with intraoperative temperature decreasing more than 1 degrees C. Extent of excision (20.3% +/- 6.7%), transfusion (4.3 +/- 3.0 units), or duration of surgery (147 +/- 49 minutes) alone did not show significant correlation with the development of ALI postoperatively.
In patients with severe burn injury, hypothermia during surgery despite aggressive intraoperative warming is significantly correlated with the development of ALI with increased polymorphonuclear neutrophil in BAL and may reflect the severity of invasiveness.
To demonstrate the safety and efficacy of 65 degrees C (149 degrees F) centrally administered intravenous fluid (CIVF) compared to conventional 40 degrees C (104 degrees F) CIVF in the treatment of hypothermia.
Ten beagles (9-13 kg) were prospectively randomized to receive 65 degrees C or 40 degrees C CIVF. They were anesthetized and data were collected at baseline, during hypothermia, and after 1 and 2 hours of rewarming. The plasma free/total hemoglobin (PFHb/THb) was measured to detect hemolysis. Each subject was cooled to 30 degrees C (86 degrees F) and then received either 65 degrees C or 40 degrees C CIVF through a specialized catheter in the superior vena cava for 2 hours in addition to conventional rewarming techniques. All subjects survived 7 days, after which they were sacrificed and a complete autopsy was performed.
The rewarming rate was 3.7 degrees C/hr in the 65 degrees C CIVF group and 1.75 degrees C/hr in the 40 degrees C CIVF group. Core temperatures were significantly different after 1 hour (33.4 degrees +/- 0.77 degrees versus 31.7 degrees +/- 0.57 degrees, P < 0.01) and 2 hours (37 degrees +/- 1.03 degrees versus 33.4 degrees +/- 0.89 degrees, P < 0.001). PFHb/THb was not different. Two intimal injuries occurred in each group but these were remote from the infusion site. Blinded examination by two pathologists could not differentiate the etiology of these injuries from mechanical trauma.
CIVF at 65 degrees C is a safe and effective means of treating hypothermia.
Hypothermia exacerbates coagulopathy and is thus a potentially devastating morbidity during operative debridement of burn wounds. Current techniques for maintaining body temperature include warming intravenous fluids at 38 degrees C. The purpose of this study was to assess the safety of infusing saline heated to 55-60 degrees C.
Using a modified fluid warmer, saline heated to 60 degrees C was infused through central venous access in eight adult patients undergoing debridement of burn wounds. The temperature of the saline actually entering the patient was measured by a thermocouple attached at the connection to the central line catheter.
The actual infusate temperature was 54.0 +/- 1.2 degrees C. Over the first hour, 1,100 mL of hot saline was given, thus delivering 17.6 kcal more heat than fluid warmed to the traditional 38 degrees C. Core temperature measured via esophageal and Foley catheters had an insignificant trend toward increase during the operative procedure. There was no evidence of intravascular hemolysis or coagulopathy.
This pilot study suggests that infusion of hot crystalloids given via central venous access is safe and may be an acceptable adjuvant in attenuating hypothermia during operative procedures.
A study was undertaken to determine the relationship between temperature and delivery rate of warmed intravenous fluid using standard intravenous infusion equipment and tubing. One-liter bags of 0.9% NaCl were warmed to 60 degrees C and run through standard microdrip tubing for 1 hour at rates of 1,000, 800, 600, and 400 mL/h. Thermistor probes were placed into the bag and into the tubing at 0, 100, 180, 230, and 280 cm from the intravenous bag. Separate fluid bags were also warmed to 39.3 degrees and 75 degrees C, and the fluid was run through the same apparatus at 1,000 mL/h and 200 mL/h, respectively. Temperatures were recorded at each site at the start of the infusion and every 10 minutes thereafter for 1 hour, Subsequently, 60-mL syringes of fluid warmed to 39.5 degrees C were eluted through 50 cm tubing over 10 minutes at 300 mL/h and 360 mL/h. Mean delivery temperature over each 10-minute infusion was determined. Fluid preheated to 39.3 degrees C approached room temperature at delivery even at a flow rate of 1,000 mL/h and tubing lengths as short as 100 cm. Fluid preheated to 60 degrees C was delivered at near 37 degrees C using tubing lengths as long as 280 cm when eluted at 1,000 mL/h. Fluid preheated to 39 degrees C in 60-mL syringes and eluted through 50 cm of tubing over a period of 10 minutes at 300 mL/h or 360 mL/h was delivered near a mean temperature of 37 degrees C. These results show that warmed fluid can be delivered through standard intravenous tubing at or near 37 degrees C if the fluid is preheated to 60 degrees C and eluted through long tubing (280 cm) at high flow rates (1,000 mL/h). Alternatively, fluid warmed to 37 degrees C to 42 degrees C can be delivered at or near 37 degrees C via intermittent bolus through short tubing (50 cm) either by hand or syringe pump. The latter approach would be particularly beneficial in the pediatric population, in whom it is not advisable to administer fluid at flow rates as high as 1,000 mL/h.
