Mild hypothermia alters propofol pharmacokinetics and increases the duration of action of atracurium

The relationship between intraoperative hypothermia and the ccurrence of surgical site infections: a meta-analysis of observational studies

Objective

Inconsistent evidence exists regarding the association between intraoperative hypothermia and incidence of surgical site infection (SSI). This study aimed to determine the association between intraoperative hypothermia and SSI.

Materials and methods

A systematic review was conducted using Embase, PubMed, and Web of Science to identify observational studies evaluating the risk of SSI in patients with intraoperative hypothermia. The primary outcome measure was the diagnosis of SSI within 30 days of surgery. The pooled risk ratio was estimated using a fixed- or random-effect meta-analysis. Sensitivity analyses were performed to examine the impact of the structural design of preoperative warming on the pooled risk of SSI.

Results

Five studies representing 6,002 patients were included in the present meta-analysis. Intraoperative hypothermia was not associated with SSI risk in patients (HR = 1.22, 95% CI: 0.95-2.24, P = 0.119). The pooled hazard ratio showed that intraoperative hypothermia did not result in a higher risk of SSI.

Conclusions

Intraoperative hypothermia was not associated with the risk of SSI. Further studies using objective exposure measurements are required to confirm these results.

Burning Question: How Does Our Brain Process Positive and Negative Cues Associated with Thermosensation?

Whether it is the dramatic suffocating sensation from a heat wave in the summer or the positive reinforcement arising from a hot drink on a cold day; we can certainly agree that our thermal environment underlies our daily rhythms of sensation. Extensive research has focused on deciphering the central circuits responsible for conveying the impact of thermogenesis on mammalian behavior. Here, we revise the recent literature responsible for defining the behavioral correlates that arise from thermogenic fluctuations in mammals. We transition from the physiological significance of thermosensation to the circuitry responsible for the autonomic or behavioral responses associated with it. Subsequently, we delve into the positive and negative valence encoded by thermoregulatory processes. Importantly, we emphasize the crucial junctures where reward, pain, and thermoregulation intersect, unveiling a complex interplay within these neural circuits. Finally, we briefly outline fundamental questions that are pending to be addressed in the field. Fully deciphering the thermoregulatory circuitry in mammals will have far-reaching medical implications. For instance, it may lead to the identification of novel targets to overcome thermal pain or allow the maintenance of our core temperature in prolonged surgeries.

Comparative Efficacy of Six Active Warming Systems for Intraoperative Warming in Adult Patients Undergoing Laparoscopic Surgery: A Systematic Review and Network Meta-Analysis

Intraoperative hypothermia is very common and harmful in adult patients undergoing laparoscopic surgery. A variety of active warming systems has received close attention and has been researched by related scholars. However, the relative efficacy of these systems and which active warming system is preferred for such patients remain unclear. The aim of this study was to compare and rank six active warming systems regarding intraoperative warming efficacy in adult patients undergoing laparoscopic surgery. Following the PRISMA 2020 guidelines, relevant randomized controlled trials (RCTs) on the efficacy of different active warming systems in warming adult patients undergoing laparoscopic surgery were searched from five English databases and three Chinese databases. The quality of the studies was assessed using the Cochrane Risk of Bias tool (RoB2). The outcome was the final intraoperative core temperature. We estimated direct effects by using pairwise meta-analysis, estimated relative effects and ranking with the consistency model to conduct an NetworkMeta-Analysis (NMA). We used GRADE (Grading of Recommendations Assessment, Development, and Evaluation) to assess the certainty of the evidence. Sensitivity analysis was performed to test the robustness of the results. This study is registered with PROSPERO, with number CRD42022309057. In total, 19 RCTs involving 6 active warming systems and comprising 1364 patients were included in this NMA. The NMA once again confirmed the validity of forced-air warming (FAW) systems compared with other active warming systems, and further showed that underbody FAW was associated with more remarkable warming efficacy in different types of FAW systems. NMA was used to perform an exhaustive comparison of the warming efficacy of six active warming systems and indicated that underbody FAW was most likely to be the most effective warming system in adult patients undergoing laparoscopic surgery; however, considering the sparsity of the network, our results should be cautiously interpreted. Furthermore, a large number of high-quality RCTs comparing the warming efficacy of different competitive active warming systems are needed.

The Effects of Active Warming on Core Body Temperature and Thermal Comfort in Patients After Transurethral Resection of the Prostate: A Randomized Clinical Trial

Prevention and treatment of hypothermia by active warming in perioperative period care is recommended but scientific evidence of its effectiveness in a clinical setting is scarce. The purpose of this study was to determine the effects of warmed intravenous fluids (WIVF) on the core body temperature and the patients' thermal comfort. Baseline data of 105 male patients undergoing TUR-P surgery and bladder irrigation were analyzed. The experimental group was warmed using active WIVF, and the control group's routine care was conducted using a cotton blanket. Body temperature was higher in patients in the experimental group than those in the control group. Repeated measures Manova revealed significantly different core temperature changes between groups (F = 34.446, p = .001). The thermal comfort scores were also higher in the experimental group than in the control group (x² = 203.552, p = .001). The findings indicated that WIVF can enhance body temperature and improve the thermal comfort of patients.

Risk factors for pulmonary complications after laparoscopic liver resection: a multicenter retrospective analysis

BACKGROUND

Postoperative pulmonary complications (PPCs) are among the most common complications after liver resection. Although the application of laparoscopy has reduced the incidence of PPCs, the rate of PPCs after laparoscopic liver resection (LLR) remains high and the risk factors for the same are unclear. Therefore, this study aimed to determine the risk factors for PPCs after LLR.

METHODS

In this multicenter study, 296 patients underwent LLR from January 2019 to December 2020. Demographic data, pathological variables, and perioperative variables were reviewed. Univariate and multivariate analyses were performed to identify the independent risk factors for PPCs.

RESULTS

Of the 296 patients, 80 (27.0%) developed PPCs. Patients with PPCs had significantly increased total costs, operation costs, length of stays, and postoperative hospital stays. Multivariate analysis identified three independent risk factors for PPCs after LLR: smoking [Odds ratio (OR): 5.413, 95% confidence intervals (CI): 2.446-11.978, P =  < 0.001], location of lesion in segment 7 or 8 (OR 3.134, 95% CI 1.593-6.166, P = 0.001), duration of liver ischemia (OR 1.038, 95% CI 1.022-1.054, P < 0.001), and presence of intraoperative hypothermia (OR 3.134, 95% CI 1.593-6.166, P < 0.001).

CONCLUSION

Smoking, location of lesion in segment 7 or 8, duration of liver ischemia and intraoperative hypothermia were independent risk factors for PPCs which significantly increased the length of stays and burden of healthcare costs.

Nonconvulsive status epilepticus following cardiac arrest: overlooked, untreated and misjudged

AIMS

Seizures and status epilepticus (SE) are detected in almost a third of the comatose cardiac arrest survivors. As the literature is quite exhaustive regarding SE with motor symptoms in those patients, little is known about nonconvulsive SE (NCSE). Our aim was to compile the evidence from the literature of the frequency and outcome of NCSE in adult patients remaining in coma after resuscitation.

METHODS

The medical search PubMed was screened for most relevant articles reporting the emergence and outcome of NCSE in comatose post-resuscitated adult patients.

RESULTS

We identified 11 cohort studies (four prospective observational, seven retrospective) including 1092 patients with SE in 29-96% and NCSE reported in 1-20%. EEG evaluation started at a median of 9.5 h (range 7.5-14.8) after cardiac arrest, during sedation and targeted temperature management (TTM). Favorable outcome after NCSE occurred in 24.5%. We found no study reporting EEG to detect or exclude NCSE in patients remaining in coma prior to the initiation of TTM and without sedation withing the first hours after ROSC.

DISCUSSION

Studies on NCSE after ROSC are scarce and unsystematic, reporting favorable outcome in every fourth patient experiencing NCSE after ROSC. This suggests that NCSE is often overlooked and outcome after NCSE is not always poor. The low data quality does not allow firm conclusions regarding the effects of NCSE on outcome calling for further investigation. In the meantime, clinicians should avoid equating NCSE after ROSC with poor prognosis.

Nonconvulsive status epilepticus following cardiac arrest—are we missing the beginning?

Background

Status epilepticus (SE) is a common complication in patients surviving a cardiac arrest, but little is known about the frequency of nonconvulsive status epilepticus (NCSE).

Objectives

To compile the first the evidence from the literature of the overall frequency of NCSE in adults with persistent coma following cardiac arrest. Secondarily, to assess the emergence of NCSE in comatose resuscitated patients within the first hours of the return of spontaneous circulation (ROSC) and before inducing target temperature management.

Material and methods

The medical search engine PubMed was screened to identify prospective and retrospective studies in English reporting on the frequency of NCSE in comatose post-resuscitated patients. Study design, time of EEG performance, detection of SE and NCSE, outcomes, and targeted temperature management were assessed.

Results

Only three cohort studies (one prospective and two retrospective) reported on the EEG evaluation describing NCSE during ongoing sedation and target temperature management. Overall, we identified 213 patients with SE in 18–38% and NCSE in 5–12%. Our review found no study reporting NCSE in resuscitated adult patients remaining in coma within the first hours of ROSC and prior to targeted temperature management and sedation.

Conclusion

Studies of NCSE after ROSC in adults are rare and mostly nonsystematic. This and the low proportion of patients reported having NCSE following ROSC suggest that NCSE before target temperature management and sedation is often overlooked. The limited quality of the data does not allow firm conclusions to be drawn regarding the effects of NCSE on outcome calling for further investigations. Clinicians should suspect NCSE in patients with persistent coma before starting sedation and targeted temperature management.

