Article

Effects of Ambient Temperature and Forced-air Warming on Intraoperative Core Temperature: A Factorial Randomized Trial

January 2018
Anesthesiology 128(5):1

January 2018
128(5):1

DOI:10.1097/ALN.0000000000002099

Authors:

Background: The effect of ambient temperature, with and without active warming, on intraoperative core temperature remains poorly characterized. The authors determined the effect of ambient temperature on core temperature changes with and without forced-air warming. Methods: In this unblinded three-by-two factorial trial, 292 adults were randomized to ambient temperatures 19°, 21°, or 23°C, and to passive insulation or forced-air warming. The primary outcome was core temperature change between 1 and 3 h after induction. Linear mixed-effects models assessed the effects of ambient temperature, warming method, and their interaction. Results: A 1°C increase in ambient temperature attenuated the negative slope of core temperature change 1 to 3 h after anesthesia induction by 0.03 (98.3% CI, 0.01 to 0.06) °Ccore/(h°Cambient) (P < 0.001), for patients who received passive insulation, but not for those warmed with forced-air (-0.01 [98.3% CI, -0.03 to 0.01] °Ccore/[h°Cambient]; P = 0.40). Final core temperature at the end of surgery increased 0.13°C (98.3% CI, 0.07 to 0.20; P < 0.01) per degree increase in ambient temperature with passive insulation, but was unaffected by ambient temperature during forced-air warming (0.02 [98.3% CI, -0.04 to 0.09] °Ccore/°Cambient; P = 0.40). After an average of 3.4 h of surgery, core temperature was 36.3° ± 0.5°C in each of the forced-air groups, and ranged from 35.6° to 36.1°C in passively insulated patients. Conclusions: Ambient intraoperative temperature has a negligible effect on core temperature when patients are warmed with forced air. The effect is larger when patients are passively insulated, but the magnitude remains small. Ambient temperature can thus be set to comfortable levels for staff in patients who are actively warmed.

Comparison of Early Effects of Perioperative Body Temperature Changes in Laparoscopic and Open Abdominal Surgery

Article

Jan 2021

The Heat Is On: Clinical Implications of Intraoperative Thermoregulation Research

Article

Mar 2018

David A Story

Incidence and associated factors of perioperative hypothermia in adult patients at a university-based, tertiary care hospital in Thailand

Article

Full-text available

Apr 2023
BMC Anesthesiol

Abstract Background Inadvertent perioperative hypothermia is an unintentional drop in core body temperature to less than 36 °C perioperatively and is associated with many negative outcomes such as infection, a prolonged stay in a recovery room, and decreased patient comfort. Objective To determine the incidence of postoperative hypothermia and to identify the associated factors with postoperative hypothermia in patients undergoing head, neck, breast, general, urology, and vascular surgery. The incidences of pre- and intraoperative hypothermia were examined as the intermediate outcomes. Materials and methods A retrospective chart review was conducted in adult patients undergoing surgery at a university hospital in a developing country for two months (October to November 2019). Temperatures below 36 °C were defined as hypothermia. Univariate and multivariate analyses were used to identify factors associated with postoperative hypothermia. Results A total of 742 patients were analyzed, the incidence of postoperative hypothermia was 11.9% (95% CI 9.7%-14.3%), and preoperative hypothermia was 0.4% (95% CI 0.08%-1.2%). Of the 117 patients with intraoperative core temperature monitoring, the incidence of intraoperative hypothermia was 73.5% (95% CI 58.8–90.8%), and hypothermia occurred most commonly after anesthesia induction. Associated factors of postoperative hypothermia were ASA physical status III-IV (OR = 1.78, 95%CI 1.08–2.93, p = 0.023) and preoperative hypothermia (OR = 17.99, 95%CI = 1.57-206.89, p = 0.020). Patients with postoperative hypothermia had a significantly longer stay in the PACU (100 min vs. 90 min, p = 0.047) and a lower temperature when discharged from PACU (36.2 °C vs. 36.5 °C, p

Incidence and Risk factors for Intraoperative Hypothermia during Cancer Surgery of Gastrointestinal Tracts: a single-center retrospective study

Preprint

Full-text available

Sep 2022

BACKGROUND Intraoperative hypothermia in cancer surgery of gastrointestinal tracts causes complications, but its related risk factors have been are not fully understood. The aim of study is to investigate the incidence and related risk factors. METHODS We retrospectively reviewed the medical records of 1217 patients aged from 18 to 85 years who underwent gastrointestinal tracts cancer surgery under general anesthesia in the gastrointestinal surgery department of the First Affiliated Hospital of Air Force Military Medical University from January through December, 2019. Incidences were calculated and associated risk factors were evaluated by univariate logistic regression and multivariate regression analyses. RESULTS The overall incidence of intraoperative hypothermia was 25.7%. The risk factors including that age<60yrs (OR, 0.658; 95% CI, 0.486 to 0.889), BMI≥22（kg/m2）(OR, 0.502; 95% CI, 0.367 to 0.687), Open abdominal surgery (OR, 0.480; 95% CI, 0.333 to 0.691), perioperative temperature≥37(℃) (OR, 0.160; 95% CI, 0.079 to 0.323), without warming mattress (OR, 0.402; 95% CI, 0.293 to 0.550). CONCLUSION The incidence of perioperative hypothermia was common while active warming during operation is low. We highlight that more attention needs to be paid on prevention of intraoperative hypothermia.

Incidence of postoperative hypothermia and its risk factors in adults undergoing orthopedic surgery under brachial plexus block: A retrospective cohort study

Article

Full-text available

Mar 2021
Int J Med Sci

Postoperative hypothermia increases patient mortality and morbidity. However, the incidence of, and risk factors for, postoperative hypothermia in patients undergoing surgery under brachial plexus block (BPB) as the primary method of anesthesia remain unclear. This study aimed to determine the incidence of, and risk factors for, postoperative hypothermia in patients undergoing surgery under BPB. We retrospectively analyzed 660 patients aged ≥ 19 years who underwent orthopedic surgery under BPB in our hospital between October 2014 and October 2019. Postoperative hypothermia was defined as a tympanic membrane temperature < 36 °C when the patient arrived in the post-anesthesia care unit. Multivariate logistic regression analysis was performed to identify the independent risk factors for postoperative hypothermia. Postoperative hypothermia was observed in 40.6% (268/660) of patients. Independent risk factors for postoperative hypothermia were lower baseline core temperature before anesthesia (odds ratio [OR] 0.355; 95% confidence interval [CI] 0.185-0.682), alcohol abuse (OR 2.658; 95% CI 1.105-6.398), arthroscopic shoulder surgery (OR 2.007; 95% CI 1.428-2.820), use of fentanyl (OR 1.486; 95% CI 1.059-2.087), combined use of midazolam and dexmedetomidine (OR 1.816; 95% CI 1.268-2.599), a larger volume of intravenous fluid (OR 1.001; 95% CI 1.000-1.002), and longer duration of surgery (OR 1.010; 95% CI 1.004-1.017). Postoperative hypothermia is common in adult patients undergoing orthopedic surgery under BPB. The risk factors identified in this study should be considered to avoid postoperative hypothermia in these patients.

Effect of forced-air warming by an underbody blanket on end-of-surgery hypothermia: A propensity score-matched analysis of 5063 patients

Article

Full-text available

Apr 2019
BMC Anesthesiol

Background: Underbody blankets have recently been launched and are used by anesthesiologists for surgical patients. However, the forced-air warming effect of underbody blankets is still controversial. The aim of this study was to determine the effect of forced-air warming by an underbody blanket on body temperature in anesthetized patients. Methods: We retrospectively analyzed 5063 surgical patients. We used propensity score matching to reduce the bias caused by a lack of randomization. After propensity score matching, the change in body temperature from before to after surgery was compared between patients who used underbody blankets (Under group) and those who used other types of warming blankets (Control group). The incidence of hypothermia (i.e., body temperature < 36.0 °C at the end of surgery) was compared between the two groups. A p value < 0.05 was considered to indicate statistical significance. Results: We obtained 489 propensity score-matched pairs of patients from the two groups, of whom 33 and 63 had hypothermia in the Under and Control groups, respectively (odds ratio: 0.49, 95% confidence interval: 0.31-0.76, p = 0.0013). Conclusions: The present study suggests that the underbody blanket may help reduce the incidence of intraoperative hypothermia and may be more efficient in warming anesthetized patients compared with other types of warming blankets. Trial registration: UMIN Clinical Trials Registry (Identifier: UMIN000022909 ; retrospectively registered on June 27, 2016).

Clinical Efficacy of 10 Min of Active Prewarming for Preserving Patient Body Temperature during Percutaneous Nephrolithotomy: A Prospective Randomized Controlled Trial

Article

Full-text available

Mar 2024

Background: Percutaneous nephrolithotomy (PNL) poses a risk of hypothermia. Additionally, general anesthesia lowers the thresholds for shivering and vasoconstriction, which leads to dysfunction of central thermoregulation. Perioperative hypothermia is associated with adverse outcomes after surgery. In this study, we aimed to demonstrate that prewarming for 10 min can effectively prevent early hypothermia during PNL. Methods: A total of 68 patients scheduled for elective PNL were recruited to this study from January to June 2022, but two patients were excluded because of a change in the surgical plan. After randomization, patients in the prewarming group (n = 32) received warming using a forced-air warming device for 10 min in the preoperative area before being transferred to the operating room, while the controls (n = 34) did not. The incidence of hypothermia within the first hour after inducing general anesthesia was the primary outcome. Perioperative body temperatures and postoperative recovery findings were also evaluated. Results: Early intraoperative hypothermia decreased significantly more in the prewarming group than in the control group (9.4% vs. 41.2%, p = 0.003). Moreover, the net decrease in core body temperature during surgery was smaller in the prewarming group than in the control group (0.2 °C, vs. 0.5 °C, p = 0.003). In addition, the prewarmed patients had a lower incidence of postoperative shivering and a shorter post-anesthesia-care unit (PACU) stay (12.5% vs. 35.3%, p = 0.031; and 46 vs. 50 min, p = 0.038, respectively). Conclusions: Prewarming for 10 min decreased early hypothermia, preserved intraoperative body temperature, and improved postoperative recovery in the PACU.

Effect of prewarmimg on body temperature and shivering in total knee arthroplasty patients after surgery

Article

Jul 2021

Ratchanee Sukanthachalathon

Analysis of hospital and payer costs of care: aggressive warming versus routine warming in abdominal major surgery

Article

Full-text available

Nov 2023

Background Hypothermia is common and active warming is recommended in major surgery. The potential effect on hospitals and payer costs of aggressive warming to a core temperature target of 37°C is poorly understood. Methods In this sub-analysis of the PROTECT trial (clinicaltrials.gov, NCT03111875), we included patients who underwent radical procedures of colorectal cancer and were randomly assigned to aggressive warming or routine warming. Perioperative outcomes, operation room (OR) scheduling process, internal cost accounting data from the China Statistical yearbook (2022), and price lists of medical and health institutions in Beijing were examined. A discrete event simulation (DES) model was established to compare OR efficiency using aggressive warming or routine warming in 3 months. We report base-case net costs and sensitivity analyses of intraoperative aggressive warming compared with routine warming. Costs were calculated in 2022 using US dollars (USD). Results Data from 309 patients were analyzed. The aggressive warming group comprised 161 patients and the routine warming group comprised 148 patients. Compared to routine warming, there were no differences in the incidence of postoperative complications and total hospitalization costs of patients with aggressive warming. The potential benefit of aggressive warming was in the reduced extubation time (7.96 ± 4.33 min vs. 10.33 ± 5.87 min, p < 0.001), lower incidence of prolonged extubation (5.6% vs. 13.9%, p = 0.017), and decreased staff costs. In the DES model, there is no add-on or cancelation of operations performed within 3 months. The net hospital costs related to aggressive warming were higher than those related to routine warming in one operation (138.11 USD vs. 72.34 USD). Aggressive warming will have an economic benefit when the OR staff cost is higher than 2.37 USD/min/person, or the cost of disposable forced-air warming (FAW) is less than 12.88 USD/piece. Conclusion Despite improving OR efficiency, the economic benefits of aggressive warming are influenced by staff costs and the cost of FAW, which vary from different regions and countries. Clinical trial registration clinicaltrials.gov, identifier (NCT03111875).