The infusion of warm intravenous fluid (IVF) is a simple and effective method used to maintain or restore core body temperature. At present, 40 degrees C is believed to be the highest temperature that can be safely administered. There is concern that temperatures greater than 40 degrees C may harm blood cells. The mixing time of IVF infused into a high-flow vein such as the superior vena cava is very short, however, approximately 300 milliseconds. We will determine the maximum temperature and exposure time tolerated by human red and white blood cells without producing injury.
Whole blood and isolated neutrophils were exposed to temperatures (40-80 degrees C) for short time intervals (150-1,200 milliseconds). Lethal injury to red and white blood cells was measured by the plasma free hemoglobin and percent viability, respectively. Neutrophil viability was measured by trypan blue staining. Sublethal injury to red and white cells was measured by osmotic fragility and oxidative burst, respectively. Neutrophil oxidative burst was measured by chemiluminescence. Control values were compared with postexposure values using analysis of variance with p < 0.05 indicating significance.
Lethal injury to red blood cells did not occur until exposure at 70 degrees C for 300 milliseconds (plasma free hemoglobin, 116.3 +/- 34.7 mg%; p < 0.05). Lethal injury to neutrophils did not occur, even at exposure at 80 degrees C for 1,200 milliseconds. Sublethal injury to red blood cells did not occur until exposure at 60 degrees C for 1,200 milliseconds. Sublethal injury to neutrophils did not occur until exposure at 60 degrees C for 600 milliseconds (percent change in oxidative burst = 28.9 +/- 0.96%; p < 0.05).
The exposure of human red blood cells and neutrophils to temperatures up to 60 degrees C for up to 600 milliseconds does not cause lethal or sublethal injury. These findings contribute to the body of evidence supporting the use of centrally infused IVF at temperatures greater than 40 degrees C for active core rewarming.
Individuals at extremes of age and those who have certain underlying medical conditions are at greatest risk for hypothermia. Hypothermia may occur during any season of the year and in any climate. Prompt recognition of hypothermia and early institution of the rewarming techniques are imperative for a successful outcome with minimal complications. Several rewarming techniques are available and the decision to use any of them depends on the degree of hypothermia, the condition of the patient, and the rewarming rate possible with the technique chosen.
Hypothermia occurs commonly in severely injured patients and is associated with a high mortality rate. It perturbs the normal homeostatic response to injury and affects multiple organ systems and physiologic processes. In trauma patients, hypothermia-induced coagulopathy often leads to marked bleeding diathesis and frequently provides a challenge for the surgeon. Once hypothermia occurs, it is often difficult to correct. Efforts to prevent and treat hypothermia in trauma patients should be instituted in the field and continued as an integral part of the resuscitation process. Hospital personnel and physicians at various levels caring for trauma patients from the initial injury and thereafter should bear in mind that a patient's temperature is as important as any other vital sign. Appropriate measures for preventing and treating hypothermia should be instituted promptly and tended to with utmost vigilance.
Rewarming victims of hypothermia such as divers or immersion victims, participants in winter sports and military operations, and surgical patients on cardiopulmonary bypass (CPB) may lead to vascular instability, multiorgan failure, shock, and even death. While the causes of these rewarming symptoms are unknown, they may be related to bacterial lipopolysaccharide (LPS) translocated from the intestines into the circulation due to splanchnic ischemia. We have determined LPS during the cooling (to 31.5 degrees-34.0 degrees C) and rewarming phases of hypothermic surgery in 11 patients at the Stanford University Medical Center. During rewarming, there was an LPS spike in 6/11, in one more patient there was an LPS spike during surgery but not during rewarming, and in 4/11 there was no rise in LPS, i.e., a temporary endotoxemia occurred in 7/11 (63.6%) patients, usually at the commencement of rewarming. All four patients with no LPS spike received dexamethasone for at least 7 days before surgery. We propose that hypothermia reduced splanchnic blood flow (BF), causing ischemic damage to the gut wall and translocation of LPS from the gut into the vascular space. Upon rewarming, splanchnic BF is restored, the translocated LPS transits from the splanchnic to the systemic circulations as a bolus, and the gut wall is healed. No sequelae occurred in these patients because of their adequately functioning immune systems. However, had they been immunocompromised, symptoms might have occurred. Rewarming of accident victims probably also incurs a similar risk of endotoxemia, and dexamethasone may have protected the gut wall. Further studies are indicated.