Efficacy and safety of remimazolam besylate in bronchoscopy for adults: A multicenter, randomized, double-blind, positive-controlled clinical study

Background: With the development of fiberoptic bronchoscopy in the diagnosis and treatment of various pulmonary diseases, the anesthesia/sedation requirements are becoming more demanding, posing great challenges for patient safety while ensuring a smooth examination/surgery process. Remimazolam, a brand-new ultra-short-acting anesthetic, may compensate for the shortcomings of current anesthetic/sedation strategies in bronchoscopy.

Methods: This study was a prospective, multicenter, randomized, double-blind, parallel positive controlled phase 3 clinical trial. Subjects were randomized to receive 0.2 mg/kg remimazolam besylate or 2 mg/kg propofol during bronchoscopy to evaluate the efficacy and safety of remimazolam.

Results: A total of 154 subjects were successfully sedated in both the remimazolam group and the propofol group, with a success rate of 99.4% (95%CI of the adjusted difference −6.7 × 10%–6% to −5.1 × 10%–6%). The sedative effect of remimazolam was noninferior to that of propofol based on the prespecified noninferiority margin of −5%. Compared with the propofol group, the time of loss of consciousness in the remimazolam group (median 61 vs. 48s, p < 0.001), the time from the end of study drug administration to complete awakening (median 17.60 vs. 12.80 min, p < 0.001), the time from the end of bronchoscopy to complete awakening (median 11.00 vs. 7.00 min, p < 0.001), the time from the end of study drug administration to removal of monitoring (median 19.50 vs. 14.50 min, p < 0.001), and the time from the end of bronchoscopy to removal of monitoring (median 12.70 vs. 8.60 min, p < 0.001) were slightly longer. The incidence of Adverse Events in the remimazolam group and the propofol group (74.8% vs. 77.4%, p = 0.59) was not statistically significant, and none of them had Serious Adverse Events. The incidence of hypotension (13.5% vs. 29.7%, p < 0.001), hypotension requiring treatment (1.9% vs. 7.7%, p = 0.017), and injection pain (0.6% vs. 16.8%, p < 0.001) were significantly lower in the remimazolam group than in the propofol group.

Conclusion: Moderate sedation with 0.2 mg/kg remimazolam besylate is effective and safe during bronchoscopy. The incidence of hypotension and injection pain was less than with propofol, but the time to loss of consciousness and recovery were slightly longer.

Clinical Trial Registration:clinicaltrials.gov, ChiCTR2000039753

The Impact of Low Cardiac Output on Propofol Pharmacokinetics across Age Groups-An Investigation Using Physiologically Based Pharmacokinetic Modelling

BACKGROUND

pathophysiological changes such as low cardiac output (LCO) impact pharmacokinetics, but its extent may be different throughout pediatrics compared to adults. Physiologically based pharmacokinetic (PBPK) modelling enables further exploration.

METHODS

A validated propofol model was used to simulate the impact of LCO on propofol clearance across age groups using the PBPK platform, Simcyp^® (version 19). The hepatic and renal extraction ratio of propofol was then determined in all age groups. Subsequently, manual infusion dose explorations were conducted under LCO conditions, targeting a 3 µg/mL (80-125%) propofol concentration range.

RESULTS

Both hepatic and renal extraction ratios increased from neonates, infants, children to adolescents and adults. The relative change in clearance following CO reductions increased with age, with the least impact of LCO in neonates. The predicted concentration remained within the 3 µg/mL (80-125%) range under normal CO and LCO (up to 30%) conditions in all age groups. When CO was reduced by 40-50%, a dose reduction of 15% is warranted in neonates, infants and children, and 25% in adolescents and adults.

CONCLUSIONS

PBPK-driven, the impact of reduced CO on propofol clearance is predicted to be age-dependent, and proportionally greater in adults. Consequently, age group-specific dose reductions for propofol are required in LCO conditions.

Clinical Survey of Current Perioperative Body Temperature Management: What Major Factors Influence Effective Hypothermia Prevention Practice?

Purpose

Inadvertent intraoperative hypothermia (IIH) is generally associated with several postoperative complications. Inspite of the existing guidelines, the global incidence of IIH remains unacceptably high. Understanding the conditions that influence temperature management is critical for developing future interventions to improve the postoperative patient outcomes. This study aimed to identify the major factors that hinder the implementation of IIH prevention practices.

Methods

Through a literature research, pilot small-sample investigation, and expert suggestions, 11 factors that may hinder the implementation of IIH prevention practices were identified. A questionnaire was developed, and each question was used to assess each factor. After approval by the Research Ethics Board, the questionnaires were sent to the staff anaesthesiologists at two academic hospitals via WeChat. Each answer was coded according to the degree to which the factor was affected, as anticipated. Finally, the answers were analysed based on the 80/20 rule to identify the major barriers to effective temperature management.

Results

We included 195 participants. Knowledge, memory, attention and decision processes, beliefs about consequences, and environmental context and resources were the major factors, with cumulative composition ratios of 24%, 43.4%, 57.7%, and 70.7%, respectively. Meanwhile, behavioural regulation and social influence were the secondary factors, with cumulative composition ratios of 80.4% and 87.5%, respectively. Reinforcement, confidence in capacity, duty realisation, skills, and intention were the general factors with cumulative composition ratios of 94.3%, 99.8%, 100%, 100%, and 100%, respectively.

Conclusion

Four factors-knowledge, memory, attention and decision process, beliefs about consequences, and environmental context and resources-were the major factors that influence the effective hypothermia prevention practice.

Relevance to Clinical Practice

These major factors will be used in further studies as a basis to develop the corresponding solutions and improve the patient outcomes in clinical practice.

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

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.

Perioperative hypothermia in open and laparoscopic colorectal surgery

BACKGROUND

The consequences of even mild inadvertent perioperative hypothermia (IPH) are significant. There is a perception laparoscopic abdominal surgery is less prone to cause hypothermia than open surgery. However, during laparoscopic surgery, the peritoneal cavity is insufflated with carbon dioxide, which has a greater evaporative capacity than ambient air. This study compared the intra-operative temperature profile of patients undergoing open and laparoscopic colorectal surgery to define the incidence and severity of hypothermia.

METHODS

All adult patients undergoing colorectal surgery between May 2005 and August 2013 were identified from an electronic database. Cases were categorized into laparoscopic and open cases. Hypothermic episodes were defined as a temperature less than 36°C lasting for more than two consecutive minutes. The incidence of hypothermic episodes, the total time under 36°C and the area under the curve (degree-minutes) were calculated.

RESULTS

A total of 1547 cases were analysed. The overall incidence of hypothermia was 67.0%. The incidence of cases with a hypothermic episode was greater in the laparoscopic group compared to the open group (71.23% versus 63.16%; chi-squared P-value 0.001). However, when other factors were considered, there was no significant difference in the relative risk of a hypothermic episode between types of surgery. There were significant differences in the severity of hypothermia.

CONCLUSION

Despite current measures to reduce the incidence, IPH remains a significant problem in colorectal surgery irrespective of the surgical approach. Further research is required to better characterize techniques that can reduce its incidence.

Comparison of zero heat flux and double sensor thermometers during spinal anaesthesia: a prospective observational study

Because of the difficulties involved in the invasive monitoring of conscious patients, core temperature monitoring is frequently neglected during neuraxial anaesthesia. Zero heat flux (ZHF) and double sensor (DS) are non-invasive methods that measure core temperature from the forehead skin. Here, we compare these methods in patients under spinal anaesthesia. Sixty patients scheduled for elective unilateral knee arthroplasty were recruited and divided into two groups. Of these, thirty patients were fitted with bilateral ZHF sensors (ZHF group), and thirty patients were fitted with both a ZHF sensor and a DS sensor (DS group). Temperatures were saved at 5-min intervals from the beginning of prewarming up to one hour postoperatively. Bland–Altman analysis for repeated measurements was performed and a proportion of differences within 0.5 °C was calculated as well as Lin`s concordance correlation coefficient (LCCC). A total of 1261 and 1129 measurement pairs were obtained. The mean difference between ZHF sensors was 0.05 °C with 95% limits of agreement − 0.36 to 0.47 °C, 99% of the readings were within 0.5 °C and LCCC was 0.88. The mean difference between ZHF and DS sensors was 0.33 °C with 95% limits of agreement − 0.55 to 1.21 °C, 66% of readings were within 0.5 °C and LCCC was 0.59. Bilaterally measured ZHF temperatures were almost identical. DS temperatures were mostly lower than ZHF temperatures. The mean difference between ZHF and DS temperatures increased when the core temperature decreased.

Trial registration: The study was registered in ClinicalTrials.gov on 13th May 2019, Code NCT03408197.

The Use of Neuromuscular Blockers to Prevent Shivering in the Setting of Postcardiac Arrest Targeted Temperature Management: A Narrative Review of an Off-Label Indication

Targeted temperature management (TTM) has become a standard of care over the past two decades for the improvement in neurologic function and mortality in postcardiac arrest patients. There are various mechanisms by which hypothermia helps to improve these outcomes, one of which is by reducing oxygen requirements. Less established is the use of nondepolarizing neuromuscular blockers (NMBs) to prevent shivering during TTM. Shivering can be disadvantageous in this setting as it increases oxygen requirements, which TTM is actively trying to decrease, in an already oxygen-deprived system as well as generates heat making it difficult to maintain hypothermia. Whether NMBs can improve these outcomes is conflicting in the currently available literature and there lacks a consensus on their role in shivering management. The pharmacokinetic and pharmacodynamic responses of these agents may be altered in hypothermic patients, therefore, their standard of monitoring may be unreliable. The accurate dosing and administration of these agents also remain unclear, further complicated by the lack of a standard use protocol. Various studies have been conducted regarding the use of NMBs to prevent shivering in postcardiac arrest patients undergoing TTM; however, it remains an off-label indication requiring further investigation.