Effect of active warming on perioperative cardiovascular outcomes: a systematic review and meta-analysis of randomized controlled trials

Article

Full-text available

Jun 2023

Purpose The objective of this study was to provide an updated review on the active warming effects on major adverse cardiac events, 30-day all-cause mortality, and myocardial injury after noncardiac surgery. Method We systematically searched MEDLINE, EMBASE, CINAHL, Cochrane CENTRAL, Web of Science, and Chinese BioMedical Literature Database. We included randomized controlled trials of adult population undergoing noncardiac surgeries that concentrate on the comparison of active warming methods and passive thermal management. Cochrane Collaboration’s tool was applied for risk-of-bias assessment. We used trial sequential analysis to evaluate the possibility of false positive or negative results. Results A total of 13,316 unique records were identified, of which only 19 with reported perioperative cardiovascular outcomes were included in the systematic review and nine of them were included in final meta-analysis. No statistically significant difference between active warming methods and routine care was found in major adverse cardiac events (RR 0.56, 95% confidence interval (CI) 0.14–2.21, I ² = 71%, number of events 59 vs. 70), 30-day all-cause mortality (RR 0.81, 95% CI 0.43–1.54, I ² = 0%, number of events 17 vs. 21), and myocardial injury after noncardiac surgery (RR 0.61, 95% CI 0.17–2.22, I ² = 79%, number of events 236 vs. 234). Trial sequential analysis suggests that current trials did not reach the minimum information size regarding the major cardiovascular events. Conclusions Compared to routine perioperative care, we found that active warming methods are not necessary for cardiovascular prevention in patients undergoing noncardiac surgery.

Hypothermia is an independent risk factor for prolonged ICU stay in coronary artery bypass surgery: an observational study

Article

Full-text available

Mar 2023

Maintenance of normothermia is a critical perioperative issue. The warming process after hypothermia tends to increase oxygen demand, which may lead to myocardial ischemia. This study explored whether hypothermia was an independent risk factor for increased morbidity and mortality in patients receiving CABG. We conducted a retrospective observational study of CABG surgeries performed from January 2018 to June 2019. The outcomes of interest were mortality, surgical site infection rate, ventilator dependent time, intensive care unit (ICU) stay, and hospitalization duration. Data from 206 patients were analysed. Hypothermic patients were taller (p = 0.012), had lower left ventricular ejection fraction (p = 0.016), and had off-pump CABG more frequently (p = 0.04). Our analysis noted no incidence of mortality within 30 days. Hypothermia was not associated with higher surgical site infection rate or longer intubation time. After adjusting for sex, age, cardiopulmonary bypass duration, left ventricular ejection fraction, and EuroSCORE II, higher EuroSCORE II (p < 0.001; odds ratio 1.2) and hypothermia upon ICU admission (p = 0.04; odds ratio 3.8) were independent risk factors for prolonged ICU stay. In addition to EuroSCORE II, hypothermia upon ICU admission was an independent risk factor for prolonged ICU stay in patients receiving elective CABG.

Construction and validation of postoperative hypothermia prediction model for patients undergoing joint replacement surgery

Article

Full-text available

Aug 2022

Aim: To construct and validate a postoperative hypothermia prediction model for patients undergoing joint replacement surgery. Background: Postoperative hypothermia is one of the harmful perioperative complications in patients undergoing joint replacement surgery. The previous studies mainly focused on intraoperative hypothermia prediction models. The prediction model for postoperative hypothermia in patients with joint replacement surgery was understudied. Design: Cohort study. Methods: We collected data from 503 participants undergoing joint replacement surgery in a tertiary hospital from January 2019 to December 2021. Of those, 404 cases were assigned to the modelling and 99 to the validation groups. Logistic regression was used to construct the model. The AUC was used to test the predictive effect of the model. Finally, 99 cases were used to verify the application effect of the model. A TRIPOD checklist was used to guide the reporting of this study. Results: The factors entered into the prediction model were age, intraoperative hypothermia, BMI, heat preservation measures and platelet (PLT). The model was constructed as follows: Logit (P) = .537 + 3.669 × 1 (intraoperative hypothermia) + .030 × age - .289 × BMI + 2.857 × 1 (intraoperative insulation measures) + .003 × PLT. Hosmer-Lemeshow test, p = .608, the area under the receiver operating characteristic curve (AUC) was .861. The Youden index was .530, the sensitivity was .599 and the specificity was .93. The incidence of postoperative hypothermia in the modelling group was 42.93% (173/404), and that in the verification group was 43.43% (43/99), χ2 = .012, p = .912. The correct practical application rate was 87.88%. This model has a good application effect. Conclusion: The current prediction model provided a reference for clinical screening of patients with high-risk hypothermia after joint replacement surgery. Relevance to clinical practice: Clinical nurses can use the developed prediction model to predict the occurrence of postoperative hypothermia and provide a reference for the preventive measure.

Risk Factors for Postoperative Hypothermia in Patients Undergoing Robot-Assisted Gynecological Surgery: A Retrospective Cohort Study

Article

Full-text available

Jun 2022
Int J Med Sci

Since postoperative hypothermia increases the morbidity and mortality rates of surgery, identifying its risk factors is an important part of perioperative management. Considering the increasing demand for robot-assisted surgery and other characteristics of conventional laparoscopic surgery, identifying the risk factors for hypothermia in robot-assisted surgery is necessary. However, this has not yet been clearly established. This study aimed to identify the risk factors and incidence rate of postoperative hypothermia in patients undergoing robot-assisted gynecological surgery. In total, 516 patients aged ≥ 19 years undergoing robot-assisted gynecological surgery at a single university hospital between January 2018 and November 2020 were retrospectively analyzed. Postoperative hypothermia was defined as 36.0°C or lower body temperature at the end of the surgery, and multivariate logistic regression analysis was performed to identify the risk factors for postoperative hypothermia. Among the 516 patients, the incidence rate of postoperative hypothermia was 28.1% in 145 patients. The independent risk factors for postoperative hypothermia included body mass index ≤ 22.9 kg/m2, baseline heart rate ≤ 73 rate/min, baseline body temperature ≤ 36.8°C, use of intraoperative nicardipine, and amount of administered intravenous fluid larger than 800 mL. Therefore, to prevent hypothermia in patients undergoing robot-assisted gynecological surgery, these risk factors must be considered.

Effect of active forced air warming during the first hour after anesthesia induction and intraoperation avoids hypothermia in elderly patients

Article

Full-text available

Feb 2022
BMC Anesthesiol

Background The study aimed at exploring an optimal temperature model of forced air warming during the first hour after induction and intraoperation to prevent hyperthermia for elderly patients undergoing laparoscopic abdominal surgery. Methods There were 218 patients that were randomly divided into 3 groups warmed with a forced-air warmer during surgery: Group L (intraoperative warming set to 38 °C, n = 63), Group H (intraoperative warming set to 42 °C, n = 65) and Group LH (intraoperative warming set to 42 °C for the first hour then set to 38 °C, n = 65). Core temperature in the preoperative room and PACU was measured by a tympanic membrane thermometer and in the operation room, a nasopharyngeal temperature probe was recorded. The rate of perioperative hypothermia, defined as a reduction in body temperature to < 36 °C was recorded as the primary outcome. Intraoperative anesthetic dosage, recovery time, adverse events, thermal comfort and satisfaction score were measured as secondary outcome. Results The incidence of intraoperative and postoperative hypothermia was significantly lower in Group LH and Group H than Group L (18.75 and 15.62% vs 44.44%, P<0.001; 4.69 and 4.69% vs 20.63%, P<.05). Anesthetic dosage of rocuronium was lower in Group L than other two groups, with the opposite result of recovery time. The number of patients with shivering was higher in Group L but sweating was higher in Group H. Both of the thermal comfort and satisfaction score was highest in Group LH. Conclusion A temperature pattern of forced air warming set at 42 °C during the first hour after anesthesia induction and maintained with 38 °C was a suitable choice for elderly patients undergoing laparoscopic abdominal surgery lasting for more than 120 min. Trial registration Chictr.org.cn ChiCTR-2,100,053,211.

Development and internal validation of an algorithm to predict intraoperative risk of inadvertent hypothermia based on preoperative data

Article

Full-text available

Nov 2021

Intraoperative hypothermia increases perioperative morbidity and identifying patients at risk preoperatively is challenging. The aim of this study was to develop and internally validate prediction models for intraoperative hypothermia occurring despite active warming and to implement the algorithm in an online risk estimation tool. The final dataset included 36,371 surgery cases between September 2013 and May 2019 at the Vienna General Hospital. The primary outcome was minimum temperature measured during surgery. Preoperative data, initial vital signs measured before induction of anesthesia, and known comorbidities recorded in the preanesthetic clinic (PAC) were available, and the final predictors were selected by forward selection and backward elimination. Three models with different levels of information were developed and their predictive performance for minimum temperature below 36 °C and 35.5 °C was assessed using discrimination and calibration. Moderate hypothermia (below 35.5 °C) was observed in 18.2% of cases. The algorithm to predict inadvertent intraoperative hypothermia performed well with concordance statistics of 0.71 (36 °C) and 0.70 (35.5 °C) for the model including data from the preanesthetic clinic. All models were well-calibrated for 36 °C and 35.5 °C. Finally, a web-based implementation of the algorithm was programmed to facilitate the calculation of the probabilistic prediction of a patient’s core temperature to fall below 35.5 °C during surgery. The results indicate that inadvertent intraoperative hypothermia still occurs frequently despite active warming. Additional thermoregulatory measures may be needed to increase the rate of perioperative normothermia. The developed prediction models can support clinical decision-makers in identifying the patients at risk for intraoperative hypothermia and help optimize allocation of additional thermoregulatory interventions.

Risk Stratification for Organ/Space Surgical Site Infection in Advanced Digestive System Cancer

Article

Full-text available

Nov 2021

Background Organ/space surgical site infection (organ/space SSI) is a serious postoperative complication, closely related to a poor prognosis. Few studies have attempted to stratify the risk of organ/space SSI for patients with advanced digestive system cancer. This study aimed to identify a simple risk stratification for these patients based on perioperative factors. Methods The study was based on two randomized controlled trials (RCT) (NCT02715076, ChiCTR-IPR-17011099), including 839 patients undergoing elective radical resection of advanced digestive system cancer. The primary outcome was organ/space SSI within 30 days after surgery. Multivariable logistic regression model was used to identify risk factors. The risk of organ/space SSI stratified over those risk factors was compared using chi-square tests and the relative risk (RR) was estimated. Results Among the 839 patients, 51 developed organ/space SSI (6.1%) within 30 days after surgery. According to the multivariable logistic regression model, 3 procedure types, including gastrectomy (OR=8.22, 95% CI: 2.71-24.87, P<0.001), colorectal resection (OR=8.65, 95% CI: 3.13-23.85, P<0.001) and pancreatoduodenectomy (OR=7.72, 95% CI: 2.95-20.21, P<0.001), as well as anaesthesia time > 4 h (OR=2.38, 95% CI: 1.08-5.27, P=0.032) and prolonged ICU stay (OR=4.10, 95% CI: 1.67-10.10, P=0.002), were risk factors for postoperative organ/space SSI. The number of risk factors was significantly associated with an increased risk of organ/space SSI (P<0.001), which was 2.8% in patients with 0-1 risk factor (RR=0.20, 95% CI: 0.11-0.35), 13.0% in patients with 2 risk factors (RR=3.64, 95% CI: 2.14-6.20) and 35.7% in patients with 3 risk factors (RR=6.41, 95% CI: 3.01-13.65). Conclusion This study is a preliminary exploratory and provides a simple risk stratification to identify the risk of postoperative organ/space SSI for patients with advanced digestive system cancer. Further research is needed to validate and generalize the results in a wider population. Clinical Trial Registration ClinicalTrials.gov, identifier NCT02715076; Chinese Clinical Trial Registry [https://www.chictr.org.cn/enindex.aspx], identifier ChiCTR-IPR-17011099.

