The relationship between perioperative temperature and adverse outcomes after off-pump coronary artery bypass graft surgery

2024 AHA/ACC/ACS/ASNC/HRS/SCA/SCCT/SCMR/SVM Guideline for Perioperative Cardiovascular Management for Noncardiac Surgery: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines

AIM

The "2024 AHA/ACC/ACS/ASNC/HRS/SCA/SCCT/SCMR/SVM Guideline for Perioperative Cardiovascular Management for Noncardiac Surgery" provides recommendations to guide clinicians in the perioperative cardiovascular evaluation and management of adult patients undergoing noncardiac surgery.

METHODS

A comprehensive literature search was conducted from August 2022 to March 2023 to identify clinical studies, reviews, and other evidence conducted on human subjects that were published in English from MEDLINE (through PubMed), EMBASE, the Cochrane Library, the Agency for Healthcare Research and Quality, and other selected databases relevant to this guideline.

STRUCTURE

Recommendations from the "2014 ACC/AHA Guideline on Perioperative Cardiovascular Evaluation and Management of Patients Undergoing Noncardiac Surgery" have been updated with new evidence consolidated to guide clinicians; clinicians should be advised this guideline supersedes the previously published 2014 guideline. In addition, evidence-based management strategies, including pharmacological therapies, perioperative monitoring, and devices, for cardiovascular disease and associated medical conditions, have been developed.

Association Between Body Temperature and In-Hospital Mortality Among Congestive Heart Failure Patients with Diabetes in Intensive Care Unit: A Retrospective Cohort Study

Body temperature (BT) has been utilized to assess patient outcomes across various diseases. However, the impact of BT on mortality in the intensive care unit (ICU) among patients with congestive heart failure (CHF) and diabetes mellitus (DM) remains unclear. We conducted a retrospective cohort study using data from the Medical Information Mart for Intensive Care (MIMIC)-IV data set. The primary outcome assessed was in-hospital mortality rates. BT was treated as a categorical variable in the analyses. The association between BT on ICU admission and in-hospital mortality was examined using multivariable logistic regression models, restricted cubic spline, and subgroup analysis. The cohort comprised 7063 patients with both DM and CHF (3135 females and 3928 males), with an average age of 71.5 ± 12.2 years. Comparative analysis of the reference group (Q4) revealed increased in-hospital mortality in Q6 and Q1 temperature groups, with fully adjusted odds ratios of 2.08 (95% confidence interval [CI]: 1.45-2.96) and 1.95 (95% CI: 1.35-2.79), respectively. Restricted cubic spline analysis demonstrated a U-shaped relationship between temperature on admission and mortality risk (p nonlinearity <0.001), with the nadir of risk observed at 36.8°C. The effect sizes and corresponding CIs below and above the threshold were 0.581 (95% CI: 0.434-0.777) and 1.674 (95% CI: 1.204-2.328), respectively. Stratified analyses further validated the robustness of this correlation. Our study establishes a nonlinear association between BT and in-hospital mortality in patients with both CHF and DM, with optimal suitable BT at 36.8°C. Further research is necessary to confirm this relationship.

Reliability of different body temperature measurement sites during normothermic cardiac surgery

INTRODUCTION

Patients undergoing cardiac surgery can experience significant thermal changes during the perioperative period and, for that reason, it is essential to monitor temperatures with adequate accuracy and precision during cardiopulmonary bypass (CPB). The primary aim of the current study was to measure the discrepancies between temperatures at different body sites during normothermic or mild hypothermic CPB.

METHODS

48 patients undergoing cardiac surgery participated in our study. Simultaneous temperatures were measured at nasopharynx, pulmonary artery, arterial outlet, venous inlet, forehead using a heat flux sensor, and urinary bladder at 5-min intervals throughout surgery. The Bland-Altman plot for repeated measures was used to assess concordance between methods.