Full title: The prevalence of and predictors for perioperative hypothermia in postanaesthesia care unit

BACKGROUND

Hypothermia is a common clinical issue during the perioperative period. The patients with perioperative inadvertent hypothermia are associated with higher risk of postoperative complications and higher hospitalisation costs.

AIMS

The aim of this study is to explore the prevalence of and predictors for hypothermia in patients entering postanaesthesia care unit.

DESIGN

Retrospective cohort study.

METHODS

A rigorous retrospective cohort study was conducted according to the STROBE reporting checklist. A total of 7216 patients were enrolled in this study. The perioperative variables potentially related to hypothermia were collected. Univariate analysis and multivariate logistic regression analysis were performed to investigate the contributing factors.

RESULTS

The overall prevalence of inadvertent hypothermia in postanaesthesia care unit was 21.3% (n = 1505). The multivariate logistic regression analysis showed that age >65 (OR = 1.561, 95% CI 1.371-1.778, p < .001), non-supine position [lateral decubitus position (OR = 1.341, 95% CI 1.133-1.586, p = .001), lithotomy position (OR = 1.639, 95% CI 1.295-2.075, p < .001)], non-superficial surgery (OR = 2.195, 95% CI 1.566-3.077, p < .001), non-open surgery [laparoscopic surgery (OR = 1.205, 95% CI 1.020-1.423, p = .029), endoscopic surgery (OR = 1.430, 95%CI 1.084-1.887, p = .011)], the volume of intravenous infusion fluid >1000 ml (OR = 1.814, 95% CI 1.500-2.194, p < .001), blood transfusion (OR = 1.552, 95% CI 1.159-2.078, p = .003), operation performed in the summer or fall (OR = 1.874, 95%CI 1.656-2.122, p < .001) and use of dexmedetomidine (OR = 1.147, 95%CI 1.015-1.296, p = .028) were associated with increased risk of hypothermia. In contrast, our finding showed that body mass index ≥25 kg/m² (OR = 0.556, 95%CI 0.491-0.630, p < .001), higher baseline body temperature (OR = 0.641, 95%CI 0.541-0.761, p < .001) and duration of fasting ≥18 h (OR = 0.487, 95%CI 0.345-0.689, p < .001) were associated with decreased risk of hypothermia. Compared with non-hypothermic patients, patients with hypothermia were associated with prolonged length of hospital days (5 vs. 4 days, p < .001).

CONCLUSION

For patients admitted to postanaesthesia care unit after elective procedures, old age, non-supine position, non-open surgery, non-superficial surgery, large volume of intravenous infusion fluid, dexmedetomidine, blood transfusion and Summer or Fall operative season were associated with increased risk of hypothermia, whereas high body mass index, high baseline body temperature and long fasting duration were associated with decreased risk of hypothermia.

RELEVANCE TO CLINICAL PRACTICE

The outcomes of this study will raise the concerns of perioperative care team on hypothermia in surgical patients. Measures should be taken to improve perioperative hypothermia and clinical outcome.

Clinical evaluation of a cutaneous zero-heat-flux thermometer during cardiac surgery

We evaluated the disposable non-invasive SpotOn™ thermometer relying on the zero-heat-flux technology. We tested the hypothesis that this technology may accurately estimate the core temperature. The primary objective was to compare cutaneous temperature measurements from this device with blood temperatures measured with the pulmonary artery catheter. Secondary objective was to compare measurements from the zero-heat-flux thermometer indirectly with other routinely used thermometers (nasopharyngeal, bladder, rectal). We included 40 patients electively scheduled for either off-pump coronary artery bypass surgery or pulmonary thromboendarterectomy. Temperatures were measured using zero-heat-flux (SpotOn™), pulmonary artery catheter, nasopharyngeal, rectal, and bladder thermometers. Agreement was assessed using the Bland and Altman random effects method for repeated measures data, and Lin's concordance correlation coefficient. Accuracy was estimated (defined as <0.5° difference with the gold standard), with a 95% confidence interval considering the multiple pairs of measurements per patient. 17 850 sets of temperature measurements were analyzed from 40 patients. The mean overall difference between zero-heat-flux and pulmonary artery catheter thermometer was -0.06 °C (95% limits of agreement of ± 0.89 °C). In addition, 14 968 sets of temperature measurements were analyzed from 34 patients with all thermometers in situ. Results from the zero-heat-flux thermometer showed better agreement with the pulmonary artery catheter than the other secondary core thermometers assessed. In conclusion, the SpotOn™ thermometer reliably assessed core temperature during cardiac surgery. It could be considered an alternative for other secondary thermometers in the assessment of core temperature during general anesthesia.

Volatile Versus Intravenous Anesthetics in Cardiac Anesthesia: a Narrative Review

Purpose of the Review

The present review addresses clinicians and gives an overview about the experimental rationale for pharmacological conditioning associated with volatile anesthetics, opioids, and propofol; the current clinical data; and the technical considerations regarding the clinical routine in cardiac anesthesia.

Recent Findings

Volatile anesthetics have been standard of care for general anesthesia for cardiac surgery, especially while using cardiopulmonary bypass. The 2019 published MYRIAD trial was not able to show a difference in mortality or cardiac biomarkers for volatile anesthetics compared to total intravenous anesthesia (TIVA), raising the question of equivalence with respect to patient outcome.

Summary

Reviewing the literature, the scientific foundation for the belief of clinically relevant conditioning by uninterrupted administration of a volatile anesthetic is weak. TIVA can also be performed safely in patients undergoing cardiac surgery.

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

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 that a forced-air warming (FAW) unit connected to the thermal suit is superior to a commercial FAW 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 FAW 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 = .4) or on admission to the recovery room (P = .07). One patient in the Thermal suit group (5%) vs six patients in the Hospital clothes group (32%) suffered from intraoperative hypothermia (P = .04, 95% CI 1.9%-49%). Mean skin temperatures (MSTs) 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 FAW unit was not superior to a commercial FAW blanket, although the incidence of intraoperative hypothermia was lower in patients treated with a thermal suit.

Protocol Implementation for Normothermia in Surgery Settings in Italy: Budget-Impact Analysis

Introduction

Hypothermia is a well-known risk of the perioperative period and considered a preventable effect of anesthesia care. Nevertheless, it is not fully controlled, causing a number of adverse outcomes following surgical operations and thus increasing length of stay in hospital and treatment costs. The aim of this study was to assess the budget impact (BI) of the implementation of proactive strategies to prevent inadvertent perioperative hypothermia (IPH) in surgical patients in Italy, as recommended by international guidelines and by a good clinical practice (GCP) guideline of the Italian Society of Anesthesia, Analgesia, Reanimation, and Intensive Care.

Methods

BI was calculated over a 3-year period from the perspective of the Italian National Health Service (NHS). Model inputs were extracted from national literature when available and otherwise from international sources. The reference analytic model was based on the cost-effectiveness analysis of the National Institute for Health and Care Excellence clinical guidance 65. Estimates were based on assessments made about current malpractice in Italy and on a hypothesis of how future practice might change by implementing the GCP. Model output included overall BI results, variations in the number of warmed patients, medical-device average costs and use of mix.

Results

The base-case estimate quantified a decrease of 35% in extra days of hospital stay due to IPH and a net BI of –€60.92 million.

Conclusion

Increasing protocol adoption for preventing IPH would lead to both clinical advantages and significant savings for the NHS. Its large diffusion in Italian hospitals is thus desirable.

Perioperative Temperature Management in Children: What Matters?

Inadvertent perioperative hypothermia is common and associated with increased risk of perioperative complications. Adult data drives most guidelines for pediatric perioperative temperature management and does not consistently demonstrate effectiveness in children. This study aims to identify risk factors for hypothermia and determine the effectiveness of current interventions in the pediatric population.

METHODS

We carried out a prospective observational study in children undergoing anesthesia in our tertiary pediatric unit. We included 869 patients (<16 y) undergoing emergency/elective surgeries over 2 months. Our team recorded the incidence of hypothermia (tympanic core temperature < 36°C) within 15 minutes of arrival to the postanesthetic care unit. We collected data such as patient demographic, surgical, anesthetic (including monitoring and warming measures used), and operating theater (OT) temperature. We performed statistical analysis to identify risk factors associated with hypothermia.

RESULTS

Postoperative hypothermia incidence was 12.3% (107/869). The mean core temperature on arrival to the postanesthetic care unit was 36.6°C (+SD 0.45) in normothermic patients versus 35.6°C (+SD 0.34) in hypothermic patients. Multivariable analysis identified starting ambient OT temperature [odds ratio (OR) = 0.83, confidence interval (CI): 0.71-0.96; P = 0.010], intraoperative temperature monitoring (OR = 0.49, CI: 0.28-085; P = 0.011), use of occlusive dressing (OR = 0.35, CI: 0.15-0.85; P = 0.020), and active forced-air warming (OR = 0.42, CI: 0.25-0.70; P = 0.001) as factors independently protective of postoperative hypothermia. Hypothermia occurred less frequently with emergency vs. elective procedures (OR 0.43, CI: 0.21-0.91; P = 0.026).