Retrospective Clinical and Radiological Outcomes of Total Hip Arthroplasty in 51 Patients After a Mean 8.2 Years Using the Nanos® Short-stem Prosthesis

Article

Oct 2021
Surg Tech Int

Introduction: Over the past several years, femoral short-stem hip implants have become more popular as a treatment option in the field of primary hip arthroplasty for younger and more active patients. Current data on clinical outcomes and the implant survival rates in patients with short-stem implants cover a maximum of five to six years. The aim of this study was to assess the survival rates, as well as clinical and functional outcomes, in total hip arthroplasty (THA) using the Nanos® short-stem implant (Smith & Nephew, Marl, Germany) over a follow-up period exceeding 5 y. Materials and methods: This single-center retrospective study included the first 100 patients who were treated at the Department of Orthopedics at the University Hospital Halle (Saale) between January 2008 and February 2009. Ultimately, the complete data of 51 patients (54 hips) were reviewed. The follow-up period was from May to November 2017. We evaluated patient satisfaction regarding pain and function using a grading system. The Harris Hip Score and Forgotten Joint Score were obtained to evaluate functional outcome after THA. Postoperative radiographic evaluation included the measurement of leg-length discrepancy, changes in the shaft axis, femoral offset and horizontal or vertical center of rotation. Potential postoperative shaft angulation or axial shaft migration was also determined. Radiographic images were checked for radiolucent lines and heterotopic ossification using the classification systems outlined by Green and Brooker. Results: The average follow-up was 97.8 months (8.2 y). The mean patient age at follow-up was 68 y and the body mass index was 28.2 kg/m2. The mean Harris hip score at follow-up was 92.0 and the Forgotten Joint Score was 91.7 %. Survey results showed that patient satisfaction and pain perception were rated very good. No significant change in leg length was observed (mean: 0.1 mm shortening). Overall, a rather varus stem positioning was detected postoperatively (mean: 3.1°). The femoral offset was slightly reduced on average in the entire patient group (mean: -1.8 mm). In the horizontal plane, lateralization of the center of rotation was detected overall (mean: 0.7 mm). In the vertical plane, cranialization was noted (mean: 1.4 mm). The CCD angle did not change. There was no further stem migration postoperatively. Radiolucent lines occurred in 10 cases in Gruen zones 1 and 7. Heterotopic ossification occurred in stages 1 to 3 according to the Brooker classification system. We found no cases of aseptic loosening or other reasons for revision. Conclusion: The outcomes after a mean follow-up of 97.8 months (8.2 y) showed that high levels of patient satisfaction and functional outcome can be achieved with the use of a short-stem endoprosthesis. Sufficient restoration of the patient's individual anatomy paired with high survival rates makes this short-stem prosthesis a reliable implant in total hip arthroplasty.

Latest Advances in Robot-Assisted Knee Arthroplasty

Article

Oct 2021
Surg Tech Int

In the longstanding pursuit of improving alignment and functional outcome in knee arthroplasty, technological evolution leading to robotic systems has now been introduced to the mainstream orthopaedic surgical world. This technology facilitates greater accuracy in implant placement, protects soft tissues, and achieves better balancing, while also allowing the potential to be more bone conserving. Robots currently in use in orthopaedic surgery can be classified into passive or haptic semi-active surgeon-guided systems. Using a virtual model of the knee joint, the robot system guides bone cuts and facilitates precise implant placement. In addition, small changes to bone resection can be made permitting deformity correction and balancing. This is achieved on-table by dynamic referencing, which enables live objective measurement of range of movements, stability, and gap balance throughout the range of motion. Preservation of ligaments and their unnecessary releases has been shown to reduce time to recovery and allow potentially better knee kinematics. Advances in robot technology in knee arthroplasty have led to the development of a variety of systems to execute the multiple steps in this procedure including using computed tomography (CT) scans, magnetic resonance imaging (MRI) scans, plain radiographs (image based), or image-free systems. The combination of these images and on-table registering of bony landmarks allow the creation of a 3-dimensional (3D) virtual, but accurate, model of the knee during surgery. The various systems apply sculpting tools, burrs, or cutting saws to deliver the bone cuts or allow robots to guide placement of cutting blocks to ensure accurate pre-planned bone cuts. Intraoperative adjustments to bone resections can be made using a variety of tracker systems to measure joint movement and ligament balance to correct any malalignments while performing the surgery, so compound errors in the technique are avoided. Data from comparative studies suggest improved accuracy in implant placement in patients compared to conventional knee arthroplasty. Benefits of robot assistance have been demonstrated both in total knee arthroplasty and unicompartmental knee arthroplasty. Recent studies show a trend toward improved patient-reported outcomes and better patient satisfactions as well as earlier recoveries following robot-assisted knee arthroplasty. Early survivorship data has also shown a better survivorship with robot-assisted knee arthroplasty, although long-term survivorship data are awaited. An increase in familiarity, availability, and demand for this technology is driving innovations aimed at delivering a personalized approach to knee arthroplasty. This chapter will discuss the latest advances and look at the clinical research in relation to the robotic technological advancement comparing some of the different system approaches.

What Are the Sonographic Outcomes of Acute Achilles Tendon Rupture? Nonoperative Versus Surgical Repair?

Article

Full-text available

Oct 2021
Surg Tech Int

Introduction: The objective was to compare the two-year ultrasonographic outcomes in a consecutive series of patients with acute Achilles tendon rupture (ATr), either treated surgically or nonoperatively. Materials and methods: This is a prospective, single-center, consecutive series. All patients presenting with acute ATr were included and divided into two groups: surgical or nonoperative groups. At two years, patients were evaluated clinically and sonographically. The parameters studied were length of the tendon on the rupture side (LTCR) and on the contralateral side (LTCS), ratio LTCR/LTCS, maximum anteroposterior diameter on the rupture side (DAPMR), maximum surface area on the rupture side (SMR), maximum anteroposterior diameter on the contralateral side (DAPMS), and maximum surface area on the contralateral side (SMS). Morphological changes in tendon structure were reported. Results: Thirty patients were included. No difference in functional score was observed between both groups. In the nonoperative group, there is a significant difference between: LTCR and LTCS; DAPMR and DAPMS. In the surgical group, there is a significant difference between: LTCR and LTCS; DAPMR and DAPMS; SMR and SMS. There is a significant difference when comparing SMR/SMS between both groups. In terms of morphological changes in tendon structure, there were differences. Conclusion: At two years, there was no difference in functional outcomes between the two groups. In both groups, AT were lengthened and thickened without differences between groups. There was a significant difference when comparing the ratio SMR/SMS between groups. Ultrasound examination demonstrated different morphological changes in tendon structure depending on the treatment performed.

ACL Replacement with Synthetic vs. Biological Tendon Grafts: Long-Term Follow-Up Comparison Using Objective Evaluations

Article

Oct 2021
Surg Tech Int

Background and aim of the study: Anterior cruciate ligament (ACL) tears are among the most common articular injuries in sports and can be responsible for knee instability and reduced articular performance. Treatment can be either conservative or operative, and ligament reconstruction may be carried out using biological autologous grafts or synthetic materials. Several studies have sought to evaluate and compare functional results in treated patients. However, there is still very limited information available on long-term follow-up and clinical outcomes are generally evaluated only using subjective scores. In this study, we assessed long-term functional and biomechanical results in patients treated with biologic and synthetic ligaments using objective measures. Materials and methods: Patients were divided according to whether ACL reconstruction was biologic or synthetic. The Tegner activity scale was used before and after surgery. Post-operative subjective scores such as the IKDC Questionnaire and the Tegner-Lysholm score were also recorded. The Y Balance Test was used to assess global stability and mobility of the lower limb. Kinematic Rapid Assessment (KiRA) was used to evidence and estimate ligamentous laxity during the Pivot Shift and Lachman tests. Results: Clinical subjective patient and operator-dependent scores as well as objective biomechanical findings were similar and comparable in patients treated with biologic and synthetic reconstructions after more than 10 years of use. Conclusions: Both synthetic and biological tendon grafts may represent good reconstructive approaches to treat torn ACLs, and remain effective even for a long period of time if implanted in suitable target patients.

MAKO Robotic-Arm Assisted Total Knee Arthroplasty: Surgical Technique From the Office to the Operating Room

Article

Jun 2021
Surg Tech Int

Recently, robotic assistance has become more readily available to perform total knee arthroplasties. However, training can often be time consuming and there can be a learning curve. Therefore, the purpose of this article is to clearly and concisely describe the preoperative planning and surgical technique for using one version of robotic assistance, specifically the MAKO platform (MAKO Surgical Corp. [Stryker], Fort Lauderdale, Florida), for a standard osteoarthritic knee with a varus deformity that is commonly encountered by joint arthroplasty surgeons.

Risk factors for inadvertent intraoperative hypothermia in patients undergoing laparoscopic surgery: A prospective cohort study

Article

Full-text available

Sep 2021
PLOS ONE

Background: Inadvertent intraoperative hypothermia is frequent during open surgeries; however, few studies on hypothermia during laparoscopic abdominal surgery have been reported. We aimed to investigate the incidence and risk factors for hypothermia in patients undergoing laparoscopic abdominal surgery. Methods: This single-center prospective cohort observational study involved patients undergoing laparoscopic surgery between October 2018 and June 2019. Data on core body temperature and potential variables were collected. A multivariate logistic regression analysis was performed to identify the risk factors associated with hypothermia. A Cox regression analysis was used to verify the sensitivity of the results. Results: In total, 690 patients were included in the analysis, of whom 200 (29.0%, 95% CI: 26%-32%) had a core temperature < 36°C. The core temperature decreased over time, and the incident hypothermia increased gradually. In the multivariate logistic regression analysis, age (OR = 1.017, 95% CI: 1.000-1.034, P = 0.050), BMI (OR = 0.938, 95% CI: 0.880-1.000; P = 0.049), baseline body temperature (OR = 0.025, 95% CI: 0.010-0.060; P < 0.001), volume of irrigation fluids (OR = 1.001, 95% CI: 1.000-1.001, P = 0.001), volume of urine (OR = 1.001, 95% CI: 1.000-1.003, P = 0.070), and duration of surgery (OR = 1.010, 95% CI: 1.006-1.015, P < 0.001) were significantly associated with hypothermia. In the Cox analysis, variables in the final model were age, BMI, baseline body temperature, volume of irrigation fluids, blood loss, and duration of surgery. Conclusions: Inadvertent intraoperative hypothermia is evident in patients undergoing laparoscopic surgeries. Age, BMI, baseline body temperature, volume of irrigation fluids, and duration of surgery are significantly associated with intraoperative hypothermia.

Bundled-Care Program for the Prevention of Surgical-Site Infections Following Lower Extremity Total Joint Arthroplasty

Article

Jun 2021
Surg Tech Int

Surgical-site infections (SSIs) are among the most difficult-to-manage complications after lower extremity total joint arthroplasty (TJA). While the rates of most implant-related complications have decreased over time due to improvements in prosthetic materials and surgical techniques, the incidence of periprosthetic joint infections (PJIs) continues to increase. They place a tremendous economic burden on healthcare systems that is projected to reach $1.8 billion by the year 2030. A number of perioperative infection mitigation strategies exist that are often implemented concurrently to minimize the risk of these complications. A multicenter randomized controlled trial is underway to evaluate the efficacy of a bundled care program for the prevention of PJIs in lower extremity TJA. This bundle includes five infection-reduction strategies that are used pre-, peri-, and postoperatively, including: (1) povidone-iodine skin preparation and nasal decolonization; (2) iodine-alcohol surgical prepping solution; (3) iodophor-impregnated incise drapes; (4) forced-air warming blankets; and (5) negative pressure wound therapy for select patients. The aim of this review is to describe these products and their appropriate usage, review the available literature evaluating their use, and compare them with other commercially available products. Based on the available literature, each of these strategies appear to be important components for SSI-prevention protocols. We believe that implementing all five of these mitigation strategies concurrently will lead to a synergistic effect for infection control following lower extremity TJA.

Comparison of Iatrogenic Soft Tissue Trauma in Robotic-Assisted versus Manual Partial Knee Arthroplasty

Article

Aug 2021
Surg Tech Int

Partial knee arthroplasty (PKA) is performed to treat end-stage osteoarthritis in a single compartment. There are minimal data characterizing soft-tissue injuries for PKA with robotic and manual techniques. This cadaver study compared the extent of soft-tissue trauma sustained through robotic-arm assisted PKA (RPKA) and manual PKA (MPKA). Five surgeons prepared 24 cadaveric knees for medial PKA, including six MPKA controls and 18 RPKA assigned into three different workflows: RPKA-LB (six knees) - RPKA with legacy burr; RPKA-NB (six knees) - RPKA with new burr design; and RPKA-NBS (six knees) - RPKA with new burr design and oscillating saw. Two surgeons estimated trauma to the patellar tendon, quadriceps tendon, anterior cruciate ligament (ACL), medial collateral ligament (MCL), medial capsule, posterior capsule, and posterior cruciate ligament (PCLs) using a five-grade system: Grade 1 - complete soft tissue preservation; Grade 2 - ≤25%; Grade 3 - 26 to 50%; Grade 4 - 51 to 75%; and Grade 5 - ≥76% trauma. A total trauma grade was assigned by summing the grades. Kruskal-Wallis statistical tests were used to assess outcomes. When compared to the MPKA group, all RPKA subgroups had lower total trauma grading (p<0.01), lower posterior capsular damage (p<0.01), and less severe ACL damage (p<0.01). The analysis demonstrated no significant difference between the three RPKA workflows. As this study was performed using cadaveric specimens, additional investigations are necessary to determine associations between robotic or manual-assisted technique, observed soft tissue damage, and postoperative clinical outcomes following PKA.