RESULTS

The duration of surgery was 360 min (interquartile range (IQR) 300-412), while the median cross-clamp time was 135 min (IQR 101-169). During the CPB time, the average difference between arterial outlet and nasopharyngeal temperature was -0.16°C (95% limits of agreement of ±0.93). The bias between arterial outlet and the venous inflow was 0.16°C and the 95% limits of agreement were -0.63 to 0.95°C. The Bland-Altman analysis showed an average difference between oxigenator arterial outlet and bladder probe of -0.62 (95% limits of agreement of ±1.3). The average difference between arterial outlet and Tcore™ temperatures was 0.08°C (95% limits of agreement of ±1.46). 25 patients (52.08%) presented nasopharyngeal temperatures higher than 37°C in the post-CPB period, but none of them exceeded 38°C.

CONCLUSIONS

Perfusionists should be cautious when using the nasopharyngeal site as the only surrogate of brain temperature, even in normothermic cardiac surgery because the precision of measurements is not entirely adequate.

Association between first 24-h mean body temperature and mortality in patients with diastolic heart failure in intensive care unit: A retrospective cohort study

Background

Body temperature (BT) has been used to evaluate the outcomes of patients with various diseases. In this study, patients with diastolic heart failure (DHF) in the intensive care unit (ICU) were examined for a correlation between BT and mortality.

Methods

This was a retrospective cohort study of the Medical Information Mart for Intensive Care (MIMIC)-IV dataset. A total of 4,153 patients with DHF were included. The primary outcomes were 28-day ICU and higher in-hospital mortality rates. BT was used in the analyses both as a continuous variable and as a categorical variable. According to the distribution of BT, the patients were categorized into three groups (hypothermia BT <36.5°C, normal 36.5°C ≤ BT <37.5°C, and hyperthermia BT ≥37.5°C). Multivariate logistic regression analysis was performed to explore the association between BT and patient outcomes.

Results

The proportions of the groups were 23.6, 69.2, and 7.2%, respectively. As a continuous variable, every 1°C increase in BT was associated with a 21% decrease in 28-day ICU mortality (OR: 0.79, 95% CI: 0.66-0.96, and p = 0.019) and a 23% decrease in in-hospital mortality (OR: 0.77, 95% CI: 0.66-0.91; and p = 0.002). When BT was used as a categorical variable, hypothermia was significantly associated with both 28-day ICU mortality (OR: 1.3, 95% CI: 1.03-1.65; and p = 0.026) and in-hospital mortality (OR: 1.31, 95% CI: 1.07-1.59; and p = 0.008). No statistical differences were observed between 28-day ICU mortality and in-hospital mortality with hyperthermia after adjustment.

Conclusion

The first 24-h mean BT after ICU admission was associated with 28-day ICU and in-hospital mortality in patients with DHF. Hypothermia significantly increased mortality, whereas hyperthermia did not.

Factors affecting mortality after coronary bypass surgery: a scoping review

Objectives

Previous research reports numerous factors of post-operative mortality in patients undergoing isolated coronary artery bypass graft surgery. However, this evidence has not been mapped to the conceptual framework of care improvement. Without such mapping, interventions designed to improve care quality remain unfounded.

Methods

We identified reported factors of in-hospital mortality post isolated coronary artery bypass graft surgery in adults over the age of 19, published in English between January 1, 2000 and December 31, 2019, indexed in PubMed, CINAHL, and EMBASE. We grouped factors and their underlying mechanism for association with in-hospital mortality according to the augmented Donabedian framework for quality of care.

Results

We selected 52 factors reported in 83 articles and mapped them by case-mix, structure, process, and intermediary outcomes. The most reported factors were related to case-mix (characteristics of patients, their disease, and their preoperative health status) (37 articles, 27 factors). Factors related to care processes (27 articles, 12 factors) and structures (11 articles, 6 factors) were reported less frequently; most proposed mechanisms for their mortality effects.

Conclusions

Few papers reported on factors of in-hospital mortality related to structures and processes of care, where intervention for care quality improvement is possible. Therefore, there is limited evidence to support quality improvement efforts that will reduce variation in mortality after coronary artery bypass graft surgery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13019-022-01784-z.