To show that resuscitation from hypothermic, hemorrhagic shock using 65 degrees C intravenous fluid results in a more rapid return to euthermia compared with 40 degrees C intravenous fluid, without significant endothelial or hemolytic injury.
Fourteen anesthetized beagles (10-12 kg) were cooled to a core temperature of 30 degrees C and hemorrhaged to a mean arterial pressure of 40 to 45 mm Hg for 30 minutes. The animals were randomized to receive either 65 degrees C or 40 degrees C intravenous fluid through a specially designed catheter at a rate of 80% of their blood volume per hour until euthermic (37 degrees C) or for 2 hours.
Blood pressure, pulmonary artery pressure, heart rate, and core temperature were continuously monitored. Blood samples were collected at baseline, after hemorrhage, 2 hours of resuscitation, and at postmortem examination after 7 days of survival. Laboratory measurements included complete blood count, plasma-free hemoglobin, and osmotic fragility. Values were compared using the Student's paired or unpaired t test with p approximately 0.05 indicating significance. Postmortem examination included light microscopy of the proximal superior vena cava or right atrium.
Animals receiving 65 degrees C intravenous fluid warmed 3.6 degrees C/hour, significantly faster than the 40 degrees C animals (1.9 degrees C/hour). There were no significant differences in plasma-free hemoglobin or osmotic fragility. Endothelial injuries were found in two animals in each group. These defects occurred along the path of catheter insertion and not at the infusion site.
Central intravenous fluid at 65 degrees C is a more rapid means of treating hypothermia than standard 40 degrees C intravenous fluid. It is safe even in hypovolemic animals.
This paper reviews literature on the topic of cold stress, near-drowning and hypothermia, written mainly since the last review of this type in this journal. The main effects of cold stress, especially in cold water immersion, include the "cold shock" response, local cooling causing decrements in physical and mental performance, and ultimately core cooling as hypothermia occurs. The section on cold-water submersion (near-drowning) includes discussion regarding the various mechanisms for brain and body cooling during submersion. The mechanisms for cold-induced protection of the anoxic brain are discussed with attention given to decreased brain temperature and the Q10 principle, the mammalian dive reflex and a newly considered mechanism; cold-induced changes in neurotransmitter release (i.e., glutamate and dopamine). The section on the post-cooling period includes the post-rescue collapse and subsequent rewarming strategies used in the field, during emergency transport or in medical facilities. Recent research on topics such as inhalation warming, body-to-body warming, radio wave therapy, warm water immersion, exercise, body cavity lavage, and cardiopulmonary bypass is reviewed. Information on new methods of warming, including arteriovenous anastomoses (AVA) warming (by application of heat- with or without negative pressure application-to distal extremities in an effort to increase AVA blood flow), forced-air warming, and peripheral vascular extracorporeal warming, are discussed.
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Even mild hypothermia provides marked protection against cerebral ischemia in animal models. Hypothermia may be of therapeutic value during neurosurgical procedures. However, current cooling systems often fail to induce sufficient hypothermia before the dura is opened. Furthermore, they usually fail to restore normothermia by the end of surgery, thus delaying extubation. We evaluated a new internal heat-exchanging catheter. Eight ASA physical status II-IV patients (29-72 yr) undergoing craniotomy were enrolled. After the induction of general anesthesia, we introduced the SetPoint catheter into the inferior vena cava via a femoral vein. The target core body temperature was 34 degrees C-34.5 degrees C. After reaching the target, core temperature was maintained until the dura was closed. Target core temperature was then set to 37.0 degrees C, and the patient was rewarmed as quickly as possible. Seven patients had a tumor resection, and one had an aneurysm clipped. The core-cooling rate was 3.9 degrees C +/- 1.6 degrees C/h, and the rewarming rate was 2.0 degrees C +/- 0.5 degrees C/h; core temperature was 35.9 degrees C +/- 0.2 degrees C by the end of surgery. Patients were subsequently kept normothermic for 3 h before the catheter was removed. No thrombus or other particulate material was identified on the extracted catheters. None of the patients suffered any complications that could be attributed to the SetPoint system or thermal management.