Robotic-Assisted Total Hip Arthroplasty in Patients Who Have Developmental Hip Dysplasia

Article

Jul 2021
Surg Tech Int

Introduction: Total hip arthroplasty (THA) in the setting of developmental dysplasia of the hip (DDH) presents more inherent complexities than routine primary THA for osteoarthritis. These include acetabular bone deficiency, limb length discrepancy (LLD), and abnormal femoral anteversion. Three-dimensional planning and robot-assisted (RA) bone preparation may simplify these complex procedures and make them more reproducible. The purpose of this study was to evaluate radiographic and clinical outcomes in a cohort of patients who had DDH and underwent an RA THA. Materials and methods: We retrospectively analyzed 26 DDH patients who underwent RA THA by a single surgeon between 2013 and 2019. Their mean age was 54 years (range, 29 to 72 years) and mean follow up was approximately two years. Medical records were reviewed for demographics, clinical scores, Crowe classifications, and complications. There were thirteen Crowe I and seven Crowe II DDH hips, who were routinely managed with primary cementless implants. Two patients who had Crowe III and four patients who had Crowe IV DDH were also identified. All hips were reconstructed with cementless hemispherical acetabular components with or without the use of screws, but no acetabular augments or bulk allografts. Implants allowing control of femoral anteversion were selected in 23.1% of cases, including all six cases with Crowe III or IV dysplasia, and the need for these implants was uniformly identified using preoperative information about femoral version provided by the three-dimensional planning software. No patient was managed with a shortening femoral osteotomy. Postoperative radiographs were examined for LLD, center of rotation (COR), cup position (inclination and anteversion), and component osseous-integration. Results: Mean radiographic LLD was 1.7mm (range, -9 to +14) in patients who had Crowe I DDH, and there was no clinical LLDs greater than 5mm observed. Although patients who had Crowe II and greater DDH had a mean radiographic LLD of -11.6mm (range, -26 to +2.2), again no clinical LLD greater than 5mm was observed other than one patient who had bilateral Crowe II DDH in whom 10mm of clinical lengthening was accepted at the index arthroplasty with the plan to match lengths when her contralateral THA was performed. There were no cases of dislocation or acetabular fixation failure. One patient who had a femoral deformity and an intra-osseous blade plate from a prior femoral osteotomy suffered a failure of femoral osseous-integration, resulting in revision. A 32-point increase in mean modified Harris Hip Score (mHHS) was found (p=0.002), from 48 points preoperatively to 80 points postoperatively. Discussion: RA THA provides an excellent option for the arthroplasty surgeon to both preoperatively localize and characterize the acetabular deficiency, while providing a targeted, optimal, and secure placement of the components intraoperatively. Our results suggest favorable outcomes when compared to previous research on manual THA in DDH. Further studies, including comparative analyses, could discern possible advantages over traditional THA without robotic assistance in DDH. Conclusion: Total hip arthroplasty (THA) in the setting of developmental dysplasia presents more inherent complexities than routine primary THA. Robotic-assisted THA may simplify these complex procedures.

Comparison of two forced air warming systems for prevention of intraoperative hypothermia in carcinoma colon patients: a prospective randomized study

Article

Full-text available

Feb 2022
J Clin Monit Comput

Hypothermia is common occurrence in patients undergoing colonic surgeries. We hypothesized that the underbody forced air warming blankets will be better than conventional over-body forced air warming blankets for prevention of hypothermia during laparoscopic colon surgeries. After ethics approval, sixty patients undergoing elective laparoscopic colon surgeries were randomly divided into two groups to receive warming by underbody forced air warming blanket (n = 30) or over-body forced air warming blanket (n = 30). In the operating room, epidural catheter was inserted and thereafter warming was started with the forced air warmer with temperature set at 44 °C. Intraoperatively core temperature (using nasopharyngeal probe), vitals, incidence of postoperative shivering and time to reach Aldrete Score of 10 in the postoperative period were recorded. The core temperature was higher with an underbody blanket at 60 min (36.1 ± 0.5 °C vs. 35.7 ± 0.5 °C, P = 0.005), 90 min (35.9 ± 0.5 °C vs. 35.6 ± 0.5 °C, P = 0.009), 120 min (35.9 ± 0.5 °C vs. 35.5 ± 0.4 °C, P = 0.007), and 150 min (35.9 ± 0.5 °C vs. 35.6 ± 0.4 °C, P = 0.011). In the post anesthesia care unit, the time to reach an Aldrete score of 10 was also less in the underbody blanket group (14.3 ± 2.5 min vs. 16.8 ± 3.6 min) (P = 0.003). However, there were no clinically meaningful differences in any outcome. Underbody and over-body blankets were comparably effective in preventing hypothermia in patients undergoing laparoscopic colorectal surgery under general anaesthesia. Trial registration CTRI (2019/06/019,576). Date of Registration: June 2019, Prospectively registered.

Effects of a preoperative forced-air warming system for patients undergoing video-assisted thoracic surgery: A randomized controlled trial

Article

Full-text available

Nov 2020

Background: The incidence of intraoperative hypothermia is still high despite the proposal of different preventive measures during thoracoscopic surgery. This randomized control study evaluated the effects of 30-minute prewarming combined with a forced-air warming system during surgery to prevent intraoperative hypothermia in patients undergoing video-assisted thoracic surgery under general anesthesia combined with erector spinae nerve block. Methods: Ninety-eight patients were randomly and equally allocated to prewarming or warming groups (n = 49 each). The primary outcome was the incidence of intraoperative hypothermia. Secondary outcomes were core temperature, irrigation and infused fluid, estimated blood loss, urine output, type of surgery, intraoperative anesthetic dosage, hemodynamics, recovery time, the incidence of postoperative shivering, thermal comfort, postoperative sufentanil consumption and pain intensity, patient satisfaction, and adverse events. Results: The incidence of intraoperative hypothermia was significantly lower in the prewarming group than the warming group (12.24% vs 32.65%, P = .015). Core temperature showed the highest decrease 30 minutes after surgery start in both groups; however, the rate was lower in the prewarming than in the warming group (0.31 ± 0.04°C vs 0.42 ± 0.06°C, P < .05). Compared with the warming group, higher core temperatures were recorded for patients in the prewarming group from T1 to T6 (P < .05). Significantly fewer patients with mild hypothermia were in the prewarming group (5 vs 13, P = .037) and recovery time was significantly reduced in the prewarming group (P < .05). Although the incidence of postoperative shivering was lower in the prewarming group, it was not statistically significant (6.12% vs 18.37%, P = .064). Likewise, the shivering severity was similar for both groups. Thermal comfort was significantly increased in the prewarming group, although patient satisfaction was comparable between the 2 groups (P > .05). No adverse events occurred associated with the forced-air warming system. Both groups shared similar baseline demographics, type of surgery, total irrigation fluid, total infused fluid, estimated blood loss, urine output, intraoperative anesthetic dosage, hemodynamics, duration of anesthesia and operation time, postoperative sufentanil consumption, and pain intensity. Conclusion: In patients undergoing video-assisted thoracic surgery, prewarming for 30 minutes before the induction of anesthesia combined with a forced-air warming system may improve perioperative core temperature and the thermal comfort, although the incidence of postoperative shivering and severity did not improve.

Prevalence and multivariable factors associated with inadvertent intraoperative hypothermia in video-assisted thoracoscopic surgery: A single-center retrospective study

Article

Full-text available

Jan 2020
BMC Anesthesiol

Background: Inadvertent intraoperative hypothermia increases the risk of adverse events, but its related risk factors have not been defined in video-assisted thoracoscopic surgery (VATS). This study aimed at analyzing the prevalence and factors related to inadvertent intraoperative hypothermia in adults undergoing elective VATS under general anesthesia. Methods: This was a retrospective study using data from the Peking University People's Hospital from January through December, 2018. Data were collected on age, sex, height, weight, American Society of Anesthesiologists physical status, the duration of preparation and surgery, timing of surgery, surgery types, anesthesia types, intraoperative core temperature and the length of stay (LOS) in the hospital from the electronic database in our center. Patients were covered with a cotton blanket preoperatively and the surgical draping during the operation. A circulation-water warming mattress set to 38 °C were placed under the body of the patients. Inadvertent intraoperative hypothermia was identified as a core temperature monitored in nasopharynx < 36 °C. Multivariate logistic regression analysis was used to identify independent risk factors of hypothermia. Results: We found that 72.7% (95% CI 70.5 to 75.0%) of 1467 adult patients who underwent VATS suffered hypothermia during surgery. The factors associated with inadvertent intraoperative hypothermia included age (OR = 1.23, 95% CI 1.11 to 1.36, p < 0.001), BMI (OR = 1.83, 95% CI 1.43 to 2.35, p < 0.001), the duration of preparation (OR = 1.01, 95% CI 1.00 to 1.02, p = 0.014), the duration of surgery (OR = 2.10, 95% CI 1.63 to 2.70, p < 0.001), timing of surgery (OR = 1.64, 95% CI 1.28 to 2.12, p < 0.001), ambient temperature in the operating room (OR = 0.67, 95% CI 0.53 to 0.85, p = 0.001) and general anesthesia combined with paravertebral block after induction of anesthesia (OR = 2.30, 95% CI 1.31 to 4.03, p = 0.004). The average LOS in the hospital in the hypothermia group and the normothemic group was 9 days and 8 days, respectively (p < 0.001). Conclusions: We highlight the high prevalence of inadvertent intraoperative hypothermia during elective VATS and identify key risk factors including age, duration of surgery more than 2 h, surgery in the morning and general anesthesia combined with paravertebral block (PVB) after intubation. We also find that hypothermia did prolong the LOS in the hospital.

Perioperative Hypothermia in Robotic-Assisted Thoracic Surgery: Incidence, Risk Factors and Associations with Post-Operative Outcomes

Article

Oct 2023
J THORAC CARDIOV SUR

Research Progress of Body Temperature Protection with Physical and Pharmacological Intervention in Perioperative Temperature Management

Article

Full-text available

Jan 2023

·麦麦提艾力麦尔哈巴

A Warm Air Blanket is Superior to a Heated Mattress in Preventing Perioperative Hypothermia in Orthopedic Arthroplasties, a Time-Series Analyses

Article

Aug 2023
J ARTHROPLASTY

Background: Hypothermia is a common perioperative problem that can lead to severe complications. We evaluated whether a heated mattress (HM) is superior to a warm air blanket (WA) in preventing perioperative hypothermia in patients undergoing total hip arthroplasty (THA) or total knee arthroplasty (TKA). Methods: A retrospective cohort study was performed in a teaching hospital and data was collected for all patients undergoing THA or TKA between January 1, 2015 and May 1, 2022. We used logistic and linear regressions to analyze hypothermia occurrence and important complications. The result was adjusted for confounders and time and was present in all subgroups and after imputation of missing warming methods. Results: In total, 4,683 out of 5,497 patients had information on type of heating. We found more perioperative hypothermia in patients treated with a HM compared to a WA for both THA (Odds Ratio-adjusted (ORadj) 1.42 [1.0-1.6] P=0.06) and TKA (ORadj 2.10 [1.5-3.0] P<0.01). There was no difference in postoperative infections between groups (all between 0.5 and 1.3%). Patients who had a HM significantly stayed longer in the post-operative ward (a mean difference of 4 [TKA] to 6 [THA] minutes, P<0.01), but there was no difference in hospital stay. Conclusion: A warm air blanket is superior compared to a heated mattress in preventing perioperative hypothermia, with no increased risk of complications. Patients who have a HM stayed longer at the post-operative ward, potentially because of higher hypothermia rates. Therefore, it is suggested to use a warm air blanket instead of a heated mattress.