Effect of nurse-initiated forced-air warming blanket on the reduction of hypothermia complications following coronary artery bypass grafting: a randomized clinical trial

AIMS

To evaluate the effect of postoperative forced-air warming (FAW) on the incidence of excessive bleeding (ExB), arrhythmia, acute myocardial infarction (AMI), and blood product transfusion in hypothermic patients following on-pump CABG and compare temperatures associated with the use of FAW and warming with a sheet and wool blanket.

METHODS AND RESULTS

A randomized clinical trial conducted with 200 patients undergoing isolated on-pump CABG from January to November 2018. Patients were randomly assigned into an Intervention Group (IG, FAW, n = 100) and Control Group (CG, sheet and blanket, n = 100). The tympanic temperature of all patients was measured over a 24-h period. ExB was the primary outcome, while arrhythmia, AMI, and blood product transfusion were secondary outcomes. The effect of the interventions on the outcomes was investigated through using bivariate logistic regression, with a level of significance of 5%. The IG was 79% less likely to experience bleeding than the CG [odds ratio (OR) = 0.21, confidence interval (CI) 95% 0.12-0.39, P < 0.001]; the occurrence of AMI in the IG was 94% lower than that experienced by the CG (OR = 0.06, CI 95% 0.01-0.48, P < 0.001); and the IG was also 77% less likely to experience arrhythmia than the CG (OR = 0.23, CI 95% 0.12-0.47, P < 0.001); no difference was found between groups in terms of blood product transfusion (P < 0.279).

CONCLUSIONS

These findings show that FAW can be used following CABG until patients reach normothermia to avoid undesirable clinical outcomes.

TRIAL REGISTRATION

REBeC RBR-5t582g.

Impact of postoperative hypothermia on outcomes after off-pump coronary artery bypass grafting

BACKGROUND

Even though the physiological derangements caused by hypothermia are well described, there is no consensus about its impact on postoperative outcomes. The aim of this study is to assess the effect of postoperative hypothermia on outcomes after off-pump coronary artery bypass surgery.

METHODS

A total of 1979 patients undergoing isolated off-pump coronary artery bypass surgery in a single center in the period 2007-2018 were classified according to their axillary temperature measurement at intensive care unit admission postoperatively to either hypothermic (<36°C) or normothermic (≥36°C). Between-group differences on baseline characteristics and postoperative outcomes were assessed before and after propensity score matching.

RESULTS

Data analysis showed that 582 patients (29.4%) were hypothermic (median temperature 35.5°C) and 1397 patients (70.6%) were normothermic (median temperature 36.4°C). Using propensity score matching, 567 patient pairs were created. Patients with hypothermia exhibited a higher rate of postoperative transfusion of at least three red cell concentrate units (14.3% vs 9%, p = 0.005), a longer intubation duration (median duration, 6 vs 5 h, p < 0.0001), and a longer intensive care unit stay (median stay, 1.6 vs 1.3 days, p = 0.008). There was no difference in reoperation for bleeding, renal replacement therapy, infections, and mortality between the two groups.

CONCLUSIONS

Even though associated with a higher blood transfusion requirement and a slightly longer intensive care unit stay, mild postoperative hypothermia was not associated with a higher morbidity and mortality.

Intraoperative thermal insulation in off-pump coronary artery bypass grafting surgery: a prospective, double blind, randomized controlled, single-center study

Background

About 50% patients who underwent off-pump coronary artery bypass grafting (OPCAB) experienced perioperative hypothermia. Pre-warming and intraoperative infusion of amino acid injection are the most popular perioperative insulation measures in recent years, but neither of them can completely prevent intraoperative hypothermia. The objective is to investigate the effect of preoperative warming and/or intraoperative infusion of amino acid injection on body temperature in patients undergoing OPCAB.