CONCLUSIONS

Routine core temperature monitoring and active forced-air warming are useful measures to prevent hypothermia. Additionally, occlusive covers and controlling ambient OT temperature are cost-effective and safe methods to reduce inadvertent hypothermia.

The effect of interscalene brachial plexus block with propofol sedation on preventing perioperative hypothermia during arthroscopic shoulder surgery

Background

Interscalene brachial plexus block (ISBPB) is commonly used with general anesthesia for postoperative pain management in shoulder surgery. This study investigated the incidence of hypothermia and changes in the body temperature in patients undergoing arthroscopic shoulder surgery under ISBPB with propofol sedation.

Methods

This retrospective study enrolled 220 patients who underwent arthroscopic shoulder surgery. Patients were divided into general anesthesia (n = 34) and ISBPB with propofol sedation (n = 186) groups, and medical records were retrospectively compared. In addition, patients from the ISBPB group were further divided according to age (elderly [≥ 65 years], n = 98 vs. young [< 65 years], n = 88), and the incidence of hypothermia and changes in the body temperature were compared.

Results

Twenty-seven patients (12.3%) experienced perioperative hypothermia (range: 35.3–35.9℃). The incidence of perioperative hypothermia was 29.4% and 9.1% in the general anesthesia and ISBPB groups, respectively, and there was a significant difference between the two groups (P = 0.002). The incidence of perioperative hypothermia according to age in the ISBPB group was 9.2% and 9.1% in the elderly and young groups, respectively, and there was no significant difference between the two groups (P = 0.983).

Conclusions

The incidence of perioperative hypothermia during arthroscopic shoulder surgery under ISBPB with propofol sedation is lower than that under general anesthesia. Furthermore, when using ISBPB with propofol sedation, the incidence of perioperative hypothermia in elderly patients is similar to that in younger patients.

In the ICU - delirium post cardiac arrest

PURPOSE OF REVIEW

The present review aims to describe the clinical impact and assessment tools capable of identifying delirium in cardiac arrest survivors and providing strategies aimed at preventing and treating delirium.

RECENT FINDINGS

Patient factors leading to a cardiac arrest, initial resuscitation efforts, and postresuscitation management all influence the potential for recovery and the risk for development of delirium. Data suggest that delirium in cardiac arrest survivors is an independent risk factor for morbidity and mortality. Recognizing delirium in postcardiac arrest patients can be challenging; however, detection is not only achievable, but important as it may aid in predicting adverse outcomes. Serial neurologic examinations and delirium assessments, targeting light sedation when possible, limiting psychoactive medications, and initiating patient care bundles are important care aspects for not only allowing early identification of primary and secondary brain injury, but in improving patient morbidity and mortality.

SUMMARY

Developing delirium after cardiac arrest is associated with increased morbidity and mortality. The importance of addressing modifiable risk factors, recognizing symptoms early, and initiating coordinated treatment strategies can help to improve outcomes within this high risk population.

The Influence of Therapeutics on Prognostication After Cardiac Arrest

PURPOSE OF REVIEW

The goal of this review is to highlight the influence of therapeutic maneuvers on neuro-prognostication measures administered to comatose survivors of cardiac arrest. We focus on the effect of sedation regimens in the setting of targeted temperature management (TTM), one of the principle interventions known to improve neurological recovery after cardiac arrest. Further, we discuss the critical need for novel markers, as well as refinement of existing markers, among patients receiving extracorporeal membrane oxygenation (ECMO) in the setting of failed conventional resuscitation, known as extracorporeal cardiopulmonary resuscitation (ECPR).

RECENT FINDINGS

Automated pupillometry may have some advantage over standard pupillary examination for prognostication following TTM, sedation, or the use of ECMO after cardiac arrest. New serum biomarkers such as Neurofilament light chain have shown good predictive abilities and need further validation in these populations. There is a high-level uncertainty in brain death declaration protocols particularly related to apnea testing and appropriate ancillary tests in patients receiving ECMO. Both sedation and TTM alone and in combination have been shown to affect prognostic markers to varying degrees. The optimal approach to analog-sedation is unknown, and requires further study. Moreover, validation of known prognostic markers, as well as brain death declaration processes in patients receiving ECMO is warranted. Data on the effects of TTM, sedation, and ECMO on biomarkers (e.g., neuron-specific enolase) and electrophysiology measures (e.g., somatosensory-evoked potentials) is sparse. The best approach may be one customized to the individual patient, a precision-medicine approach.

Causal Analysis of World Health Organization's Surgical Safety Checklist Implementation Quality and Impact on Care Processes and Patient Outcomes: Secondary Analysis From a Large Stepped Wedge Cluster Randomized Controlled Trial in Norway

Supplemental Digital Content is available in the text

Objective:

We hypothesize that high-quality implementation of the World Health Organization's Surgical Safety Checklist (SSC) will lead to improved care processes and subsequently reduction of peri- and postoperative complications.

Background:

Implementation of the SSC was associated with robust reduction in morbidity and length of in-hospital stay in a stepped wedge cluster randomized controlled trial conducted in 2 Norwegian hospitals. Further investigation of precisely how the SSC improves care processes and subsequently patient outcomes is needed to understand the causal mechanisms of improvement.

Methods:

Care process metrics are reported from one of our earlier trial hospitals. Primary outcomes were in-hospital complications and care process metrics, e.g., patient warming and antibiotics. Secondary outcome was quality of SSC implementation. Analyses include Pearson's exact χ² test and binary logistic regression.

Results:

A total of 3702 procedures (1398 control vs. 2304 intervention procedures) were analyzed. High-quality SSC implementation (all 3 checklist parts) improved processes and outcomes of care. Use of forced air warming blankets increased from 35.3% to 42.4% (P < 0.001). Antibiotic administration postincision decreased from 12.5% to 9.8%, antibiotic administration preincision increased from 54.5% to 63.1%, and nonadministration of antibiotics decreased from 33.0% to 27.1%. Surgical infections decreased from 7.4% (104/1398) to 3.6% (P < 0.001). Adjusted SSC effect on surgical infections resulted in an odds ratio (OR) of 0.52 (95% confidence interval (CI): 0.38–0.72) for intervention procedures, 0.54 (95% CI: 0.37–0.79) for antibiotics provided before incision, and 0.24 (95% CI: 0.11–0.52) when using forced air warming blankets. Blood transfusion costs were reduced by 40% with the use of the SSC.

Conclusions:

When implemented well, the SSC improved operating room care processes; subsequently, high-quality SSC implementation and improved care processes led to better patient outcomes.

Intraoperative core temperature monitoring: accuracy and precision of zero-heat flux heated controlled servo sensor compared with esophageal temperature during major surgery; the ESOSPOT study

Monitoring of intraoperative core temperature is strongly recommended to reduce the risk of perioperative thermic imbalance and related complications. The zero-heat-flux sensor (3M Bair Hugger Temperature monitoring system, ZHF), measures core temperature in a non-invasive manner. This study was aimed at comparing accuracy and precision of the ZHF sensor compared to the esophageal thermometer. Patients scheduled for major elective abdominal or urologic surgery were considered eligible for enrollment. Core body temperature was measured using both an esophageal probe (T_ESO) and a ZHF sensor (T_ZHF) every 15 min from induction until the end of general anaesthesia. A Bland-Altman plot for repeated measures was performed. The proportion of measurements within ± 0.5 °C was estimated; from a clinical point of view, a proportion greater than 90% was considered sufficiently accurate. Lin's concordance correlation coefficient (CCC) for repeated measures were calculated. To evaluate association between the two methods, a generalized estimating equation (GEE) simple linear regression model, was elaborated. A GEE multiple regression model was also performed in order to adjust the estimate of the association between measurements from surgical and patient's features. Ninety-nine patients were enrolled. Bland-Altman plot bias was 0.005 °C with upper and lower limits of agreement for repeated measures of 0.50 °C and - 0.49 °C. The percentage of measurements within 0.5 °C of the reference value was 97.98% (95% confidence interval 92.89-99.75%), indicating a clinically sufficient agreement between the two methods. This was also confirmed by a CCC for repeated measures of 0.89 (95% CI 0.80 to 0.94). The GEE simple regression model (slope value of 0.77) was not significantly influenced by any patient or surgical variables. According to GEE multiple regression model results, the explored patient- and surgery-related variables did not influence the association between methods. ZHF sensor has shown a clinically acceptable accuracy and precision for body core temperature monitoring during elective major surgery. CLINICAL TRIALS: Clinical trial number: NCT03820232.

Cardiac power output accurately reflects external cardiac work over a wide range of inotropic states in pigs

BACKGROUND

Cardiac power output (CPO), derived from the product of cardiac output and mean aortic pressure, is an important yet underexploited parameter for hemodynamic monitoring of critically ill patients in the intensive-care unit (ICU). The conductance catheter-derived pressure-volume loop area reflects left ventricular stroke work (LV SW). Dividing LV SW by time, a measure of LV SW min^- 1 is obtained sharing the same unit as CPO (W). We aimed to validate CPO as a marker of LV SW min^- 1 under various inotropic states.