Cerrahi Hastalarında İstenmeyen Hipoterminin Önlenmesi ve Yönetimi: Geleneksel Derleme

Article

Full-text available

Jan 2023

Self‐warming blanket versus forced‐air warming blanket during total knee arthroplasty under spinal anaesthesia: A randomised non‐inferiority trial

Article

May 2023

Background: Arthroplasty patients are at high risk of hypothermia. Pre-warming with forced air has been shown to reduce the incidence of intraoperative hypothermia. There is, however, a lack of evidence that pre-warming with a self-warming (SW) blanket can reduce the incidence of perioperative hypothermia. This study aims to evaluate the effectiveness of an SW blanket and a forced-air warming (FAW) blanket peri-operatively. We hypothesised that the SW blanket is inferior to the FAW blanket. Methods: In total, 150 patients scheduled for primary unilateral total knee arthroplasty under spinal anaesthesia were randomised to this prospective study. Patients were pre-warmed with SW blanket (SW group) or upper-body FAW blanket (FAW group) set to 38°C for 30 min before spinal anaesthesia induction. Active warming was continued with the allocated blanket in the operating room. If core temperature fell below 36°C, all patients were warmed using the FAW blanket set to 43°C. Core and skin temperatures were measured continuously. The primary outcome was core temperature on admission to the recovery room. Results: Both methods increased mean body temperature during pre-warming. However, intraoperative hypothermia occurred in 61% of patients in the SW group and in 49% in the FAW group. The FAW method set to 43°C could rewarm hypothermic patients. Core temperature did not differ between groups on admission to the recovery room, p = .366 (CI: -0.18-0.06). Conclusions: Statistically, the SW blanket was non-inferior to the FAW method. Yet, hypothermia was more frequent in the SW group, requiring rescue warming as we strictly held to the NICE guideline. Trial registration: Clinicaltrials.gov identifier: NCT03408197.

Risk Factors for Intraoperative Hypothermia during Holmium Laser Enucleation of the Prostate

Article

Mar 2023
UROL INT

Introduction: Holmium laser enucleation of the prostate (HoLEP) is considered a size-independent gold standard for benign prostatic hyperplasia (BPH), and there is no upper limit of prostate weight that can be treated. Tissue retrieval can be time-consuming in cases of significant prostatic enlargement, which may lead to intraoperative hypothermia. As there are few studies on perioperative hypothermia in HoLEP, we conducted a retrospective study of patients who underwent HoLEP at our hospital. Methods: The data of 147 patients who underwent HoLEP at our hospital were retrospectively collected and analyzed for the occurrence of intraoperative hypothermia (temperature <36°C); age, body mass index (BMI), anesthesia method, body temperature, total fluid infusion, operation time, and irrigation fluid were the explanatory variables. Results: Intraoperative hypothermia was observed in 46 of 147 patients (31.3%). Simple logistic regression analysis showed that age (odds ratio [OR]: 1.07, 95% confidence interval [CI]: 1.01-1.13, p = 0.021), BMI (OR: 0.84, 95% CI: 0.72-0.96, p = 0.017), spinal anesthesia (OR: 4.92, 95% CI: 1.86-14.99, p = 0.002), and surgical time (OR: 1.04, 95% CI: 1.01-1.06, p = 0.006) were predictors of hypothermia. The decrease in body temperature was more pronounced with longer-duration surgery and reached 0.58°C at 180 min. Conclusion: General anesthesia, instead of spinal anesthesia, is recommended in high-risk patients with advanced age or low BMI to avoid intraoperative hypothermia during HoLEP. Two-stage morcellation may be considered for large adenomas, when a prolonged operative time and hypothermia are anticipated.

Research Progress of Perioperative Hypothermia

Article

Full-text available

Jan 2023

芝燕李

A Nomogram for Predicting Unplanned Intraoperative Hypothermia in Patients With Colorectal Cancer Undergoing Laparoscopic Colorectal Procedures

Article

Jan 2023

Unplanned intraoperative hypothermia is a complication that can lead to a variety of negative outcomes, such as cardiovascular events. We aimed to develop and validate an intraoperative hypothermia risk prediction nomogram for patients with colorectal cancer undergoing laparoscopic colorectal procedures. We conducted a prospective cohort study with 1,091 patients (ie, 765 in the training cohort, 326 in the validation cohort) from October 2020 to November 2021. We included six predictors in the nomogram model: body mass index, diabetes diagnosis, ambient temperature, ambient humidity, duration of surgery, and use of a forced‐air warmer. The model performed well, and the area under the curve was 0.855. These results, together with an external validation value, mean that health care professionals can use the nomogram to calculate the intraoperative hypothermia risk for patients undergoing laparoscopic colorectal procedures and make clinical decisions based on the results.

Thermal suit connected to a forced‐air warming unit for preventing intraoperative hypothermia: A randomised controlled trial

Article

Sep 2020
ACTA ANAESTH SCAND

Background: Inadvertent intraoperative hypothermia is a common occurrence in surgical patients. A thermal suit is an option for passive insulation. However, active warming is known to be more effective. Therefore, we hypothesised a forced-air warming unit connected to the thermal suit is superior to a commercial forced-air warming blanket and a warming mattress in breast cancer surgery. Methods: Forty patients were randomised to this prospective, clinical trial to wear either the thermal suit or conventional hospital clothes under general anaesthesia. The Thermal suit group had a forced-air warming unit set to 38 °C and connected to the legs of the suit. The Hospital clothes group had a lower body blanket set to 38 °C and a warming mattress set to 37 °C. Core temperature was measured with zero-heat-flux sensor. The primary outcome was core temperature on admission to the recovery room. Results: There was no difference in mean core temperatures at anaesthetic induction (P=0.4) or on admission to the recovery room (P=0.07). One patient in the Thermal suit group (5%) vs. six patients in the Hospital clothes group (32%) suffered from intraoperative hypothermia (P=0.04, 95% CI 1.9 to 49%). Mean skin temperatures were higher in the Thermal suit group during anaesthesia. No burns or skin irritations were reported. Two patients in the Thermal suit group sweated. Conclusions: A thermal suit connected to a forced-air warming unit was not superior to a commercial forced-air warming blanket, although the incidence of intraoperative hypothermia was lower in patients treated with a thermal suit.

Effect of Perioperative Active Body Surface Warming Systems on Analgesic and Clinical Outcomes: A Systematic Review and Meta-analysis of Randomized Controlled Trials

Article

Sep 2020
ANESTH ANALG

Background: Inadvertent perioperative hypothermia is a common complication of surgery, and active body surface warming (ABSW) systems are used to prevent adverse clinical outcomes. Prior data on certain outcomes are equivocal (ie, blood loss) or limited (ie, pain and opioid consumption). The objective of this study was to provide an updated review on the effect of ABSW on clinical outcomes and temperature maintenance. Methods: We conducted a systematic review of randomized controlled trials evaluating ABSW systems compared to nonactive warming controls in noncardiac surgeries. Outcomes studied included postoperative pain scores and opioid consumption (primary outcomes) and other perioperative clinical variables such as temperature changes, blood loss, and wound infection (secondary outcomes). We searched Ovid MEDLINE daily, Ovid MEDLINE, EMBASE, CINHAL, Cochrane CENTRAL, and Web of Science from inception to June 2019. Quality of evidence (QoE) was rated according to the Grading of Recommendations, Assessment, Development and Evaluations (GRADE) approach. Subgroup analysis sought to determine the effect of preoperative + intraoperative warming versus intraoperative warming alone. Metaregression evaluated the effect of year of publication, use of neuromuscular blockers, anesthesia, and surgery type on outcomes. Results: Fifty-four articles (3976 patients) were included. Pooled results demonstrated that ABSW maintained normothermia compared to controls, during surgery (30 minutes postinduction [mean difference {MD}: 0.3°C, 95% confidence interval {CI}, 0.2-0.4, moderate QoE]), end of surgery (MD: 1.1°C, 95% CI, 0.9-1.3, high QoE), and up to 4 hours postoperatively (MD: 0.3°C, 95% CI, 0.2-0.5, high QoE). ABSW was not associated with difference in pain scores (<24 hours postoperatively, moderate to low QoE) or perioperative opioid consumption (very low QoE). ABSW increased patient satisfaction (MD: 2.2 points, 95% CI, 0.9-3.6, moderate QoE), reduced blood transfusions (odds ratio [OR] = 0.6, 95% CI, 0.4-1.0, moderate QoE), shivering (OR = 0.2, 95% CI, 0.1-0.4, high QoE), and wound infections (OR = 0.3, 95% CI, 0.2-0.7, high QoE). No significant differences were found for fluid administration (low QoE), blood loss (very low QoE), major adverse cardiovascular events (very low QoE), or mortality (very low QoE). Subgroup analysis and metaregression suggested increased temperature benefit with pre + intraoperative warming, use of neuromuscular blockers, and recent publication year. ABSW seemed to confer less temperature benefit in cesarean deliveries and neurosurgical/spinal cases compared to abdominal surgeries. Conclusions: ABSW is effective in maintaining physiological normothermia, decreasing wound infections, shivering, blood transfusions, and increasing patient satisfaction but does not appear to affect postoperative pain and opioid use.

Preventing Inadvertent Hypothermia in Patients Undergoing Major Spinal Surgery: A Nonrandomized Controlled Study of Two Different Methods of Preoperative and Intraoperative Warming

Article

Jun 2019

Purpose: To evaluate if a Full Access Underbody (FAU) blanket used preoperatively and intraoperatively in patients undergoing major spinal surgery prevents hypothermia compared with current practice and to explore patients' experiences of comfort. Design: A nonrandomized controlled trial. Methods: Sixty patients were included, 30 in each group. Temperature was assessed on arrival, after connecting to the bladder catheter, and at the start and end of surgery. In the FAU group, comfort was evaluated at arrival and after 10 minutes of prewarming. Findings: The incidence of hypothermia at the start of surgery was significantly lower (relative risk [95% confidence interval], 0.28 [0.13 to 0.59]). Before prewarming, 77% felt comfortable, 20% cold, and 3% hot. After prewarming 60% felt comfortable, 37% hot, and 3% very hot. Conclusions: Patients using the FAU blanket had a 72% lower incidence of hypothermia at the start of the operation. Attention to thermal comfort during surgery is important.

Normothermia is Best Achieved by Warming Above and Below with Pre-warming Adjunct: A Comparison of Conductive Fabric Versus Forced-air and Water

Article

May 2019
Surg Tech Int

Background: Although forced-air warming is the most commonly used method for perioperative patient warming, it is fundamentally problematic because it disturbs the carefully designed airflow in the operating room. Because unintended hypothermia has significant consequences, there is a need for more effective warming strategies. The effectiveness of warming technologies that apply heat through the skin is based on surface-area contact with the heat source and the duration of pre-warming. Therefore, we sought to test the therapeutic effectiveness of combined above- and below-warming therapies. Our hospital prohibits forced-air warming before the patient is draped, so a secondary goal was to determine the effect of preoperative warming using a system that does not interfere with airflow in the operating room. Methods: We prospectively randomized 35 patients undergoing total knee arthroplasty into two groups: 1) forced-air warming/water mattress, using both WarmTouch® upper-body forced-air warming (Medtronic/Covidien Inc., Dublin, Ireland) and a Norm-O-Temp® underbody water mattress (CSZ/Gentherm Inc., Cincinnati, OH, USA), and 2) conductive fabric warming, using a HotDog® electric upper-body blanket (Augustine Temperature Management LLC, Eden Prairie, MN, USA) and a HotDog® underbody mattress. Results: Throughout the surgical procedure, group 2 patients had significantly higher temperatures; this group experienced superior pre-warming during preoperative preparations and thus the redistribution temperature drop following the induction of anesthesia was reduced. Both groups achieved 100% normothermia by the end of surgery. Conclusion: Based solely on the temperatures at the end of surgery, these data indicate that forced-air warming in conjunction with a water mattress warming system is as effective as a conductive fabric electric warming system alone.

Incidence of Inadvertent Intraoperative Hypothermia and Its Risk Factors in Patients Undergoing General Anesthesia in Beijing: A Prospective Regional Survey

Article

Full-text available

Sep 2015
PLOS ONE

Background/objective: Inadvertent intraoperative hypothermia (core temperature <360 C) is a recognized risk in surgery and has adverse consequences. However, no data about this complication in China are available. Our study aimed to determine the incidence of inadvertent intraoperative hypothermia and its associated risk factors in a sample of Chinese patients. Methods: We conducted a regional cross-sectional survey in Beijing from August through December, 2013. Eight hundred thirty patients who underwent various operations under general anesthesia were randomly selected from 24 hospitals through a multistage probability sampling. Multivariate logistic regression analyses were applied to explore the risk factors of developing hypothermia. Results: The overall incidence of intraoperative hypothermia was high, 39.9%. All patients were warmed passively with surgical sheets or cotton blankets, whereas only 10.7% of patients received active warming with space heaters or electric blankets. Pre-warmed intravenous fluid were administered to 16.9% of patients, and 34.6% of patients had irrigation of wounds with pre-warmed fluid. Active warming (OR = 0.46, 95% CI 0.26-0.81), overweight or obesity (OR = 0.39, 95% CI 0.28-0.56), high baseline core temperature before anesthesia (OR = 0.08, 95% CI 0.04-0.13), and high ambient temperature (OR = 0.89, 95% CI 0.79-0.98) were significant protective factors for hypothermia. In contrast, major-plus operations (OR = 2.00, 95% CI 1.32-3.04), duration of anesthesia (1-2 h) (OR = 3.23, 95% CI 2.19-4.78) and >2 h (OR = 3.44, 95% CI 1.90-6.22,), and intravenous un-warmed fluid (OR = 2.45, 95% CI 1.45-4.12) significantly increased the risk of hypothermia. Conclusions: The incidence of inadvertent intraoperative hypothermia in Beijing is high, and the rate of active warming of patients during operation is low. Concern for the development of intraoperative hypothermia should be especially high in patients undergoing major operations, requiring long periods of anesthesia, and receiving un-warmed intravenous fluids.