Methods

A prospective, double blind, randomized controlled, single-center study. Seventy-two patients were randomly divided into 4 groups: control group, pre-warming group, amino-acid group and multi-mode group. Pre-warming and multi-mode group were pre-heated with warming blankets and forced-air warming system before induction. After that, amino-acid and multi-mode group were infused with 18-amino acid solution. The perioperative temperature and complications were monitored.

Results

The temperature of control and amino-acid group decreased significantly, but amino-acid group recovered to preoperative level faster. The temperature of pre-warming group was stable, and that in multi-mode group increased at 60 min after the start of surgery. There was a significant difference in temperature at each time, and no difference in the incidence of complications between the groups.

Conclusions

Preoperative warming and/or intraoperative infusion of amino acid injection can effectively reduce hypothermia in OPCAB surgery. Pre-warming before anesthesia is more effective, and the combination of the two methods has the best effect.

Influence of Body Temperature on Bispectral Index-Guided Anesthetic Management in Off-Pump Coronary Artery Bypass Grafting

Background Perioperative hypothermia is not uncommon in surgical patients due to anesthetic-induced inhibition of thermoregulatory mechanisms and exposure of patients to cold environment in the operating rooms. Core temperature reduction up to 35°C is often seen in off-pump coronary artery bypass graft (OP-CABG) surgery. Anesthetic depth can be monitored by using bispectral (BIS) index. The present study was performed to evaluate the influence of mild hypothermia on the anesthetic depth using BIS monitoring and correlation of BIS with end-tidal anesthetic concentration at varying temperatures during OP-CABG.

Materials and Methods In a prospective observational study design in a tertiary care teaching hospital, patients who underwent elective OP-CABG under endotracheal general anesthesia, were included in the study. Standard technique of anesthesia was followed. BIS, nasopharyngeal temperature, and end-tidal anesthetic concentration of inhaled isoflurane was recorded every 10 minutes. The BIS was adjusted to between 45 and 50 during surgery.

Results There were 40 patients who underwent OP-CABG during the study period. The mean age was 51.2 ± 8.7 years, mean body mass index 29.8 ± 2.2, and mean left ventricular ejection fraction was 55.4 ± 4.2%. Anesthetic requirement as guided by BIS between 45 and 50 correlated linearly with core body temperature (r = 0.999; p < 0.001). The mean decrease in the body temperature at the end of 300 minutes was 2.2°C with a mean decrease in end-tidal anesthetic concentration of 0.29%. The reduction in end-tidal anesthetic concentration per degree decrease in temperature was 0.13%. None of the patients reported intraoperative recall.

Conclusion In this study, BIS monitoring was used to guide the delivery concentration of inhaled anesthetic using a targeted range of 45 to 50. BIS monitoring allowed the appropriate reduction of anesthetic dosing requirements in patients undergoing OP-CABG without risk of awareness. There was a significant reduction in anesthetic requirements associated with reduction of core temperature. The routine use of BIS is recommended in OP-CABG to titrate anesthetic requirement during occurrence of hypothermia and facilitate fast-track anesthesia in this patient population.

Retooling of Paper-based Outcome Measures to Electronic Format: Comparison of the NY State Public Risk Model and EHR-derived Risk Models for CABG Mortality

BACKGROUND

Risk adjustment is critical in the comparison of quality of care and health care outcomes for providers. Electronic health records (EHRs) have the potential to eliminate the need for costly and time-consuming manual data abstraction of patient outcomes and risk factors necessary for risk adjustment.

METHODS

Leading EHR vendors and hospital focus groups were asked to review risk factors in the New York State (NYS) coronary artery bypass graft (CABG) surgery statistical models for mortality and readmission and assess feasibility of EHR data capture. Risk models based only on registry data elements that can be captured by EHRs (one for easily obtained data and one for data obtained with more difficulty) were developed and compared with the NYS models for different years.

RESULTS

Only 6 data elements could be extracted from the EHR, and outlier hospitals differed substantially for readmission but not for mortality. At the patient level, measures of fit and predictive ability indicated that the EHR models are inferior to the NYS CABG surgery risk model [eg, c-statistics of 0.76 vs. 0.71 (P<0.001) and 0.76 vs. 0.74 (P=0.009) for mortality in 2010], although the correlation of the predicted probabilities between the NYS and EHR models was high, ranging from 0.96 to 0.98.