Implications:
Because current systems for inducing therapeutic hypothermia are too slow, we tested an internal counter-current thermal management system during hypothermic neurosurgery. The SetPoint catheter cooled at 3.9 degrees C +/- 1.6 degrees C/h and rewarmed at 2.0 degrees C +/- 0.5 degrees C/h. Catheter-based internal thermal management thus seems to be rapid and effective.
Infusion of cold fluids in a patient leads to a reduction of core temperature and subsequently worsens hypothermia. We evaluated the efficacy of a newly developed self-warming insulation device for use in pre-hospital rescue.
We studied 50 trauma patients with a rescue time of more than one hour. They were randomly assigned to either infusions taken directly from a warming box in the ambulance (Group A, n = 25) or infusions taken from the warming box and packed in an insulation device (Group B, n = 25). We recorded ambient temperatures, infusion temperatures in five-minute-steps and transport duration of the infusions from the ambulance to the site of accident.
Ambient temperatures and transport duration did not differ significantly between both groups. In Group A the infusion temperature decreased from 36.0 +/- 6.4 degrees C to 19.8 +/- 6.8 degrees C during the transport from the ambulance to the site of accident. In Group B infusion temperature decreased only about 1 degree C. In Group A the temperature of the infusion continued to decrease until the end of measurements. In contrast in Group B the infusion temperature even increased by 0.5 degree C over the measurement period. These differences between the two groups were statistically significant.
Our data show that even pre-warmed infusions from a warming box cool down considerably before they can be given to the patient. A self-warming insulation device can stabilize infusion temperature even under extreme conditions of prehospital trauma care.
Hypothermia is a common finding in severely injured patients. Historically described as a consequence of wartime casualties where cold exposure was common, this topic has resurfaced in the trauma literature because of the increasing recognition of the morbidity and mortality associated with hypothermia. Hypothermia, along with acidosis and coagulopathy, has been identified as a component of the "lethal triad" in injured patients, and has been shown to contribute to increased mortality in these patients. Decreases in core temperature during the course of initial evaluation and resuscitation are common, and can contribute to poor outcomes in the injured patient. As induced hypothermia has been shown to be beneficial in some clinical situations, recent animal studies have attempted to investigate whether hypothermia in the trauma patient has any beneficial effects. This review examines the incidence and pathophysiology of hypothermia, and discusses mechanisms of heat loss and rewarming techniques that can be utilized in the trauma patient.
Accidental hypothermia is defined as an unintentional decrease in core body temperature to below 35 degrees C. Hypothermia causes hundreds of deaths in the United States annually. Victims of accidental hypothermia present year-round and in all climates with a potentially confusing array of signs and symptoms, but increasing severity of hypothermia produces a predictable pattern of systemic organ dysfunction and associated clinical manifestations. The management of hypothermic patients differs in several important respects from that of euthermic patients, so advance knowledge about hypothermia is prerequisite to optimal management. The paucity of randomized clinical trials with hypothermic patients precludes creation of evidence-based treatment guidelines, but a clinically sound management strategy, tailored to individual patient characteristics and institutional expertise and resources, can nonetheless be gleaned from the literature. This article reviews the epidemiology, pathophysiology, clinical presentation, and treatment of accidental hypothermia. Initial evaluation and stabilization, selection of a rewarming strategy, and criteria for withholding or withdrawing support are discussed.
Purpose:
Many victims of accidental hypothermia are successfully resuscitated, but questions remain regarding the optimum rewarming techniques. Most of the invasive warming techniques such as closed thoracic lavage, hemodialysis, peritoneal dialysis, and cardiopulmonary bypass require specialized personnel, equipment, and procedures that are not readily available in all facilities. The objective of this study was to investigate the technical feasibility of utilizing a novel veno-veno rewarming circuit to resuscitate severely hypothermic subjects. If this alternative invasive warming technique is successful, it could be available to treat hypothermic patients in virtually any emergency department setting.