METHODS

We retrospectively analysed data obtained from experimental studies of the hemodynamic impact of mild hypothermia and hyperthermia on acute heart failure. Fifty-nine anaesthetized and mechanically ventilated closed-chest Landrace pigs (68 ± 1 kg) were instrumented with Swan-Ganz and LV pressure-volume catheters. Data were obtained at body temperatures of 33.0 °C, 38.0 °C and 40.5 °C; before and after: resuscitation, myocardial infarction, endotoxemia, sevoflurane-induced myocardial depression and beta-adrenergic stimulation. We plotted LVSW min^- 1 against CPO by linear regression analysis, as well as against the following classical indices of LV function and work: LV ejection fraction (LV EF), rate-pressure product (RPP), triple product (TP), LV maximum pressure (LVP_max) and maximal rate of rise of LVP (LV dP/dt_max).

RESULTS

CPO showed the best correlation with LV SW min^- 1 (r² = 0.89; p < 0.05) while LV EF did not correlate at all (r² = 0.01; p = 0.259). Further parameters correlated moderately with LV SW min^- 1 (LVP_max r² = 0.47, RPP r² = 0.67; and TP r² = 0.54). LV dP/dt_max correlated worst with LV SW min^- 1 (r² = 0.28).

CONCLUSION

CPO reflects external cardiac work over a wide range of inotropic states. These data further support the use of CPO to monitor inotropic interventions in the ICU.

New Concept Air Conditioning System for the Operating Room to Minimize Patient Cooling and Surgeon Heating: A Historical Control Cohort Study

BACKGROUND

Intraoperative hypothermia is a common adverse event. For avoiding the complication due to hypothermia, many warming devices and methods have been used in perioperative period. It has been reported that more patients undergoing laparoscopic surgery tend to have hypothermia than with open surgery. To avoid intraoperative hypothermia, many kinds of warming tools have been used. But, it was also reported that some warming methods increased perceptions of distraction and physical demand.

METHODS

To achieve both patients' normothermia and surgeons' comfort, new air conditioning (AC) system was designed with considering the characteristics of laparoscopic surgery. The temperature of the airflows to the patient and to the surgeons can be adjusted independently in this new system. The new system has two parts. One controls the temperature of the central area over the operation table. The air from this part falls on the patients. The other part is the lateral area beside the operating table; the air from this part falls on the surgeons. The subjects of this study were 160 gastric cancer patients and 316 colorectal cancer patients undergoing laparoscopic surgery. The temperature of the central flow was set 23.5 °C, and the temperature of the lateral flow was set 22 °C just after the anesthesia. The number of timepoints the patient spent in hypothermic state, defined as a temperature cooler by 0.5 °C or more than that at the starting point of surgery, was determined in each patient.

RESULTS

In the results, the rate of hypothermic state in old operation rooms was 23.8% and that in new operation rooms was 2.7% in male gastric cancer patients (p < 0.01). And those were 37.1% in old operation rooms and 0.9% in new operation rooms in female gastric cancer patients (p < 0.01). The rate of hypothermic state in old operation rooms was 30.0% and that in new operation rooms was 9.5% in male colorectal cancer patients (p < 0.01). And those were 41.6% in old operation rooms and 8.9% in new operation rooms in female colorectal cancer patients (p < 0.01). The similar results were showed in the study, which subjects were limited the patients undergoing surgery in 2015 and 2016; which were the last year the old operation rooms were used and the first year the new operation rooms were used.

CONCLUSIONS

Thus, the usefulness of the new air conditioning system for achieving both patients' normothermia and comfort of surgeons could be verified in this study.

A Comprehensive Update of Current Anesthesia Perspectives on Therapeutic Hypothermia

Normal thermal regulation is a result of the integration of afferent sensory, central control, and efferent responses to temperature change. Therapeutic hypothermia (TH) is a technique utilized during surgery to protect vital organs from ischemia; however, in doing so leads to other physiological changes. Indications for inducing hypothermia have been described for neuroprotection, coronary artery bypass graft (CABG) surgery, surgical repair of thoracoabdominal and intracranial aneurysms, pulmonary thromboendarterectomy, and arterial switch operations in neonates. Initially it was thought that induced hypothermia worked exclusively by a temperature-dependent reduction in metabolism causing a decreased demand for oxygen and glucose. Induced hypothermia exerts its neuroprotective effects through multiple underlying mechanisms including preservation of the integrity and survival of neurons through a reduction of extracellular levels of excitatory neurotransmitters dopamine and glutamate, therefore reducing central nervous system hyperexcitability. Risks of hypothermia include increased infection risk, altered drug pharmacokinetics, and systemic cardiovascular changes. Indications for TH include ischemia-inducing surgeries and diseases. Two commonly used methods are used to induce TH, surface cooling and endovascular cooling. Core body temperature monitoring is essential during induction of TH and rewarming, with central venous temperature as the gold standard. The aim of this review is to highlight current literature discussing perioperative considerations of TH including risks, benefits, indications, methods, and monitoring.

Heating and Cooling Rates With an Esophageal Heat Exchange System

BACKGROUND

The Esophageal Cooling Device circulates warm or cool water through an esophageal heat exchanger, but warming and cooling efficacy in patients remains unknown. We therefore determined heat exchange rates during warming and cooling.

METHODS

Nineteen patients completed the trial. All had general endotracheal anesthesia for nonthoracic surgery. Intraoperative heat transfer was measured during cooling (exchanger fluid at 7°C) and warming (fluid at 42°C). Each was evaluated for 30 minutes, with the initial condition determined randomly, starting at least 40 minutes after induction of anesthesia. Heat transfer rate was estimated from fluid flow through the esophageal heat exchanger and inflow and outflow temperatures. Core temperature was estimated from a zero-heat-flux thermometer positioned on the forehead.

RESULTS

Mean heat transfer rate during warming was 18 (95% confidence interval, 16-20) W, which increased core temperature at a rate of 0.5°C/h ± 0.6°C/h (mean ± standard deviation). During cooling, mean heat transfer rate was -53 (-59 to -48) W, which decreased core temperature at a rate of 0.9°C/h ± 0.9°C/h.

CONCLUSIONS

Esophageal warming transferred 18 W which is considerably less than the 80 W reported with lower or upper body forced-air covers. However, esophageal warming can be used to supplement surface warming or provide warming in cases not amenable to surface warming. Esophageal cooling transferred more than twice as much heat as warming, consequent to the much larger difference between core and circulating fluid temperature with cooling (29°C) than warming (6°C). Esophageal cooling extracts less heat than endovascular catheters but can be used to supplement catheter-based cooling or possibly replace them in appropriate patients.

Developing a personalized closed-loop controller of medically-induced coma in a rodent model

OBJECTIVE

Personalized automatic control of medically-induced coma, a critical multi-day therapy in the intensive care unit, could greatly benefit clinical care and further provide a novel scientific tool for investigating how the brain response to anesthetic infusion rate changes during therapy. Personalized control would require real-time tracking of inter- and intra-subject variabilities in the brain response to anesthetic infusion rate while simultaneously delivering the therapy, which has not been achieved. Current control systems for medically-induced coma require a separate offline model fitting experiment to deal with inter-subject variabilities, which would lead to therapy interruption. Removing the need for these offline interruptions could help facilitate clinical feasbility. In addition, current systems do not track intra-subject variabilities. Tracking intra-subject variabilities is essential for studying whether or how the brain response to anesthetic infusion rate changes during therapy. Further, such tracking could enhance control precison and thus help facilitate clinical feasibility.

APPROACH

Here we develop a personalized closed-loop anesthetic delivery (CLAD) system in a rodent model that tracks both inter- and intra-subject variabilities in real time while simultaneously controlling the anesthetic in closed loop. We tested the CLAD in rats by administrating propofol to control the electroencephalogram (EEG) burst suppression. We first examined whether the CLAD can remove the need for offline model fitting interruption. We then used the CLAD as a tool to study whether and how the brain response to anesthetic infusion rate changes as a function of changes in the depth of medically-induced coma. Finally, we studied whether the CLAD can enhance control compared with prior systems by tracking intra-subject variabilities.

MAIN RESULTS

The CLAD precisely controlled the EEG burst suppression in each rat without performing offline model fitting experiments. Further, using the CLAD, we discovered that the brain response to anesthetic infusion rate varied during control, and that these variations correlated with the depth of medically-induced coma in a consistent manner across individual rats. Finally, tracking these variations reduced control bias and error by more than 70% compared with prior systems.

SIGNIFICANCE

This personalized CLAD provides a new tool to study the dynamics of brain response to anesthetic infusion rate and has significant implications for enabling clinically-feasible automatic control of medically-induced coma.

Monophasic transcranial constant-current versus constant-voltage stimulation of motor-evoked potentials during spinal surgery

Constant-voltage and constant-current stimulators may be used for transcranial electrical stimulation of motor evoked potentials (TES-MEP). However, no previous report has determined whether the two monophasic stimulation methods lead to similar responses during intra-operative monitoring. We studied differences in the lateralities of compound muscle action potentials (CMAPs) during intra-operative spinal cord monitoring via TES-MEP using monophasic constant-current and constant-voltage stimulations. CMAPs were bilaterally recorded from the upper and lower limb muscles in 95 patients who underwent elective spine and spinal cord surgery. We used two monophasic stimulation patterns: pattern 1, right anode and left cathode; pattern 2, right cathode and left anode. There were no statistically significant differences between the right and left sides with respect to success rates, wave amplitudes, and efficiencies, with constant-voltage stimulation, however, there were statistically significant differences between the right and left sides with constant-current stimulation. In case of our stimulation condition, there were no statistically significant differences between the right and left sides with respect to CMAPs with constant-voltage stimulation; constant-current stimulation was influenced by the type of monophasic stimulation, which necessitates the switch the polarity of the stimulation to bilaterally record CMAPs.