CONCLUSIONS

A simplified risk model using EHR data elements could not capture most of the risk factors in the NYS CABG surgery risk models, many outlier hospitals were different for readmissions, and patient-level measures of fit were inferior.

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.

Association Between Postoperative Body Temperature and All-Cause Mortality After Off-Pump Coronary Artery Bypass Graft Surgery: A Retrospective Observational Study

BACKGROUND

Inadvertent perioperative hypothermia is common in patients undergoing off-pump coronary artery bypass grafting (OPCAB). We investigated the association between early postoperative body temperature and all-cause mortality in patients undergoing OPCAB.

METHODS

We reviewed the electronic medical records of 1714 patients who underwent OPCAB (median duration of follow-up, 47 months). Patients were divided into 4 groups based on body temperature at the time of intensive care unit admission after surgery (moderate-to-severe hypothermia, <35.5°C; mild hypothermia, 35.5°C-36.5°C; normothermia, 36.5°C-37.5°C; and hyperthermia, ≥37.5°C). Cox proportional hazards models were used to assess the association between body temperature and all-cause mortality. The association between early postoperative changes in body temperature and all-cause mortality was also assessed by dividing the patients into 4 categories according to the body temperature measured at postoperative intensive care unit admission and the average body temperature during the first 3 postoperative days.

RESULTS

Compared to the normothermia group, the adjusted hazard ratios of all-cause mortality were 2.030 (95% confidence interval, 1.407-2.930) in the moderate-to-severe hypothermia group and 1.445 (95% confidence interval, 1.113-1.874) in the mild hypothermia group. Patients who were hypothermic at postoperative intensive care unit admission but attained normothermia thereafter were at a lower risk of all-cause mortality compared to patients who did not regain normothermia (adjusted hazard ratio, 0.631; 95% confidence interval, 0.453-0.878), while they were still at a higher risk of all-cause mortality than those who were consistently normothermic (adjusted hazard ratio, 1.435; 95% confidence interval, 1.090-1.890).

CONCLUSIONS

Even mild early postoperative hypothermia was associated with all-cause mortality after OPCAB. Patients who regained normothermia postoperatively were at lower risk of all-cause mortality compared to those who did not.

Guideline Implementation: Preventing Hypothermia

The updated AORN "Guideline for prevention of unplanned patient hypothermia" provides guidance for identifying factors associated with intraoperative hypothermia, preventing hypothermia, educating perioperative personnel on this topic, and developing relevant policies and procedures. This article focuses on key points of the guideline, which addresses performing a preoperative assessment for factors that may contribute to hypothermia, measuring and monitoring the patient's temperature in all phases of perioperative care, and implementing interventions to prevent hypothermia. Perioperative RNs should review the complete guideline for additional information and for guidance when writing and updating policies and procedures.

Perioperative Heat Loss Prevention-A Feasibility Trial

Preventing unplanned perioperative hypothermia is crucial. Thermal reflective blankets may reduce heat loss, promote normothermia, increase patient comfort, and decrease cotton blanket expenses. Our purpose was to determine whether a thermal reflective blanket plus one warmed cotton blanket provides better temperature control and thermal comfort than warmed cotton blankets only. We compared two groups of perioperative patients who received a thermal reflective blanket plus one warmed cotton blanket (n = 110) or warmed cotton blankets only (n = 114) for temperature control and comfort, and we evaluated outcomes in the preoperative holding area, the OR, and the postanesthesia care unit. There were no significant differences in patient temperature or comfort between groups. Use of thermal reflective blankets led to significantly reduced use of warmed cotton blankets (t₂₀₉ = -10.51, P < .001), and a cost threshold for clinical adoption was identified. The hospital opted not to purchase thermal reflective blankets because of equivalent performance and minimal cost savings.