Methods:
The rewarming system consisted of a Baxter ThermaCyl warmer (Baxter Co., McGaw Park, IL), a roller pump, hemodialysis tubing, connectors, and 2 venous catheters. Blood was pumped from the body via the femoral vein, through the roller pump, into the warmer, and then returned to the body via the right jugular vein. Seven adult mongrel hounds of similar weights (20 to 25 kg) were anesthetized and instrumented for data collection. Temperature probes were placed in the rectum, the peritoneal cavity, and the esophagus to record core temperatures. Each animal was cooled by ice packing to a central core temperature of 29 degrees C and then rewarmed using the described veno-veno circuit. Vital signs, pulse oximetry, cardiac rhythm, and laboratory values were obtained prior to cooling the animals, and were repeated for every degree Celsius change once warming began. Christopher Haughn, MD, was the second place winner in the Basic Sciences Resident Competition at the Ohio American College of Surgeons meeting.
Results:
Because of technical difficulties, data from 1 dog were not included in the results. Of the remaining 6 dogs, all were rewarmed from 29 degrees C to 37 degrees C. Adverse side effects included gross hematuria, acidemia (median pH decrease was 0.088), and decreases in haptoglobin (median decrease 13.5 g/dl), hemoglobin (median decrease 1.35 g/dl), and arterial pO(2) level (median decrease 167 mm Hg). Decreases in blood pressure and heart rate were also noted during the cooling process, but reversed upon rewarming.
Conclusions:
From this pilot study, we conclude that our novel veno-veno circuit rewarming is a feasible method of rewarming hypothermic subjects and warrants further investigation and comparison with other active warming methods.
Numerous studies support the use of warmed intravenous fluids in hypothermic patients. The most effective method to accomplish this goal in a cold prehospital, wilderness, or combat setting is unknown. We evaluated various methods of warming intravenous fluids for a bolus infusion in a cold remote environment.
One liter and 500 mL bags of intravenous fluid at 5 degrees C were heated using various methods in a 5 degrees C cold room. Methods included attachment of 3 types of chemical heat packs and heating the fluid in a pot on a camping stove. For all methods, fluids were run at a wide-open rate through an intravenous line with an 18-gauge catheter attached to the end to simulate a bolus infusion. The temperature of the fluid at the end of the intravenous line was measured. Each method was tested twice. Equipment weight and setup times are reported. Mean infusion temperatures for the various methods are compared.
Equipment weights ranged from 19 to 665 gm. Setup times ranged from 5 to 11 minutes. The 2 methods which achieved the desired mean infusion temperature of 35 to 42 degrees C without excessive maximum temperatures were 1) 2 Meal Ready to Eat hot packs attached to a 500 mL bag of fluid for 10 minutes prior to infusion, and 2) a camping stove heating the surface of a 500 mL bag of fluid to 75 degrees C prior to infusion. Other methods, including the use of commonly available heat packs and a commercially available IV fluid warmer were ineffective, with mean infusion temperatures ranging from 7 to 12 degrees C.
Heating of cold intravenous fluids in a cold environment is possible using either Meal Ready to Eat heat packs or a camping stove. Further study is needed to evaluate the ability of either method to consistently produce an appropriate fluid temperature given various ambient and initial fluid temperatures.
In hot climates, only high temperature fluids (are greater than 100 F) may be available for treatment of blood loss shock in combat casualties. Can the hot fluid be used safely and effectively? We compared hot Ringer's lactate (51.7% C/125 F) resuscitation (n=10) to body-temperature (100 F) fluid resuscitation (n=10) in a hemorrhagic shock dog model. One liter of 125 F fluid, as part of the resuscitation, did not cause hyperthermia, red blood cell hemolysis, or any significantly different response in the cardiovascular system when compared to body-temperature fluid. All animals in both groups survived. These findings suggest that battlefield use of hot fluids in controlled amounts can be safe and effective for treatment of blood loss shock in human combat casualties.
To evaluate the consequences of clinical hypothermia associated with sepsis syndrome and septic shock.
Analysis of data from a multi-institutional, randomized, placebo-controlled, prospective study with predetermined end-point analysis of development of shock, recovery from shock, hospital length of stay, and death.
Multi-institutional medical and surgical ICUs.
Patients meeting predetermined criteria for severe sepsis syndrome.
Appropriate sepsis and shock care with 50% of patients receiving methylprednisolone and 50% receiving placebo.