The effects of anesthetic technique and ambient temperature on thermoregulation in lower extremity surgery

Article

Full-text available

Jan 2013
J ANESTH

Purpose: The purpose of our study was to determine the effects of anesthetic technique and ambient temperature on thermoregulation for patients undergoing lower extremity surgery. Methods: Our study included 90 male patients aged 18-60 years in American Society of Anesthesiologists Physical Status groups I or II who were scheduled for lower extremity surgery. Patients were randomly divided into three groups according to anesthetic technique: general anesthesia (GA), epidural anesthesia (EA), and femoral-sciatic block (FS). These groups were divided into subgroups according to room temperature: the temperature for group I was 20-22 °C and that for group II was 23-25 °C. Therefore, we labeled the groups as follows: GA I, GA II, EA I, EA II, FS I, and FS II. Probes for measuring tympanic membrane and peripheral temperature were placed in and on the patients, and mean skin temperature (MST) and mean body temperature (MBT) were assessed. Postoperative shivering scores were recorded. Results: During anesthesia, tympanic temperature and MBT decreased whereas MST increased for all patients. There was no significant difference between tympanic temperatures in either the room temperature or anesthetic method groups. MST was lower in group GA I than in group GA II after 5, 10, 15, 20, 60 and 90 min whereas MBT was significantly lower at the basal level (p < 0.05). MST after 5 min was significantly lower in group GA I than in group FS I (p < 0.05). Shivering score was significantly higher in group GA I (p < 0.05). Conclusions: There were no significant differences in thermoregulation among anesthetic techniques. Room temperature affected thermoregulation in Group GA.

Thermal comfort during surgical operations

Article

Full-text available

Jul 1968
J Hyg

Visits have been made to thirty operating suites in the British Isles. Each suite was visited three times at approximately 4-month intervals and observations made on an average of five half-day working sessions on each occasion. Measurements were made of air temperature, humidity, air movement and radiation temperature and many details of the suites and working conditions recorded. At suitable intervals the operating room staff were questioned as to their feelings of thermal comfort using Bedford's 7-point scale. Over 2500 sets of replies were obtained. Visible sweating was also noted. The effect on comfort and the extent of visible sweating of the many items recorded was then explored by means of a sequential multiple regression analysis. Although air temperature was by far the most important factor affecting thermal comfort, all the variables named above exerted a significant effect. In addition, a number of other conditions including age, sex and race produced minor differences. Surgeons and anaesthetists were found to differ from other staff in their thermal preferences, the surgeons liking a cooler and the anaesthetists a warmer environment. Although most surgeons were comfortable at temperatures around 66·5°F. (19°C.), at 50% relative humidity and 25 ft./min. air movement with the average amount of thermal radiation from the operating room lamp, it would be necessary to keep the temperature down to 64·5°F. (18°C.) if no more than one surgeon in twenty was to be uncomfortably hot. At this temperature nearly half the anaesthetists, who mostly preferred temperatures around 71°F. (21·5°C.), would feel too cold. Variation in the clothing worn by different staff members seems to be the only way of resolving this difficulty. The average temperature in the operating rooms visited was over 72°F. (22°C.), and 75°F. (24°C.) was exceeded on about 25% of occasions.

Mild Intraoperative Hypothermia Prolongs Postanesthetic Recovery

Article

Full-text available

Dec 1997

Intraoperative hypothermia is common and persists for several hours after surgery. Hypothermia may prolong immediate recovery by augmenting anesthetic potency, delaying drug metabolism, producing hemodynamic instability, or depressing cognitive function. Accordingly, the authors tested the hypothesis that intraoperative hypothermia prolongs postoperative recovery. Patients undergoing elective major abdominal surgery (n = 150) were anesthetized with isoflurane, nitrous oxide, and fentanyl. They were randomly assigned to routine thermal management (hypothermia) or extra warming (normothermia). Postoperative surgical pain was treated with patient-controlled analgesia. Fitness for discharge from the postanesthesia care unit was evaluated at 20-min intervals by investigators blinded to group assignment and postoperative core temperatures. Scoring was based on a modification of a previously published system that included activity, ventilation, consciousness, and hemodynamic responses. Patients were considered fit for discharge when they sustained a score of 80% (13 points) for at least two consecutive measurement periods. Morphometric characteristics and anesthetic management were similar in each group. Final intraoperative core temperatures differed by approximately 2 degrees C: 34.8 +/- 0.6 versus 36.7 +/- 0.6 degrees C (mean +/- SD, P < 0.001). Postoperative pain scores and postoperative use of patient-controlled opioid were similar. Hypothermic patients required approximately 40 min longer (94 +/- 65 vs. 53 +/- 36 min) to reach fitness for discharge, even when return to normothermia was not a criterion (P < 0.001). Duration of recovery in the two groups differed by approximately 90 min when a core temperature >36 degrees C was also required (P < 0.001). Maintaining core normothermia decreases the duration of postanesthetic recovery and may, therefore, reduce costs of care.

Optimal Depth for Nasopharyngeal Temperature Probe Positioning

Article

Mar 2016

Background: The nasopharynx is considered 1 of the 4 generally reliable core temperature measurement sites. But curiously, there is no consensus on how far past the nares to insert the probe. Insertion depth is likely to influence the accuracy of nasopharyngeal temperature measurements because probes near the nares will be cooled by ambient air; similarly, probes inserted too far may approach the airway and be cooled by ventilation gases. We thus determined the range of nasopharyngeal probe insertion depths that best approximate reference core temperature measured in the distal esophagus. Methods: In 36 adults undergoing noncardiac surgery with endotracheal intubation, we inserted a nasopharyngeal thermometer 20 cm past the nares and an esophageal temperature probe 40 cm from the incisors. The nasopharyngeal probe was withdrawn sequentially 2 cm at a time at 5-minute intervals. Pairs of nasopharyngeal and reference distal esophageal temperatures were then compared and summarized by Bland and Altman methods. Results: All nasopharyngeal probe insertion depths between 10 and 20 cm past the nares provided temperatures similar to reference distal esophageal temperatures. At those depths, the bias was typically approximately -0.1°C, with SD of approximately ±0.15°C; the limits of agreement thus were easily within our a priori specified clinically acceptable range of -0.5°C and 0.5°C. Conclusions: Any nasopharyngeal probe insertion depth between 10 and 20 cm well represents core temperature in adults having noncardiac surgery.

An Evaluation of a Zero-Heat-Flux Cutaneous Thermometer in Cardiac Surgical Patients

Article

Jul 2014
ANESTH ANALG

Background: Although core temperature can be measured invasively, there are currently no widely available, reliable, noninvasive thermometers for its measurement. We thus compared a prototype zero-heat-flux thermometer with simultaneous measurements from a pulmonary artery catheter. Specifically, we tested the hypothesis that zero-heat-flux temperatures are sufficiently accurate for routine clinical use. Methods: Core temperature was measured from the thermistor of a standard pulmonary artery catheter and with a prototype zero-heat-flux deep-tissue thermometer in 105 patients having nonemergent cardiac surgery. Zero-heat-flux probes were positioned on the lateral forehead and lateral neck. Skin surface temperature probes were attached to the forehead just adjacent to the zero-heat-flux probe. Temperatures were recorded at 1-minute intervals, excluding the period of cardiopulmonary bypass, and for the first 4 postoperative hours. Zero-heat-flux and pulmonary artery temperatures were compared with bias analysis; differences exceeding 0.5°C were considered to be potentially clinically important. Results: The mean duration in the operating room was 279 ± 75 minutes, and the mean cross-clamp time was 118 ± 50 minutes. All subjects were monitored for an additional 4 hours in the intensive care unit. The average overall difference between forehead zero-heat-flux and pulmonary artery temperatures (i.e., forehead minus pulmonary artery) was -0.23°C (95% limits of agreement of ±0.82); 78% of the differences were ≤0.5°C. The average intraoperative temperature difference was -0.08°C (95% limits of agreement of ±0.88); 84% of the differences were ≤0.5°C. The average postoperative difference was -0.32°C (95% limits of agreement of ±0.75); 84% of the differences were ≤0.5°C. Bias and precision values for neck site were similar to the forehead values. Uncorrected forehead skin temperature showed an increasing negative bias as core temperature decreased. Conclusions: Core temperature can be noninvasively measured using the zero-heat-flux method. Bias was small, but precision was slightly worse than our designated 0.5°C limits compared with measurements from a pulmonary artery catheter.

Decreased Fresh Gas Flow Cannot Compensate for an Increased Operating Room Temperature in Maintaining Body Temperature During Donor Hepatectomy for Living Liver Donor Hepatectomy

Article

Apr 2010

The purpose of this study was to compare the effect of various combinations of fresh gas flow (FGF) of anesthesia and different ambient operation room temperatures (ORT) on changes in nasopharyngeal temperature (NT) among living donors undergoing partial hepatectomy. The anesthesia records of 167 patients were reviewed retrospectively. The patients were allocated into 4 groups: GI (n=37): isoflurane in 2 L FGF and at typical ambient ORT (19 degrees C-21 degrees C); GII (n=11) isoflurane in 1 L FGF and 1 L air at typical ORT; GIII (n=31) isoflurane in 0.5 L FGF at typical ORT; and GIV (n=88) isoflurane in 0.5 L FGF at ORT of 24 degrees C. The changes in NT were compared using a two-way repeated measure analysis of variance (ANOVA) followed by Bonferroni post hoc tests. Changes of NTs of GIV were significantly higher compared with the other 3 groups, whereas the changes of NTs were the same among GI, GII, and GIII. FGF of different volumes seemed to have no significant effect on intraoperative changes of NT in regular ORT. Low-flow anesthesia combined with ORT of 24 degrees C provided significantly higher NTs at all measured points compared with GI, GII, and GIII.

Noninvasive Temperature Monitoring in Postanesthesia Care Units

Article

Jul 2009
ANESTHESIOLOGY

Initial postoperative core temperature is a physician and hospital performance measure. However, the extent to which core temperature changes during emergence from anesthesia and transport from the operating room to the postanesthesia care unit (PACU) remains unknown. Similarly, the accuracy of many noninvasive temperature-monitoring methods used in the PACU has yet to be quantified. This study, therefore, quantified the change in core temperature occurring during emergence and transport and evaluated the accuracy and precision of eight noninvasive thermometers in the PACU. In 50 patients having laparoscopic surgery, the authors measured temperatures upon PACU arrival and 30 and 60 min thereafter. Monitoring methods included oral, axillary, temporal artery, forehead skin-surface, forehead liquid-crystal display, infrared aural canal, deep forehead, and deep chest. Bladder temperature was used as the reference and was also measured at the end of surgery. The primary outcome was agreement between individual temperatures from each method and bladder temperature in the PACU. A priori, the authors chose 0.5 degrees C as a clinically important temperature deviation. Bladder temperature increased 0.2 +/- 0.3 degrees C (95% confidence interval 0.1 to 0.3 degrees C), P < 0.001, during transport. None of the tested noninvasive thermometers was consistently within 0.5 degrees C of bladder temperature. However, oral, deep forehead, and temporal artery temperatures were significantly better than other methods and agreed reasonably well with bladder temperature. Invasive temperature monitoring available intraoperatively is more accurate than any generally available postoperative methods. Physician performance measures should therefore not be based exclusively on postoperative temperatures. Among the generally available postoperative monitoring methods, electronic oral thermometry appears to be the best.

Effects of Different Operating Room Temperatures on the Body Temperature Undergoing Live Liver Donor Hepatectomy

Article

Nov 2008
TRANSPL P

We sought to compare the effects of operation room temperature (ORT) at typical ambient environment (19-21 degrees C) and ORT at 24 degrees C on the core temperature of patients undergoing living donor hepatectomy. Sixty-two patients undergoing living donor hepatectomy were divided into 2 groups. In group I (n = 31), surgery was performed at typical ambient ORT, and in group II (n = 31) in ORT at 24 degrees C. Anesthesia and measures to prevent heat loss, except ORT, were all the same. Nasopharyngeal temperature (NT) was recorded after anesthesia induction, then hourly until completion of the operation. Changes in NTs were analyzed as well as patient age, weight, anesthetic duration, blood loss, intravenous fluids, total urine output, and pre- and postoperative hemoglobin and hematocrit values. The Mann-Whitney U test was used for comparisons between groups. The patient's characteristics between groups were not statistically different. However, a significantly higher core temperature was noted in group II compared with group I. Increased ORT from 19 to 21 degrees C to 24 degrees C resulted in an increased core temperature of at least 0.5 degrees C during living donor hepatectomy.