A comprehensive literature review on hypothermia and early extubation following coronary artery bypass surgery

PURPOSE

The purpose of this study was to comprehensively review the literature addressing the physiological effects of hypothermia and its association with the appropriate core body temperature for extubation following coronary artery bypass surgery.

METHODS

The electronic databases MEDLINE, CINAHL and Web of Science via OVID were used to identify studies for the literature review. Search words used included 'core temperature', 'arrhythmia', 'cardiac', 'cardiac surgery', 'hypothermia', 'extubation', 'temperature', 'rewarming', and 'shivering'.

RESULTS

The literature search yielded 55 articles that met our inclusion criteria. No studies specifically identified the benefit of extubation at 36.5 ° C. Although temperatures varied, arrhythmias resulting from hypothermia were not reported until core body temperature dropped below 33 ° C.

CONCLUSION

This comprehensive literature review suggests extubation at lower temperatures (between 34 ° C and 36 ° C) may be viable if shivering and other factors known to contribute to myocardial stress can be controlled. These findings offer the possibility of earlier extubation which may promote beneficial health outcomes.

Hypothermia in Adult ICUs: Changing Incidence But Persistent Risk Factor for Mortality

BACKGROUND

This study examined whether hypothermia (< 36.0°C) incidence among critically ill patients varied over time, the determinants of change, and the associated risk for ICU mortality.

METHODS

Interrupted time series analysis among adults admitted to ICUs in Calgary, Canada over 8.5 years. Changes in the incidence of hypothermia within the first 24 hours of ICU admission were modelled using segmented regression.

RESULTS

Among 15,291 first admissions to ICU, hypothermia incidence decreased from 29% to 21% during the study period. Implementation of a new temporal artery thermometer (TAT) was associated with the majority of the decrease in incidence (10%; 95% CI 7.1-13%; P < .0001). However, subgroup analysis revealed important differences between medical and surgical patients. Hypothermia incidence decreased among surgical patients before TAT implementation (0.4% per quarter, 95% CI 0.1-0.7%, P = .009), but not after, whereas in medical patients, the incidence increased after (1.0% per quarter, 95% CI 0.6-1.4%, P < .0001) but not before TAT implementation. Segmented logistic regression suggested that increases in the proportion of patients with non-traumatic neurologic admission diagnoses were associated with hypothermia incidence among medical patients, whereas there was no measurable clinical factor associated with the observed time trends among surgical patients. Hypothermia at ICU admission was independently associated with ICU mortality in medical and surgical patients throughout the entire study.

CONCLUSION

The incidence of hypothermia at ICU admission was dependent on medical versus surgical status, and the method of non-invasive temperature measurement, but was persistently associated with ICU mortality.

The influence of hypothermia on transfusion requirement in patients who received clopidogrel in proximity to off-pump coronary bypass surgery

PURPOSE

Hypothermia adversely affects the coagulation that could be of clinical significance in patients receiving clopidogrel. We evaluated the influence of hypothermia on transfusion requirements in patients undergoing isolated off-pump coronary artery bypass surgery (OPCAB) who continued clopidogrel use within 5 days of surgery.

MATERIALS AND METHODS

Protocol-based, prospectively entered data of 369 patients were retrospectively reviewed. The time-weighted average of intraoperative temperatures and the temperature upon ICU admission (TWA-temp) was assessed. Patients were divided into normothermia (≥36°C, n=224) and hypothermia (<36°C, n=145) group. The transfusion requirement for perioperative blood loss was assessed and compared.

RESULTS

Patients with hypothermia were older and had lower body surface area (BSA) than patients with normothermia. Age and BSA adjusted transfusion requirement was significantly larger in the hypothermia group [patients requiring transfusion: 64% versus 48%, p=0.003; number of units: 0 (0-2) units versus 2 (0-3) units, p=0.002]. In multivariate analysis of predictors of perioperative multiple transfusion requirements, hypothermia was identified as an independent risk factor along with age, female gender, BSA, chronic kidney disease, and congestive heart failure.