The focus of temperature monitoring with zero-heat-flux technology (3M Bair-Hugger): a clinical study with patients undergoing craniotomy

In the noninvasive zero-heat-flux (ZHF) method, deep body temperature is brought to the skin surface when an insulated temperature probe with servo-controlled heating on the skin creates a region of ZHF from the core to the skin. The sensor of the commercial Bair-Hugger ZHF device is placed on the forehead. According to the manufacturer, the sensor reaches a depth of 1-2 cm below the skin. In this observational study, the anatomical focus of the Bair-Hugger ZHF sensor was assessed in pre- and postoperative CT or MRI images of 29 patients undergoing elective craniotomy. Assuming the 2-cm depth from the forehead skin surface, the temperature measurement point preoperatively reached the brain cortex in all except one patient. Assuming the 1-cm depth, the preoperative temperature measurement point did not reach the brain parenchyma in any of the patients and was at the cortical surface in two patients. Corresponding results were obtained postoperatively, although either sub-arachnoid fluid or air was observed in all CT/MRI images. Craniotomy did not have a detectable effect on the course of the ZHF temperatures. In Bland-Altman analysis, the agreement of ZHF temperature with the nasopharyngeal temperature was 0.11 (95% confidence interval - 0.54 to 0.75) °C and with the bladder temperature - 0.14 (- 0.81 to 0.52) °C. As conclusions, within the reported range of the Bair-Hugger ZHF measurement depth, the anatomical focus of the sensor cannot be determined. Craniotomy did not have a detectable effect on the course of the ZHF temperatures that showed good agreement with the nasopharyngeal and bladder temperatures.

An evaluation of anesthetic fade in motor evoked potential monitoring in spinal deformity surgeries

Background

Intraoperative neuromonitoring using motor evoked potentials (MEP) satisfactorily detects motor tract integrity changes during spinal surgery. However, monitoring is affected by “anesthetic fade,” in which the stimulation threshold increases because the waveform amplitude decreases with the accumulation of propofol. Therefore, the purpose of this study was to clarify the effect of anesthetic fade on transcranial MEPs by investigating the time-dependent changes of amplitude during spinal deformity surgeries.

Methods

We retrospectively reviewed medical records of 142 spinal deformity patients (66 patients with idiopathic scoliosis, 28 with adult spinal deformities, 19 with neuromuscular scoliosis, 17 with syndromic scoliosis, and 12 with congenital scoliosis). The average age was 28 years (range, 5 to 81 years). MEPs were recorded bilaterally from the abductor digiti minimi (ADM) and abductor hallucis (AH) muscles during spinal deformity surgeries. The Wilcoxon signed-rank test was used to investigate the time-dependent changes of amplitude after propofol infusion to evaluate anesthetic fade effects.

Results

The average time to baseline from initial propofol infusion was 113 min (range, 45 to 182 min). In the ADM, the amplitude was 52% at 1 h after initial propofol infusion, 102% at 2 h, 105% at 3 h, 101% at 4 h, 86% at 5 h, and 81% at 6 h. Compared to the 2-h time point, MEP decreased significantly by 16% at 5 h (P < 0.0005) and by 21% at 6 h (P < 0.05). In the AH, the amplitude was 49% at 1 h after initial infusion of propofol, 102% at 2 h, 102% at 3 h, 92% at 4 h, 71% at 5 h, and 63% at 6 h. Compared to the 2-h time point, MEP decreased significantly by 10% at 4 h (P < 0.005), by 31% at 5 h (P < 0.0000005), and by 39% at 6 h (P < 0.05).

Conclusions

MEP amplitude significantly decreased in the upper limbs at 5 and 6 h and in the lower limbs at 4, 5, and 6 h after the initial infusion of propofol, respectively. The influence of anesthetic fade could influence false positive MEPs during long spinal surgeries.

Examination of intra-operative core temperature in joint arthroplasty: a single-institution prospective observational study

PURPOSE

Peri-operative hypothermia is associated with increased blood loss, delayed wound healing, and surgical site infections. However, it is not known when or how rapidly hypothermia develops during arthroplasty. This study observed patients undergoing lower extremity arthroplasty to identify the times of greatest heat loss or gain.

METHODS

This single-institution prospective observational study enrolled 120 patients undergoing elective knee or hip arthroplasty for peri-operative temporal temperature measurements at ten prespecified intervals. Incidence of hypothermia was the primary outcome. A secondary aim was to identify patient and operative factors associated with hypothermia. Descriptive statistics were calculated for fixed time variables. Associations for the occurrence of hypothermia over time were conducted using generalized linear mixed models with a logit link and a random subject effect to account for repeated measures on the same individual over time.

RESULTS

Most patients, 72.6%, experienced hypothermia with 20.6% hypothermic for over one hour and 47.1% hypothermic after surgery. In the multivariable model, increased odds of hypothermia were associated with female gender (P = 0.017), knee arthroplasty (P < 0.001), neuraxial anaesthesia (P < 0.001), lower patient pre-operative temperature (P < 0.001), and lower operating room temperature (P = 0.042). A 0.5 °C decrease in patient pre-operative temperature or operating room temperature was associated with a 97 and 11% increase in the odds of hypothermia, respectively, controlling for other factors.

CONCLUSION

In our series, peri-operative hypothermia remains common for patients undergoing arthroplasty. Female gender, low pre-operative temperature, knee arthroplasty, and neuraxial anesthesia were associated with hypothermia. Further preventative strategies and studies on interventions to reduce hypothermia are needed.

Prolonged paralysis with atracurium use in a patient with Rubinstein-Taybi syndrome

Rubinstein-Taybi syndrome (RTS) is a rare autosomal dominant disorder that occurs due to a microdeletion of chromosome 16p13. The craniofacial abnormalities in these patients may pose a challenge for anaesthetist performing tracheal intubation. However, there are no known reported cases of drug interaction with non-depolarising muscle relaxant in patients with RTS. This young patient with RTS presented with an unexpected prolonged atracurium effect during the course of anaesthesia. After ruling out other possible causes, we have come to a conclusion that RTS itself could have played a role in the prolonged effect of atracurium. However, further studies will be needed to confirm this hypothesis. In the meantime, care should be used when using muscle relaxants in patients with RTS.

Establishment and Validation of a Prediction Equation to Estimate Risk of Intraoperative Hypothermia in Patients Receiving General Anesthesia

Inadvertent intraoperative hypothermia (core temperature <36 °C) is a frequent but preventable complication of general anesthesia. Accurate risk assessment of individual patients may help physicians identify patients at risk for hypothermia and apply preventive approaches, which include active intraoperative warming. This study aimed to develop and validate a risk-prediction model for intraoperative hypothermia. Two independent observational studies in China, the Beijing Regional Survey and the China National Survey, were conducted in 2013 and 2014, respectively, to determine the incidence of hypothermia and its underlying risk factors. In this study, using data from these two studies, we first derived a risk calculation equation, estimating the predictive risk of hypothermia using National Survey data (3132 patients), then validated the equation using the Beijing Regional Survey data (830 patients). Measures of accuracy, discrimination and calibration were calculated in the validation data set. Through validation, this model, named Predictors Score, had sound overall accuracy (Brier Score = 0.211), good discrimination (C-Statistic = 0.759) and excellent calibration (Hosmer-Lemeshow, P = 0.5611). We conclude that the Predictors Score is a valid predictor of the risk of operative hypothermia and can be used in deciding whether intraoperative warming is a cost-effective measure in preventing the hypothermia.

A Population Pharmacokinetic Analysis to Study the Effect of Therapeutic Hypothermia on Vancomycin Disposition in Children Resuscitated From Cardiac Arrest

OBJECTIVES

Limited data exist on the effects of therapeutic hypothermia on renal function and pharmacokinetics in pediatric patients after cardiac arrest. The objective was to describe the differences in vancomycin disposition in pediatric patients following cardiac arrest treated with either therapeutic hypothermia or normothermia using population pharmacokinetic modeling.

DESIGN

Single-center, retrospective cohort study.

SETTING

A tertiary care hospital pediatric and cardiac ICU.

PATIENTS

Fifty-two pediatric patients (30 d to 17 yr old) who experienced a cardiac arrest, received vancomycin, and were treated with therapeutic hypothermia (32-34°C) or normothermia (36.3-37.6°C) between January 1, 2010, and September 30, 2014, were reviewed.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

A two-compartment model with linear elimination, weight effects on clearance, intercompartmental clearance (Q), central volume of distribution (V1), and peripheral volume of distribution (V2) adequately described the data despite high variability due to the small sample size. The typical value of clearance in this study was 4.48 L/hr (0.19 L/hr/kg) for a normothermic patient weighing 70 kg and a glomerular filtration rate of 90 mL/min/1.73 m. Patients treated with normothermia but with reduced or poor renal function (≤ 90 mL/min/1.73 m) had up to an 80% reduction in vancomycin clearance compared to those with normal renal function (90-140 mL/min/1.73 m). Patients with normal renal function but treated with therapeutic hypothermia versus normothermia experienced up to 25% reduction in vancomycin clearance. Patients treated with therapeutic hypothermia and with poor renal function experienced up to an 84% reduction in vancomycin clearance.

CONCLUSIONS

Patients receiving hypothermia and/or with decreased renal function had lower vancomycin clearances based on a retrospectively fitted two-compartment model in children who experience cardiac arrest.

