Hypothermia in a surgical intensive care unit

Association of body temperature and mortality in critically ill patients: an observational study using two large databases

BACKGROUND

Body temperature (BT) is routinely measured and can be controlled in critical care settings. BT can impact patient outcome, but the relationship between BT and mortality has not been well-established.

METHODS

A retrospective cohort study was conducted based on the MIMIC-IV (N = 43,537) and eICU (N = 75,184) datasets. The primary outcome and exposure variables were hospital mortality and first 48-h median BT, respectively. Generalized additive models were used to model the associations between exposures and outcomes, while adjusting for patient age, sex, APS-III, SOFA, and Charlson comorbidity scores, temperature gap, as well as ventilation, vasopressor, steroids, and dialysis usage. We conducted subgroup analysis according to ICU setting, diagnoses, and demographics.

RESULTS

Optimal BT was 37 °C for the general ICU and subgroup populations. A 10% increase in the proportion of time that BT was within the 36-38 °C range was associated with reduced hospital mortality risk in both MIMIC-IV (OR 0.91; 95% CI 0.90-0.93) and eICU (OR 0.86; 95% CI 0.85-0.87). On the other hand, a 10% increase in the proportion of time when BT < 36 °C was associated with increased mortality risk in both MIMIC-IV (OR 1.08; 95% CI 1.06-1.10) and eICU (OR 1.18; 95% CI 1.16-1.19). Similarly, a 10% increase in the proportion of time when BT > 38 °C was associated with increased mortality risk in both MIMIC-IV (OR 1.09; 95% CI 1.07-1.12) and eICU (OR 1.09; 95% CI 1.08-1.11). All patient subgroups tested consistently showed an optimal temperature within the 36-38 °C range.

CONCLUSIONS

A BT of 37 °C is associated with the lowest mortality risk among ICU patients. Further studies to explore the causal relationship between the optimal BT and mortality should be conducted and may help with establishing guidelines for active BT management in critical care settings.

Prevalence of Postoperative Hypothermia in the Post-anesthesia Care Unit

Background

Unwanted postoperative hypothermia is an unpleasant event that can cause various complications.

Objectives

As this serious complication and its provoking causes have not been investigated sufficiently, this study was designed and conducted to determine the prevalence of hypothermia and its associated factors in the post-anesthesia care unit after elective surgery.

Methods

Four hundred patients undergoing elective surgeries were enrolled in the present cross-sectional research after termination of surgery and at the time of arrival at the post-anesthesia care unit of Poursina Public University Hospital. The tympanic membrane temperature was measured and recorded at the time of arrival at the post-anesthesia care unit and every 30 minutes after arrival. The required data were collected in a researcher-made checklist and analyzed after entering the SPSS software version 25.

Results

Considering the 5% error, it can be said that the prevalence of hypothermia in patients undergoing elective surgery ranges from 20 to 28% at the time of arrival at the post-anesthesia care unit and 18.5 to 26% 30 minutes after arrival.

Conclusions

More than a quarter of patients experienced hypothermia following elective surgery. Therefore, appropriate treatment and control measures are necessary to manage this complication, particularly in patients with predisposing risk factors and comorbidities.

Efficacy of Cold Tumescent for Prevention of Intraoperative Bleeding in Patients Undergoing Liposuction: A Double-Blind Randomized Controlled Trial-Half-Side Comparison

BACKGROUND

Bleeding, a common intraoperative complication of liposuction, often causes pain and discomfort during recovery. Because of the vasoconstrictive effect of adrenaline in the tumescent solution, bleeding can be reduced; however, reports of postoperative bleeding persist. Cold temperatures also have a vasoconstrictive effect.

OBJECTIVES

This study aimed to determine the efficacy of cold tumescent solution in preventing and reducing intraoperative bleeding.