CONCLUSION

Hypothermia was associated with increased transfusion requirement in patients undergoing OPCAB who received clopidogrel in proximity to surgery. Considering the high prevalence and the possibility of hypothermia being a modifiable risk factor, aggressive measures should be undertaken to maintain normothermia in those patients.

Adaptations to hibernation in lung surfactant composition of 13-lined ground squirrels influence surfactant lipid phase segregation properties

Pulmonary surfactant lines the entire alveolar surface, serving primarily to reduce the surface tension at the air-liquid interface. Surfactant films adsorb as a monolayer interspersed with multilayers with surfactant lipids segregating into different phases or domains. Temperature variation, which influences lipid physical properties, affects both the lipid phase segregation and the surface activity of surfactants. In hibernating animals, such as 13-lined ground squirrels, which vary their body temperature, surfactant must be functional over a wide range of temperatures. We hypothesised that surfactant from the 13-lined ground squirrel, Ictidomys tridecemlineatus, would undergo appropriate lipid structural re-arrangements at air-water interfaces to generate phase separation, sufficient to attain the low surface tensions required to remain stable at both low and high body temperatures. Here, we examined pressure-area isotherms at 10, 25 and 37°C and found that surfactant films from both hibernating and summer-active squirrels reached their highest surface pressure on the Wilhelmy-Langmuir balance at 10°C. Epifluorescence microscopy demonstrated that films of hibernating squirrel surfactant display different lipid micro-domain organisation characteristics than surfactant from summer-active squirrels. These differences were also reflected at the nanoscale as determined by atomic force microscopy. Such re-arrangement of lipid domains in the relatively more fluid surfactant films of hibernating squirrels may contribute to overcoming collapse pressures and support low surface tension during the normal breathing cycle at low body temperatures.

Intensified thermal management for patients undergoing transcatheter aortic valve implantation (TAVI)

Background

Transcatheter aortic valve implantation via the transapical approach (TAVI-TA) without cardiopulmonary bypass (CPB) is a minimally invasive alternative to open-heart valve replacement. Despite minimal exposure and extensive draping perioperative hypothermia still remains a problem.

Methods

In this observational study, we compared the effects of two methods of thermal management on the perioperative course of core temperature. The methods were standard thermal management (STM) with a circulating hot water blanket under the patient, forced-air warming with a lower body blanket and warmed infused fluids, and an intensified thermal management (ITM) with additional prewarming using forced-air in the pre-operative holding area on the awake patient.

Results

Nineteen patients received STM and 20 were treated with ITM. On ICU admission, ITM-patients had a higher core temperature (36.4 ± 0.7°C vs. 35.5 ± 0.9°C, p = 0.001), required less time to achieve normothermia (median (IQR) in min: 0 (0-15) vs. 150 (0-300), p = 0.003) and a shorter period of ventilatory support (median (IQR) in min: 0 (0-0) vs. 246 (0-451), p = 0.001).

Conclusion

ITM during TAVI-TA reduces the incidence of hypothermia and allows for faster recovery with less need of ventilatory support.

[Preoperative prewarming as a routine measure. First experiences]

BACKGROUND

Despite the broad application of intraoperative warming new studies still show a high incidence of perioperative hypothermia. Therefore a prewarming program in the preoperative holding area was started.

METHODS

The efficacy of the prewarming program was assessed with an accompanying quality assurance check sheet over a period of 3 months.

RESULTS

During the 3 month test period 127 patients were included. The median length from arrival in the holding area to beginning prewarming was 6 min and the average duration of prewarming was 46±38 min. During prewarming the core temperature rose by 0.3±0.4°C to 37.1±0.5°C and decreased to 36.3±0.5°C after induction of anesthesia. At the end of the operation the core temperature was 36.4±0.5°C and 14% of the patients were hypothermic.

CONCLUSION

These data allow 2 conclusions: 1. Prewarming in the holding area is possible with a sufficient duration. 2. Prewarming is highly efficient even when performed over a relatively short duration.