The occurrence rate of hypothermia (< 35.5 degrees C) is 9% in this population. When compared with febrile patients, hypothermic patients had a higher frequency of central nervous system dysfunction (88% vs. 60%), increased serum bilirubin concentration (35% vs. 15%), prolonged prothrombin times (50% vs. 23%), shock (94% vs. 61%), failure to recover from shock (66% vs. 26%), and death (62% vs. 26%). The hypothermic patients were also more likely to be classified as having a rapidly or ultimately fatal disease upon study admission.
This prospective study confirms that hypothermia associated with sepsis syndrome has a significant relationship to outcome manifest by increased frequency of shock and death from shock. This finding is in sharp contrast to the protective effects of induced hypothermia in septic animals and perhaps man.
Hypothermia retards cardiac contraction and prolongs the subphases of the cardiac cycle in varying degrees. Six anaesthetized beagle dogs were catheterized and cooled between ice bags until the aortic blood temperature was 25 degrees C and then rewarmed to normothermia. The speed of relaxation decreased to a half from its value in normothermia as indicated by the time constant of exponential isovolumic ventricular pressure fall and by the change in the negative dp/dt. It is suggested that retardation of relaxation is connected with temperature dependent changes in calcium kinetics. Decrease of cardiac output was mediated mainly by decreased stroke volume indicating sympathetic tone in spite of cold narcosis.
There is a lack of detailed knowledge of the pathophysiologic mechanisms initiated during and after rewarming. To study cardiac function after rewarming from hypothermia sodium pentobarbital anesthetized open chest-dogs were cooled to 25 degrees C and rewarmed. Myocardial blood flow was measured at different temperatures, and blood samples were drawn from the aorta and the coronary sinus for metabolic measurements. Mean aortic blood pressure (AOP) and aortic blood flow were recorded. Compared to precooling, AOP and heart rate were both significantly reduced during hypothermia. During rewarming stroke volume (SV) decreased significantly. At the end of rewarming AOP and SV were significantly lower than before cooling and myocardial blood flow, as well as oxygen and lactate uptake were only 50% of precooling levels. The present study demonstrated that hypothermia and rewarming depress cardiovascular function. Changes in peripheral vascular function, myocardial metabolism and contractility, may lead to the observed reduction in recovery upon rewarming.
Hypothermia is a major problem in patients who have sustained trauma. We reviewed the cases of 100 consecutive trauma patients transferred directly to the operating room (OR) from the Emergency Department (ED) in a Level I trauma center; 26 cases could not be evaluated. Forty-two patients (57%) became hypothermic at some time between injury and leaving the OR. Fifty-five patients (74%) had a temperature (T) recorded on arrival to the ED; but only 7 (12%) were hypothermic (34.7 degrees +/- 1.5 degrees C). In contrast, 34 patients (46%) arrived in the OR hypothermic (34.8 degrees +/- 0.9 degrees C) and 26 (76%) of these left the OR hypothermic (34.8 degrees +/- 0.9 degrees C). Eight additional patients (20%) arriving in the OR with a T greater than 35.9 degrees C left the OR hypothermic (35.1 degrees +/- 0.4 degrees C). The mean T loss in the ED was significantly greater than that lost in the OR (-0.8 degrees +/- 0.7 degrees C vs. 0.0 degrees +/- 0.6 degrees C; p less than 0.0001, ANOVA). Ninety-two percent of the patients lost temperature in the ED, while 43% of the patients gained temperature in the OR. Hypothermia was associated with lower Trauma Scores, and those patients who were severely hypothermic received more intravenous fluids. However, the impact of fluid infusion was not independent from Trauma Score and did not fully explain the magnitude of the heat loss. These data suggest that hypothermia in trauma patients has a multifactoral etiology related to the magnitude of injury and that the major T loss occurs in the ED rather than in the OR.(ABSTRACT TRUNCATED AT 250 WORDS)
Hypothermia is common after severe injury, and has been associated with an increased mortality rate in patients stratified by anatomic indices of injury severity. In this retrospective study of 173 patients, early post-traumatic hypothermia was found to correlate with physiologic indicators of volume deficit, independently of the amount of intravenous fluid received. There was no correlation found between admission core temperature and time from injury, blood alcohol, or presence of severe closed head injury. Hypothermic patients (less than 35 degrees C) had a lower predicted probability of survival and a higher mortality rate than euthermic patients (greater than or equal to 35 degrees C). However, when patients were stratified by physiologic and anatomic indicators of injury severity, mortality rates among the euthermic and hypothermic patients were not significantly different. Early post-traumatic hypothermia does not appear to exert an independent effect upon outcome.