Intraoperative hypothermia and its clinical outcomes in patients undergoing general anesthesia: National study in China

BACKGROUND/OBJECTIVE

Inadvertent intraoperative hypothermia (core temperature <36°C) is a frequently preventable complication with several adverse consequences. Our study aimed to determine the overall incidence of inadvertent intraoperative hypothermia and its risk factors associated with clinical outcomes in this national survey in China.

METHODS

We conducted a national cross-sectional study with 30 days postoperative follow-up from November 2014 through August 2015. A total of 3132 eligible patients underwent general anesthesia were randomly selected from 28 hospitals in the nationwide of China.

RESULTS

The overall incidence of intraoperative hypothermia was as high as 44.3%, in which cumulative incidence rates of hypothermia being 17.8%, 36.2%, 42.5% and 44.1% within 1 h, 2 h, 3 h and 4 h respectively following induction of anesthesia. All patients were warmed passively by covering of surgical draping, sheets or cotton blankets, whereas only 14.2% of patients received active warming with space heaters or electric heater or electronic blankets. Compared to normothermic patients, patients with hypothermia is associated with more postoperative ICU admit, longer PACU and more postoperative hospital days, but no difference in surgical site infection (SSI) rates or 30-day mortality. Several factors were shown to be associated with decreased risk of hypothermia. They are active warming (OR = 0.46, 95% CI 0.26-0.81), BMI ≥ 25 (OR = 0.54, 95% CI 0.45-0.65), higher baseline core temperature (OR = 0.04, 95% CI 0.03-0.06), and higher ambient temperature (OR = 0.83, 95% CI 0.78-0.88). Risk factors associated with an increased risk of hypothermia included major-plus surgery (OR = 1.49, 95% CI 1.23-1.79), and long anesthesia (>2 h) (OR = 2.60, 95% CI 2.09-3.24).

CONCLUSIONS

The incidence of intraoperative hypothermia in China is high, and the rate of active warming of patients during operation is low. Hypothermia is associated with more postoperative shivering, increased ICU admissions, and longer postoperative hospital days.

Comparison of Butorphanol and Fentanyl for the Relief of Postoperative Shivering Associated with Spinal Anesthesia

AIM

The aim of this study was to compare fentanyl and butorphanol for the relief of postoperative shivering in spinal anesthesia.

MATERIALS AND METHODS

A total of 100 American Society of Anesthesiologists physical status Class I and II patients aged 19-60 years belonging to both sexes who were posted for elective surgical procedures under spinal anesthesia were divided into two groups (fentanyl and butorphanol) and monitored intraoperatively for the occurrence of shivering and time taken to control shivering after administration of fentanyl and butorphanol drugs.

RESULTS

Relief of shivering is rapid and more effective with fentanyl than butorphanol. There is a significant increase in pulse rate, mean arterial pressure, respiratory rate (RR), and decreased in oxygen saturation at the onset of shivering and also a decrease in core body temperature. Sedation, nausea, vomiting, and recurrence of shivering are more with butorphanol with fentanyl.

CONCLUSION

On the basis of the study, it is concluded that fentanyl is more effective and takes less time to control perioperative shivering as compared to butorphanol.

Intravenous nutrients for preventing inadvertent perioperative hypothermia in adults

BACKGROUND

Inadvertent perioperative hypothermia (a drop in core temperature to below 36°C) occurs because normal temperature regulation is disrupted during surgery, mainly because of the effects of anaesthetic drugs and exposure of the skin for prolonged periods. Many different ways of maintaining body temperature have been proposed, one of which involves administration of intravenous nutrients during the perioperative period that may reduce heat loss by increasing metabolism, thereby increasing heat production.

OBJECTIVES

To assess the effectiveness of preoperative or intraoperative intravenous nutrients in preventing perioperative hypothermia and its complications during surgery in adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL; November 2015) in the Cochrane Library; MEDLINE, Ovid SP (1956 to November 2015); Embase, Ovid SP (1982 to November 2015); the Institute for Scientific Information (ISI) Web of Science (1950 to November 2015); and the Cumulative Index to Nursing and Allied Health Literature (CINAHL, EBSCO host; 1980 to November 2015), as well as the reference lists of identified articles. We also searched the Current Controlled Trials website and ClincalTrials.gov.

SELECTION CRITERIA

Randomized controlled trials (RCTs) of intravenous nutrients compared with control or other interventions given to maintain normothermia in adults undergoing surgery.

DATA COLLECTION AND ANALYSIS

Two review authors extracted data and assessed risk of bias for each included trial, and a third review author checked details if necessary. We contacted some study authors to request additional information.

MAIN RESULTS

We included 14 trials (n = 565), 13 (n = 525) of which compared intravenous administration of amino acids to a control (usually saline solution or Ringer's lactate). The remaining trial (n = 40) compared intravenous administration of fructose versus a control. We noted much variation in these trials, which used different types of surgery, variable durations of surgery, and different types of participants. Most trials were at high or unclear risk of bias owing to inappropriate or unclear randomization methods, and to unclear participant and assessor blinding. This may have influenced results, but it is unclear how results might have been influenced.No trials reported any of our prespecified primary outcomes, which were risk of hypothermia and major cardiovascular events. Therefore, we decided to analyse data related to core body temperature instead as a primary outcome. It was not possible to conduct meta-analysis of data related to amino acid infusion for the 60-minute and 120-minute time points, as we observed significant statistical heterogeneity in the results. Some trials showed that higher temperatures were associated with amino acids, but not all trials reported statistically significant results, and some trials reported the opposite result, where the amino acid group had a lower core temperature than the control group. It was possible to conduct meta-analysis for six studies (n = 249) that provided data relating to the end of surgery. Amino acids led to a statistically significant increase in core temperature in comparison to those receiving control (MD = 0.46°C 95% CI 0.33 to 0.59; I2 0.0%; random-effects; moderate quality evidence).Three trials (n = 155) reported shivering as an outcome. Meta-analysis did not show a clear effect, and so it is uncertain whether amino acids reduce the risk of shivering (RR 0.36, 95% CI 0.13 to 1.00; I2 = 93%; random-effects model; very low-quality evidence).

AUTHORS' CONCLUSIONS

Intravenous amino acids may keep participants up to a half-degree C warmer than the control. This difference was statistically significant at the end of surgery, but not at other time points. However, the clinical importance of this finding remains unclear. It is also unclear whether amino acids have any effect on the risk of shivering and if intravenous nutrients confer any other benefits or harms, as high-quality data about these outcomes are lacking.

Preoperative interscalene brachial plexus block aids in perioperative temperature management during arthroscopic shoulder surgery

Background

Hypothermia is common during arthroscopic shoulder surgery under general anesthesia, and anesthetic-impaired thermoregulation is thought to be the major cause of hypothermia. This prospective, randomized, double-blind study was designed to compare perioperative temperature during arthroscopic shoulder surgery with interscalene brachial plexus block (IBPB) followed by general anesthesia vs. general anesthesia alone.

Methods

Patients scheduled for arthroscopic shoulder surgery were randomly allocated to receive IBPB followed by general anesthesia (group GB, n = 20) or general anesthesia alone (group GO, n = 20), and intraoperative and postoperative body temperatures were measured.

Results

The initial body temperatures were 36.5 ± 0.3℃ vs. 36.4 ± 0.4℃ in group GB vs. GO, respectively (P = 0.215). The body temperature at 120 minutes after induction of anesthesia was significantly higher in group GB than in group GO (35.8 ± 0.3℃ vs. 34.9 ± 0.3℃; P < 0.001). The body temperatures at 60 minutes after admission to the post-anesthesia care unit were 35.8 ± 0.3℃ vs. 35.2 ± 0.2℃ in group GB vs. GO, respectively (P < 0.001). The concentrations of desflurane at 0, 15, and 120 minutes after induction of anesthesia were 6.0 vs. 6.0% (P = 0.330), 5.0 ± 0.8% vs. 5.8 ± 0.4% (P = 0.001), and 3.4 ± 0.4% vs. 7.1 ± 0.9% (P < 0.001) in group GB vs. GO, respectively.

Conclusions

The present study demonstrated that preoperative IBPB could reduce both the intraoperative concentration of desflurane and the reduction in body temperature during and after arthroscopic shoulder surgery.

Early Absent Pupillary Light Reflexes After Cardiac Arrest in Patients Treated with Therapeutic Hypothermia

Loss of pupillary light reactivity is one recognized indicator of poor prognosis after cardiopulmonary resuscitation (CPR). However, drug overdose, low cardiac output, and/or resuscitation drugs can lead to impaired pupillary light reflex. To investigate pupillary light reflex status before therapeutic hypothermia (TH) in relation to neurological outcome, we retrospectively reviewed the data of a prospectively implemented TH protocol in patients with cardiac arrest (CA) at Mayo Clinic in Jacksonville, Florida (January 2006-January 2012), and Mayo Clinic in Scottsdale, Arizona (August 2010-March 2014). During this period, all CA patients who underwent hypothermia were included. These patients were selected from an institutional database and hypothermia data set. The Cerebral Performance Category (CPC) at time of discharge was our primary outcome measure. A CPC of 1 to 2 was defined as good outcome and a CPC from 3 to 5 was defined as poor outcome. We identified 99 patients who had CA treated with TH. Twenty-nine patients (29%) had pupils that were nonreactive to light on admission examination before TH, eight of whom later had return of pupil reactivity by day 3. Two of these 29 patients (6.9%) had good outcome, compared to 24 of 70 patients (34.3%) with pupils that were reactive to light (p = 0.005). Both of these patients had CA after illicit drug overdose. Early nonreactive pupils occurred in almost a third of patients after CPR and before TH in our patient population. Recovery of pupillary light reactivity is possible, and in a small minority of those cases (particularly when CA is preceded by the use of illicit drugs), a good outcome can be achieved.