Hynson J, Sessler DI: Intraoperative warming therapies: A comparison of three devices. J Clin Anesth 4: 194-9

Article

May 1992
J CLIN ANESTH

To compare the effectiveness of three commonly used intraoperative warming devices. A randomized, prospective clinical trial. The surgical suite of a university medical center. Twenty adult patients undergoing kidney transplantation for end-stage renal disease. Patients were assigned to one of four warming therapy groups: circulating-water blanket (40 degrees C), heated humidifier (40 degrees C), forced-air warmer (43 degrees C, blanket covering legs), or control (no extra warming). Intravenous fluids were warmed (37 degrees C), and fresh gas flow was 5 L/min for all groups. No passive heat and moisture exchangers were used. The central temperature (tympanic membrane thermocouple) decreased approximately 1 degree C during the first hour of anesthesia in all groups. After three hours of anesthesia, the decrease in the tympanic membrane temperature from baseline (preinduction) was least in the forced-air warmer group (-0.5 degrees C +/- 0.4 degrees C), intermediate in the circulating-water blanket group (-1.2 degrees C +/- 0.4 degrees C), and greatest in the heated humidifier and control groups (-2.0 degrees C +/- 0.5 degrees C and -2.0 degrees C +/- 0.7 degrees C, respectively). Total cutaneous heat loss measured with distributed thermal flux transducers was approximately 35W (watts = joules/sec) less in the forced-air warmer group than in the others. Heat gain across the back from the circulating-water blanket was approximately 7W versus a loss of approximately 3W in patients lying on a standard foam mattress. The forced-air warmer applied to only a limited skin surface area transferred more heat and was clinically more effective (at maintaining central body temperature) than were the other devices. The characteristic early decrease in central temperature observed in all groups regardless of warming therapy is consistent with the theory of anesthetic-induced heat redistribution within the body.

Epidural versus General Anesthesia, Ambient Operating Room Temperature, and Patient Age as Predictors of Inadvertent Hypothermia

Article

Sep 1992

To elucidate the multifactorial nature of perioperative changes in body temperature, the influence of several clinical variables, including anesthetic technique, ambient operating room temperature, and age, were evaluated. Perioperative oral sublingual temperatures were measured in 97 patients undergoing lower extremity vascular surgery randomized to receive either general (GA) or epidural (EA) anesthesia. Surgery and anesthesia were performed in operating rooms (OR) with a relatively warm mean ambient temperature (24.5 +/- 0.4 degrees C) (GA, n = 30; EA, n = 33) or relatively cold mean ambient temperature (21.3 +/- 0.3 degrees C) (GA, n = 21; EA, n = 13). Patients were 35-94 yr old, with a mean age of 64.5 +/- 1.1 yr. A regression analysis was performed to determine the variables that correlated with intraoperative decrease in temperature and postoperative rewarming rate. The major correlates of greater intraoperative decrease in temperature were 1) GA (P = 0.003); 2) cold ambient OR temperature (P = 0.07); and 3) advancing patient age (P = 0.03). There was significant interaction between ambient OR temperature and type of anesthesia (P = 0.03): there was a greater intraoperative decrease in temperature with GA compared to EA in a cold OR but a similar decrease with GA and EA in a warm OR. The data also suggest an interaction between type of anesthesia and patient age (P = 0.06), showing a greater decrease in temperature with GA compared to EA in the younger patients, but a similar decrease between GA and EA in older patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Isoflurane Anesthesia and Circadian Temperature Cycles in Humans

Article

Jan 1992

Cognitive performance in postsurgical patients may be impaired by disturbances of normal circadian rhythm analogous to those produced by rapid transmeridian travel ("jet lag"). We therefore tested the hypothesis that isoflurane anesthesia alone produces a phase-delay in the human circadian temperature rhythm. We monitored central body temperature rhythms (using an ingested sensor) in five young, healthy, male volunteers at 3-min intervals for a total of 5 days. On the 3rd day, 3 h of 1.0% isoflurane anesthesia was administered beginning at approximately 10:00 AM. Thiopental, opioids, and other medications were not administered; volunteers were kept normothermic during anesthesia. Visual inspection of the data confirmed that periodicity of the temperature cycles remained near 24 h and that the curve was sinusoidal. Data were fit using a two-step sine and cosine regression for each 24-h period. Before anesthesia, volunteers demonstrated a consistent 24-h cycle, with a mean temperature (mesor) of 36.8 +/- 0.2 degrees C, amplitude of 0.8 +/- 0.2 degrees C, and time of maximum temperature (acrophase) of 3:06 PM +/- 2.4 h. Isoflurane anesthesia did not produce significant changes in the central temperature mesor. Peak-to-trough range (amplitude) of the temperature cycle was significantly reduced on the day of anesthesia (0.5 +/- 0.2 degrees C) but returned to normal on the subsequent day. Compared with the 2 days preceding isoflurane administration, there was no statistically significant change in acrophase on the day following anesthesia. These data do not support our hypothesis and suggest that the internal timer controlling circadian temperature cycles is resistant to clinical concentrations of isoflurane.

Perioperative Thermal Insulation

Article

Jun 1991

To determine the efficacy of passive insulators advocated for prevention of cutaneous heat loss, we determined heat loss in unanesthetized volunteers covered by one of the following: a cloth "split sheet" surgical drape; a Convertors disposable-paper split sheet; a Thermadrape disposable laparotomy sheet; an unheated Bair Hugger patient-warming blanket; 1.5-mil-thick plastic hamper bags; and a prewarmed, cotton hospital blanket. Cutaneous heat loss was measured using 10 area-weighted thermal flux transducers while volunteers were exposed to a 20.6 degrees C environment for 1 h. Heat loss decreased significantly from 100 +/- 3 W during the control periods to 69 +/- 6 W (average of all covers) after 1 h of treatment. Heat losses from volunteers insulated by the Thermadrape (61 +/- 6 W) and Bair Hugger covers (64 +/- 5 W) were significantly less than losses from those insulated by plastic bags (77 +/- 11 W). The paper drape (67 +/- 7 W) provided slightly, but not significantly, better insulation than the cloth drape (70 +/- 4 W). Coverage by prewarmed cotton blankets initially resulted in the least heat loss (58 +/- 8 W), but after 40 min, resulted in heat loss significantly greater than that for the Thermadrape (71 +/- 7 W). Regional heat loss was roughly proportional to surface area, and the distribution of regional heat loss remained similar with all covers. These data suggest that cost and convenience should be major factors when choosing among passive perioperative insulating covers. It is likely that the amount of skin surface covered is more important than the choice of skin region covered or the choice of insulating material.

Effect of bowel exposure on body temperature during surgical operations

Article

Aug 1971
AM J SURG

C.Francis Roe

Exposure of bowel causes increased evaporative heat loss which can, in experimental animals, cause a pronounced fall in body temperature. Return of the cold exposed bowel to the abdominal cavity causes a further fall in body temperature. These problems can be avoided by enclosing the bowel in a plastic envelope and irrigating the abdominal cavity with warm saline solution after the bowel has been returned to the abdominal cavity.

Influence of Ambient Temperature on Patient Temperature During Intraabdominal Surgery

Article

Mar 1971

ROGER H. MORRIS

The Effects of Ambient Temperature on Patient Temperature during Surgery Not Involving Body Cavities

Article

Mar 1970

Heat Flow and Distribution during Epidural Anesthesia

Article

Dec 1995

Core hypothermia after induction of epidural anesthesia results from both an internal core-to-peripheral redistribution of body heat and a net loss of heat to the environment. However, the relative contributions of each mechanism remain unknown. The authors thus evaluated regional body heat content and the extent to which core hypothermia after induction of anesthesia resulted from altered heat balance and internal heat redistribution. Twelve minimally clothed male volunteers were evaluated in a approximately 22 degrees C environment for 2.5 control hours before induction of epidural anesthesia and for 3 subsequent hours. Epidural anesthesia produced a bilateral sympathetic block in only six volunteers, and only their results are reported. Shivering, when observed, was treated with intravenous meperidine. Overall heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Arm and leg tissue heat contents were determined from 19 intramuscular needle thermocouples, 10 skin temperatures, and "deep" foot temperature. To separate the effects of redistribution and net heat loss, we multiplied the change in overall heat balance by body weight and the specific heat of humans. The resulting change in mean body temperature was subtracted from the change in esophageal or tympanic membrane (core) temperatures, leaving the core hypothermia specifically resulting from redistribution. Arm heat content decreased approximately 5 kcal/h after induction of anesthesia, but leg heat content increased markedly. Most of the increase in leg heat content was in the lower legs and feet. Core temperature increased slightly during the control period but decreased 0.8 +/- 0.3 degrees C in the 1st hour of anesthesia. Redistribution, contributing 89% to this initial decrease, required a net transfer of 20 kcal from the trunk to the extremities. During the subsequent 2 h of anesthesia, core temperature decreased an additional 0.4 +/- 0.3 degrees C, with redistribution contributing 62%. Thus, only 7 kcal were redistributed during the 2nd and 3rd hours of anesthesia. Redistribution therefore contributed 80% to the entire 1.2 +/- 0.3 degrees C decrease in core temperature during the 3 h of anesthesia. Core hypothermia during the 1st hour after induction of epidural anesthesia resulted largely from redistribution of body heat from the core thermal compartment to the distal legs. Even after 3 h of anesthesia, redistribution remained the major cause of core hypothermia. Despite the greater fractional contribution of redistribution during epidural anesthesia, core temperature decreased only half as much as during general anesthesia because metabolic rate was maintained and the arms remained vasoconstricted.

Heat Flow and Distribution during Induction of General Anesthesia

Article

Apr 1995

Core hypothermia after induction of general anesthesia results from an internal core-to-peripheral redistribution of body heat and a net loss of heat to the environment. However, the relative contributions of each mechanism remain unknown. The authors evaluated regional body heat content and the extent to which core hypothermia after induction of anesthesia resulted from altered heat balance and internal heat redistribution. Six minimally clothed male volunteers in an approximately 22 degrees C environment were evaluated for 2.5 control hours before induction of general anesthesia and for 3 subsequent hours. Overall heat balance was determined from the difference between cutaneous heat loss (thermal flux transducers) and metabolic heat production (oxygen consumption). Arm and leg tissue heat contents were determined from 19 intramuscular needle thermocouples, 10 skin temperatures, and "deep" foot temperature. To separate the effects of redistribution and net heat loss, we multiplied the change in overall heat balance by body weight and the specific heat of humans. The resulting change in mean body temperature was subtracted from the change in distal esophageal (core) temperature, leaving the core hypothermia specifically resulting from redistribution. Core temperature was nearly constant during the control period but decreased 1.6 +/- 0.3 degree C in the first hour of anesthesia. Redistribution contributed 81% to this initial decrease and required transfer of 46 kcal from the trunk to the extremities. During the subsequent 2 h of anesthesia, core temperature decreased an additional 1.1 +/- 0.3 degree C, with redistribution contributing only 43%. Thus, only 17 kcal was redistributed during the second and third hours of anesthesia. Redistribution therefore contributed 65% to the entire 2.8 +/- 0.5 degree C decrease in core temperature during the 3 h of anesthesia. Proximal extremity heat content decreased slightly after induction of anesthesia, but distal heat content increased markedly. The distal extremities thus contributed most to core cooling. Although the arms constituted only a fifth of extremity mass, redistribution increased arm heat content nearly as much as leg heat content. Distal extremity heat content increased approximately 40 kcal during the first hour of anesthesia and remained elevated for the duration of the study. The arms and legs are both important components of the peripheral thermal compartment, but distal segments contribute most. Core hypothermia during the first hour after induction resulted largely from redistribution of body heat, and redistribution remained the major cause even after 3 h of anesthesia.