Hypothermia is defined and classified, and the physiology of temperature regulation summarized; fluid balance and the phenomenon of symptomless cooling are considered in more detail. The symptoms and signs of hypothermia are charted, with cautions, and the problems considered of making any diagnosis, including that of death, in hypothermic patients. Recommendations for treatment are complicated by the possible presence of other factors including drowning and the so-called 'diving reflex' phenomenon. There are many methods of rewarming and all are safe if used with intensive care monitoring. However, for field use by the rescue services there are only three practical methods. The traditional explanation of why survivors die after rescue is discarded with an alternative proposed. Since hypothermia is not numerically the most important cause of cold-related deaths, the other dangers are considered. Finally caution is advised when interpreting published papers on hypothermia.
Baboons that were subjected to systemic hypothermia at 32 C had an arm skin temperature of 27.3 C and bleeding time of 5.8 minutes. With local warming of the arm skin to 34 C, the bleeding time was 2.4 minutes. In normothermic baboons with arm skin temperature of 34.6 C, the bleeding time was 3.1 minutes. Local cooling of the arm skin to 27.6 C produced a bleeding time of 6.9 minutes. Increasing the skin temperature of the arm in hypothermic baboons to 38.9 C and in normothermic baboons to 40.1 C reduced bleeding times to 2.1 and 2.3 minutes, respectively. In both hypothermic and normothermic baboons there was a negative and significant correlation between the bleeding time and the arm skin temperature and the thromboxane B2 level in the shed blood obtained at the template bleeding time site. There was a significant positive correlation between the thromboxane B2 level in the shed blood and the arm skin temperature. Both in-vivo and in-vitro studies have shown that the production of thromboxane B2 by platelets is temperature-dependent, and that a cooling of skin temperature produces a reversible platelet dysfunction. Data also suggest that when a hypothermic patient bleeds without surgical cause, skin and wound temperature should be restored to normal before the administration of blood products that are not only expensive but may also transmit disease.
Warming plastic bags containing intravenous solutions in a microwave oven (MWO) raised the temperature from 18 degrees C to an average of 34.1 degrees, 40.2 degrees, and 42.8 degrees C when treated for 120, 150, and 160 seconds, respectively. Fluids at 18 degrees C, when passed through a blood warmer, resulted in temperatures at the distal end (DE) of about 27 degrees C; but if the bags were priorly warmed to 42 degrees C, fluids arrived at the DE at a temperature of about 30 degrees C. Fluids heated by MWO to 42 degrees C through a single short tubing 180 cm long arrived at the DE at a temperature of 33.7 degrees C. Fluids administered at operating room ambient temperature of 18 degrees C arrived to the DE with a temperature of about 19 degrees C, thus most likely contributing to lowering the body temperature of traumatized patients treated with large volumes given at rapid flows. One group of 19 patients undergoing repair of injuries to extremities received infusions warmed by MWO to 42 degrees, while other groups received them at about 20 degrees. After an initial fall, average temperature in the former tended toward normal levels while in the latter, body temperature declined. The simple expedience of MWO warming of the bags to 42 degrees C, and flowing through shorter administration tubing, appears to ameliorate this complication and in some cases prevents it.
The effect of intraoperative and postoperative temperature on morbidity, mortality, and other clinical risk factors was evaluated in 100 consecutive general surgical patients admitted postoperatively to a surgical intensive care unit. Hypothermia (temperature less than 97 degrees F) was present in 77 percent of the patients intraoperatively, in 53 percent at the end of surgery, and in 21 percent at 4 hours. Mortality was increased with patient age greater than 55 years, emergency surgery, operative blood pressure less than 100 mm Hg, operative fluid requirements greater than 1,500 ml/hour, temperature less than 97 degrees F at 2, 4, and 8 hours postoperatively, and presence of postoperative complications. Intraoperative fluid requirements were significantly greater for patients with mortality risk factors. Patients over 55 years of age were more often hypotensive and hypothermic than younger patients, but mortality was increased only for patients less than 55 years of age with a temperature of less than 97 degrees F at 8 hours or an operative blood pressure of less than 100 mm Hg. Mortality after general surgical procedures is increased with operative hypotensive and prolonged postoperative hypothermia. Hypothermic patients with mortality risk factors should be aggressively rewarmed postoperatively.