Moderate-dose sedation and analgesia during targeted temperature management after cardiac arrest

BACKGROUND

Sedation and analgesia regimens during targeted temperature management (TTM), after cardiac arrest varies widely, are poorly described in the literature and may have a negative impact on outcome. Since implementing TTM in 2005, we have used moderate-dose sedation and describe our experience with this approach.

METHODS

In this retrospective review, we included patients treated with TTM for cardiac arrest at our institution for 2008-2012. Patients received TTM if they did not follow verbal commands following cardiac arrest, regardless of place of arrest or rhythm. Utstein-compatible data were prospectively entered into the International Cardiac Arrest Registry, supplemented by review of nursing, pharmacy, and physical therapy records. We report analgesic and sedative medications and doses during the 24 h of active TTM at 33 °C, resource utilization, and important clinical events.

RESULTS

166 patients treated with TTM after in- and out-of-hospital cardiac arrest with complete data were included. Overall survival was 42 %, median time to following commands was 3 h after rewarming (-6, 14), time to spontaneous breathing trial was 19 h (5-35), time to extubation was 28 h (9-60), and 59 % of survivors were discharged directly home at 13 (10-20) days. The incidence of seizure was 6 %, septic shock 4 %, and pneumonia 32 %. Four survivors required tracheostomy at 8, 8, 12, and 16 days.

CONCLUSIONS

A moderate-dose sedation and analgesia regimen was well tolerated and effective during therapeutic hypothermia after cardiac arrest and is an effective alternative to very deep sedation. We recommend more complete description of sedation and analgesia protocols in future studies, including expanded outcome reporting to include variables affected by sedation therapy. Further study is required to define which sedation approach for TTM may be best.

Perioperative hypothermia: Causes, consequences and treatment

Perioperative hypothermia, core temperature below 36.0 °C, transpires due to disruption of thermoregulation by anesthesia coupled with cold exposure to procedural surroundings and cleansing agents. Although most publications have focused on thermoregulation disruption with general anesthesia, neuraxial anesthesia may also cause significant hypothermia. The clinical consequences of perioperative hypothermia are multiple and include patient discomfort, shivering, platelet dysfunction, coagulopathy, and increased vasoconstriction associated with a higher risk of wound infection. Furthermore, postoperative cardiac events occur at a higher rate; although it is unclear whether this is due to increased oxygen consumption or norepinephrine levels. Hypothermia may also affect pharmacokinetics and prolong postoperative recovery times and hospital length of stay. In order to combat perioperative hypothermia, many prevention strategies have been examined. Active and passive cutaneous warming are likely the most common and aim to both warm and prevent heat loss; many consider active warming a standard of care for surgeries over one hour. Intravenous nutrients have also been examined to boost metabolic heat production. Additionally, pharmacologic agents that induce vasoconstriction have been studied with the goal of minimizing heat loss. Despite these multiple strategies for prevention and treatment, hypothermia continues to be a problem and a common consequence of the perioperative period. This literature review presents the most recent evidence on the disruption of temperature regulation by anesthesia and perioperative environment, the consequences of hypothermia, and the methods for hypothermia prevention and treatment.

Effect of acute hypervolemic hemodilution of 6% hydroxyethyl starch 130/0.4 on the EC50 of propofol at two clinical endpoints in patients

Preoperative acute hypervolemic hemodilution (AHHD) is a technique used in anesthesia to reduce the number of blood cells lost during intraoperative bleeding. The aim of the present study was to evaluate the effect of the hypervolemic hemodilution of 6% hydroxyethyl starch 130/0.4 on the EC₅₀ of propofol at two clinical endpoints. A total of 20 patients undergoing AHHD following epidural anesthesia were studied, and 20 patients who did not receive hemodilution were used as a control group. All patients were American Society of Anesthesiologists grade I, aged 20-40 years and undergoing hip arthroplasty surgery. In the AHHD group, 10 ml/kg lactated Ringer's solution was infused over 20 min at the same time as the epidural test dose. The infusion was followed by the infusion of 6% hydroxyethyl starch 130/0.4 over 30 min. Patients in the control group received 10 ml/kg Ringer's solution over 50 min. Propofol was then delivered by a Diprifusor target-controlled infusion. The predicted blood and effect-site propofol concentrations were recorded at loss of consciousness (LOC) and return of consciousness (ROC). Probit analysis was used to estimate the values for predicted blood and effect-site concentrations at the two clinical endpoints. The results showed that the potency of propofol was decreased during AHHD. Compared with the controls, the predicted blood and effect-site concentrations of propofol at LOC were higher in patients of the hemodilution group, resulting in higher EC₅₀ values (P=0.001 and 0.025, respectively). At ROC, the effect-site EC₅₀ was 2.9 µg/ml [95% confidence interval (CI), 2.8-3.0] in hemodilution patients and 2.5 µg/ml (95% CI, 2.2-2.6) in control patients (P=0.001). With AHHD, the LOC time was significantly longer and the propofol dose was higher, while ROC times were comparable. In conclusion, AHHD increases the requirement for propofol at LOC and prolongs LOC time. Patients with AHHD recovered consciousness at higher effect-site concentrations of propofol. Thus, the induction dose of propofol should be increased during AHHD.

Neurological prognostication after cardiac arrest

PURPOSE OF REVIEW

Prediction of neurological prognosis in patients who are comatose after successful resuscitation from cardiac arrest remains difficult. Previous guidelines recommended ocular reflexes, somatosensory evoked potentials and serum biomarkers for predicting poor outcome within 72  h from cardiac arrest. However, these guidelines were based on patients not treated with targeted temperature management and did not appropriately address important biases in literature.

RECENT FINDINGS

Recent evidence reviews detected important limitations in prognostication studies, such as low precision and, most importantly, lack of blinding, which may have caused a self-fulfilling prophecy and overestimated the specificity of index tests. Maintenance of targeted temperature using sedatives and muscle relaxants may interfere with clinical examination, making assessment of neurological status before 72  h or more after cardiac arrest unreliable.

SUMMARY

No index predicts poor neurological outcome after cardiac arrest with absolute certainty. Prognostic evaluation should start not earlier than 72  h after ROSC and only after major confounders have been excluded so that reliable clinical examination can be made. Multimodality appears to be the most reasonable approach for prognostication after cardiac arrest.

Warming of intravenous and irrigation fluids for preventing inadvertent perioperative hypothermia

BACKGROUND

Inadvertent perioperative hypothermia (a drop in core temperature to below 36°C) occurs because of interference with normal temperature regulation by anaesthetic drugs, exposure of skin for prolonged periods and receipt of large volumes of intravenous and irrigation fluids. If the temperature of these fluids is below core body temperature, they can cause significant heat loss. Warming intravenous and irrigation fluids to core body temperature or above might prevent some of this heat loss and subsequent hypothermia.

OBJECTIVES

To estimate the effectiveness of preoperative or intraoperative warming, or both, of intravenous and irrigation fluids in preventing perioperative hypothermia and its complications during surgery in adults.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials (CENTRAL) (2014, Issue 2), MEDLINE Ovid SP (1956 to 4 February 2014), EMBASE Ovid SP (1982 to 4 February 2014), the Institute for Scientific Information (ISI) Web of Science (1950 to 4 February 2014), Cumulative Index to Nursing and Allied Health Literature (CINAHL) EBSCOhost (1980 to 4 February 2014) and reference lists of identified articles. We also searched the Current Controlled Trials website and ClinicalTrials.gov.

SELECTION CRITERIA

We included randomized controlled trials or quasi-randomized controlled trials comparing fluid warming methods versus standard care or versus other warming methods used to maintain normothermia.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data from eligible trials and settled disputes with a third review author. We contacted study authors to ask for additional details when needed. We collected data on adverse events only if they were reported in the trials.

MAIN RESULTS

We included in this review 24 studies with a total of 1250 participants. The trials included various numbers and types of participants. Investigators used a range of methods to warm fluids to temperatures between 37°C and 41°C. We found that evidence was of moderate quality because descriptions of trial design were often unclear, resulting in high or unclear risk of bias due to inappropriate or unclear randomization and blinding procedures. These factors may have influenced results in some way. Our protocol specified the risk of hypothermia as the primary outcome; as no trials reported this, we decided to include data related to mean core temperature. The only secondary outcome reported in the trials that provided useable data was shivering. Evidence was unclear regarding the effects of fluid warming on bleeding. No data were reported on our other specified outcomes of cardiovascular complications, infection, pressure ulcers, bleeding, mortality, length of stay, unplanned intensive care admission and adverse events.Researchers found that warmed intravenous fluids kept the core temperature of study participants about half a degree warmer than that of participants given room temperature intravenous fluids at 30, 60, 90 and 120 minutes, and at the end of surgery. Warmed intravenous fluids also further reduced the risk of shivering compared with room temperature intravenous fluidsInvestigators reported no statistically significant differences in core body temperature or shivering between individuals given warmed and room temperature irrigation fluids.

AUTHORS' CONCLUSIONS

Warm intravenous fluids appear to keep patients warmer during surgery than room temperature fluids. It is unclear whether the actual differences in temperature are clinically meaningful, or if other benefits or harms are associated with the use of warmed fluids. It is also unclear if using fluid warming in addition to other warming methods confers any benefit, as a ceiling effect is likely when multiple methods of warming are used.