Comparison of Forced-air Patient Warming Systems for Perioperative Use

Article

Mar 1994

Perianesthetic hypothermia is common and produces several complications, including postoperative shivering, decreased drug metabolism and clearance, and impaired wound healing. Forced-air warming transfers more than 50 W to the body and is an efficient method for either preventing or reversing decreases in core temperature. The authors compared the efficacy of four complete forced-air warming systems: (1) Bair Hugger 250/PACU Patient Warming System with 300 Warming Cover (Augustine Medical, Eden Prairie, MN); (2) Thermacare TC1000 Power Unit with TC1050 Comfort Quilt (Gaymar Industries, Orchard Park, NY); (3) WarmAir 130 Hypothermia System with 140 Warming Tube (Cincinnati Sub-Zero Products, Cincinnati, OH); and (4) WarmTouch 5000 Patient Warming System and 503-0810 CareQuilt (with the connecting hose compressed [short] and extended [long]) (Mallinckrodt Medical, St. Louis, MO). Six minimally clothed male volunteers were studied supine in a 24.5 degrees C environment. Cutaneous heat flux and skin temperature was measured at 14 area-weighted sites using thermal flux transducers. After 20-min control periods, volunteers were warmed for 40 min in each condition. A cotton blanket was placed over each cover. Power units were placed at the foot end of the bed, started cold, and set at maximum temperature and flow settings. All units reached maximum efficiency within 20 min. Total heat transfer with the Bair Hugger system (95 +/- 7 W) was greater (P < 0.05) than with WarmTouch (short hose 81 +/- 6 W and long hose 68 +/- 8 W), Thermacare (61 +/- 5 W), and WarmAir (38 +/- 6 W) systems. Each cover also was tested on a common power unit (Bair Hugger 200). Total heat transfer was greater (P < 0.05) with the Warming Cover (Bair Hugger) (88 +/- 8 W), followed by the Comfort Quilt (Thermacare) (56 +/- 6 W), CareQuilt (WarmTouch) (50 +/- 7 W), and the Warming Tube (WarmAir) (43 +/- 6 W). The advantages of the Bair Hugger system and Warming Cover are evident in areas that are important for heat transfer from the periphery to the body core (chest, axilla, abdomen, and upper legs).

The Effects of Preinduction Warming on Temperature and Blood Pressure during Propofol/Nitrous Oxide Anesthesia

Article

Sep 1993

Core temperature decreases rapidly after induction of anesthesia, largely because heat is redistributed to peripheral tissues. The hypothesis that warming peripheral tissues before induction of general anesthesia (prewarming) minimizes hypothermia was tested. Because circulating blood volume may be greater during exposure to heat compared to cold, the hypothesis that prewarming decreases the amount of hypotension associated with induction of anesthesia was tested also. Finally, the hypothesis that the difference between direct radial arterial blood pressure and blood pressure measured oscillometrically at the brachial artery depends on thermoregulatory and anesthetic conditions was tested. Each of six volunteers underwent general anesthesia (propofol and nitrous oxide) twice on the same day. Each anesthetic lasted 1 h and was preceded by either 2 h of active warming with forced air or 2 h of passive cooling by exposure to a typical operating room environment. After induction of each anesthetic, volunteers were fully exposed to the ambient environment. Volunteers recovered for 2 h before starting the second preinduction treatment. Initial tympanic membrane temperatures were similar before each preinduction treatment: 36.7 +/- 0.4 degrees C when volunteers were not warmed and 36.7 +/- 0.6 degrees C when volunteers were warmed. Tympanic membrane temperature did not change during the preinduction period without warming but increased slightly (delta T = 0.4 +/- 0.2 degree C) during warming. After induction of anesthesia, core temperatures decreased to 36.1 +/- 0.4 degree C over 1 h when volunteers were prewarmed but decreased to 34.9 +/- 0.4 degrees C when they were not. Radial arterial systolic, diastolic, and mean blood pressures were lower before induction of anesthesia when volunteers were warmed compared to when no warming was given. Oscillometric diastolic and mean pressures also were lower during prewarming; however, oscillometric systolic pressure did not differ significantly. Prewarming did not result in less hypotension after induction. Without warming, the difference (radial arterial minus oscillometric) in systolic blood pressure measurements was approximately 17 mmHg. Warming was associated with a reversal of the systolic pressure difference to approximately -6 mmHg. After induction of anesthesia, the differences in systolic and mean pressure measurements became more negative with respect to the preinduction values regardless of preinduction warming treatment. These data confirm our hypothesis that redistribution hypothermia can be minimized by preinduction warming of peripheral tissues. Prewarming decreases blood pressure but does not prevent subsequent hypotension after induction. The difference between radical arterial blood pressure and oscillometric blood pressure depends on thermoregulatory vasomotor changes but also may be influenced by vasodilation associated with administration of propofol and nitrous oxide.

Perioperative Normothermia to Reduce the Incidence of Surgical-Wound Infection and Shorten Hospitalization

Article

May 1996

Mild perioperative hypothermia, which is common during major surgery, may promote surgical-wound infection by triggering thermoregulatory vasoconstriction, which decreases subcutaneous oxygen tension. Reduced levels of oxygen in tissue impair oxidative killing by neutrophils and decrease the strength of the healing wound by reducing the deposition of collagen. Hypothermia also directly impairs immune function. We tested the hypothesis that hypothermia both increases susceptibility to surgical-wound infection and lengthens hospitalization. Two hundred patients undergoing colorectal surgery were randomly assigned to routine intraoperative thermal care (the hypothermia group) or additional warming (the normothermia group). The patient's anesthetic care was standardized, and they were all given cefamandole and metronidazole. In a double-blind protocol, their wounds were evaluated daily until discharge from the hospital and in the clinic after two weeks; wounds containing culture-positive pus were considered infected. The patients' surgeons remained unaware of the patients' group assignments. The mean (+/- SD) final intraoperative core temperature was 34.7 +/- 0.6 degrees C in the hypothermia group and 36.6 +/- 0.5 degrees C in the normothermia group (P < 0.001) Surgical-wound infections were found in 18 of 96 patients assigned to hypothermia (19 percent) but in only 6 of 104 patients assigned to normothermia (6 percent, P = 0.009). The sutures were removed one day later in the patients assigned to hypothermia than in those assigned to normothermia (P = 0.002), and the duration of hospitalization was prolonged by 2.6 days (approximately 20 percent) in hypothermia group (P = 0.01). Hypothermia itself may delay healing and predispose patients to wound infections. Maintaining normothermia intraoperatively is likely to decrease the incidence of infectious complications in patients undergoing colorectal resection and to shorten their hospitalizations.

Circadian changes in the sweating-to-vasoconstriction interthreshold range

Article

Feb 1998

Thermoregulatory defenses are characterized by thresholds, the core temperatures triggering each response. Core body temperature is normally maintained within the interthreshold range, temperatures between the sweating and vasoconstriction thresholds that do not trigger autonomic defenses. This range usually spans only some 0.2 degrees C, but it remains unknown whether similar precision is maintained during the circadian core temperature cycle of about 0.8 degrees C. Accordingly, we evaluated the interthreshold range at four times of the day. We studied ten male volunteers, each at 3 a.m., 8 a.m., 3 p.m., and 8 p.m. At least 12 h elapsed between tests, and the order was randomly assigned. At each study time, volunteers were warmed peripherally until sweating was observed. Skin temperature was subsequently kept constant while core temperature was decreased by central-venous infusion of ice-cold fluid until peripheral vasoconstriction was detected. The volunteers were not permitted to sleep during threshold determinations, although sleep was not otherwise controlled. The core temperature triggering an evaporative water loss of 40 g.m-2.h-1 identified the sweating threshold. Similarly, the vasoconstriction threshold was defined by the core temperature triggering the initial decreases in plethysmographic finger tip blood flow. The interthreshold range at 3 a.m. was twice that observed at the other study times (P<0.05). Our data suggest that autonomic control of body temperature is reduced at 3 a.m., even when sleep is denied. This result contradicts the general perception that circadian variation alters the thermoregulatory target temperature, but not precision of body temperature control.

Risk factors influencing inadvertent hypothermia in infants and neonates during anesthesia

Article

Aug 2005

The factors affecting the thermal status in neonates and infants undergoing general anesthesia are not yet investigated in detail. We evaluated the factors leading to intraoperative hypothermia in 60 neonates and infants. The initial body temperatures and the core temperatures at the 10th, 30th, 60th and 90th minute of anesthesia, as well as at the end of the operation were recorded. The patients were divided into the groups according to the age, type of surgery (minor vs major), operating room (OR) temperatures (low '<23 degrees C' vs high '>23 degrees C') and the initial core temperature of the patients. In 31 neonates and 29 infants, the mean core temperatures decreased 10 min after anesthesia induction. In all neonates and in infants with 'low OR temperature' (<23 degrees C), these decreases continued to the end of the surgery. Except infants undergoing minor surgery, in all patients, the core temperatures at the end of surgery were lower than the baseline temperature. The greatest decrease in core temperatures occurred in neonates undergoing major surgery and with low OR temperature. In low OR temperature, the decrease of core temperature is higher in patients with major surgery. In patients undergoing minor surgery, the decrease of core temperature is more in neonates than infants. Major surgery increased the chance of decrease of the core temperature by 2.66 times and operating room temperature less than 23 degrees C by 1.96 times. The type of surgery and the OR temperature are the main factors for decrease of the core temperature in neonates and infants. In neonates, the core temperatures are less stable, regardless of OR temperature and type of surgery. In high OR temperature, infants can stabilize their core temperature better than neonates.

Estimation of Mean Body Temperature from Mean Skin and Core Temperature

Article

Jan 2007

Mean body temperature (MBT) is the mass-weighted average temperature of body tissues. Core temperature is easy to measure, but direct measurement of peripheral tissue temperature is painful and risky and requires complex calculations. Alternatively MBT can be estimated from core and mean skin temperatures with a formula proposed by Burton in 1935: MBT = 0.64 x TCore + 0.36 x TSkin. This formula remains widely used, but has not been validated in the perioperative period and seems unlikely to remain accurate in dynamic perioperative conditions such as cardiopulmonary bypass. Therefore, the authors tested the hypothesis that MBT, as estimated with Burton's formula, poorly estimates measured MBT at a temperature range between 18 degrees and 36.5 degrees C. The authors reevaluated four of their previously published studies in which core and mass-weighted mean peripheral tissue temperatures were measured in patients undergoing substantial thermal perturbations. Peripheral compartment temperatures were estimated using fourth-order regression and integration over volume from 18 intramuscular needle thermocouples, 9 skin temperatures, and "deep" hand and foot temperature. MBT was determined from mass-weighted average of core and peripheral tissue temperatures and estimated from core temperature and mean skin temperature (15 area-weighted sites) using Burton's formula. Nine hundred thirteen data pairs from 44 study subjects were included in the analysis. Measured MBT ranged from 18 degrees to 36.5 degrees C. There was a remarkably good relation between measured and estimated MBT: MBTmeasured = 0.94 x MBTestimated + 2.15, r = 0.98. Differences between the estimated and measured values averaged -0.09 degrees +/- 0.42 degrees C. The authors concluded that estimation of MBT from mean skin and core temperatures is generally accurate and precise.

The Effects of Mild Perioperative Hypothermia on Blood Loss and Transfusion Requirement

Article

Feb 2008
ANESTHESIOLOGY

Anesthetic-induced hypothermia is known to reduce platelet function and impair enzymes of the coagulation cascade. The objective of this meta-analysis and systematic review was to evaluate the hypothesis that mild perioperative hypothermia increases surgical blood loss and transfusion requirement. The authors conducted a systematic search of published randomized trials that compared blood loss and/or transfusion requirements in normothermic and mildly hypothermic (34-36 degrees C) surgical patients. Results are expressed as a ratio of the means or relative risks and 95% confidence intervals (CI); P < 0.05 was considered statistically significant. Fourteen studies were included in analysis of blood loss, and 10 in the transfusion analysis. The median (quartiles) temperature difference between the normothermic and hypothermic patients among studies was 0.85 degrees C (0.60 degrees C versus 1.1 degrees C). The ratio of geometric means of total blood loss in the normothermic and hypothermic patients was 0.84 (0.74 versus 0.96), P = 0.009. Normothermia also reduced transfusion requirement, with an overall estimated relative risk of 0.78 (95% CI 0.63, 0.97), P = 0.027. Even mild hypothermia (<1 degree C) significantly increases blood loss by approximately 16% (4-26%) and increases the relative risk for transfusion by approximately 22% (3-37%). Maintaining perioperative normothermia reduces blood loss and transfusion requirement by clinically important amounts.

Skin-surface warming: Heat flux and central temperature.

Jan 1990
218

Isoflurane-induced vasodilation minimally increases cutaneous heat loss.

Jan 1991
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Postoperative hemodynamic and thermoregulatory consequences of intraoperative core hypothermia.

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Pre-induction skin-surface warming minimizes intraoperative core hypothermia.

Jan 1995
384

Effects of Ambient Temperature and Forced-air Warming on Intraoperative Core Temperature: A Factorial Randomized Trial

Abstract

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