METHODS

This prospective randomized controlled trial was conducted between June 2018 and June 2019. The liposuction areas in each participant were divided into left and right sides; one side received operative room temperature tumescent solution (25 °C), and the other side received low-temperature tumescent solution (4 °C). The areas of ecchymosis, pain scores, and patient and surgeon satisfaction scores were compared and analyzed.

RESULTS

Ten patients with 36 pairs of liposuction areas were enrolled in the study. Cold tumescent liposuction resulted in a significantly lower lipocrit than was obtained on the standard tumescent side (1.56 ± 0.69 vs 2.92 ± 0.94; P < .001). The ecchymosis area and pain score were significantly lower in the cold tumescent group on days 2, 4, 7, and 14. The satisfaction evaluation scores did not differ between patients and surgeons at 12 months postoperatively.

CONCLUSIONS

The use of cold tumescent anesthesia significantly improved liposuction outcomes by reducing the intraoperative blood loss and the postoperative ecchymosis and pain, with no immediate or short-term complications in low-volume liposuction (<1000 mL) procedures. Furthermore, it generated a standard outcome and good patient satisfaction scores.

LEVEL OF EVIDENCE: 2

Health Technology Assessment for the Prevention of Peri-Operative Hypothermia: Evaluation of the Correct Use of Forced-Air Warming Systems in an Italian Hospital

This study investigates the implications of using a system for the maintenance of normothermia in the treatment of patients undergoing surgery, determining whether the FAW (Forced-Air Warming) systems are more effective and efficient than the non-application of appropriate protocols (No Technology). We conducted Health Technology Assessment (HTA) analysis, using both real-world data and the data derived from literature, assuming the point of view of a medium-large hospital. The literature demonstrated that Inadvertent Perioperative Hypothermia (IPH) determines adverse events, such as surgical site infection (FAW: 3% vs. No Technology: 12%), cardiac events (FAW: 3.5% vs. No Technology: 7.6%) or the need for blood transfusions (FAW: 6.2% vs. No Technology: 7.4%). The correct use of FAW allows a medium saving of 16% per patient to be achieved, compared to the non-use of devices. The Cost Effectiveness Value (CEV) is lower in the hypothesis of FAW: it enables a higher efficacy level with a contextual optimization of patients' path costs. The social cost is reduced by around 30% and the overall hospital days are reduced by between 15% and 26%. The qualitative analyses confirmed the results. In conclusion, the evidence-based information underlines the advantages of the proper use of FAW systems in the prevention of accidental peri-operative hypothermia for patients undergoing surgery.

Postoperative hypothermia following non-cardiac high-risk surgery: A prospective study of temporal patterns and risk factors

Background and objectives

Hypothermia occurs commonly during surgery and can cause postoperative complications. We aimed to describe the characteristics and outcomes of hypothermia in patients undergoing major surgeries.

Methods

This prospective, observational, multicenter study of a nationally representative sample included all patients over 18 years of age admitted to an intensive care unit (ICU). Thirty ICUs were selected randomly at national level. The main outcome measure was the proportion of patients who developed postoperative hypothermia in the first 24 hours of ICU admission. Patients were divided into three groups based on temperature: <35°C, <36°C, and ≥36°C (no hypothermia). Patients’ characteristics, postoperative complications, and risk factors were evaluated in all groups. To verify whether hypothermia was a strong risk factor for postoperative complications, a Kaplan–Meier curve was generated and adjusted using a Cox regression model.

Results

In total, 738 patients had their temperatures measured. The percentage of patients with temperature <35°C (median [Q1-Q3], 34.7°C [34.3–34.9°C]) was 19.1% (95% confidence interval [CI] = 16.1–22.5) and that of patients with temperature <36°C (median [Q1-Q3], 35.4°C [35.0–35.8°C]) was 64% (95% CI = 58.3–70.0). The percentage of surgical complications was 38.9%. Patients with hypothermia were older, had undergone abdominal surgeries, had undergone procedures of longer duration, and had more comorbidities. A postoperative temperature ≤35°C was an independent risk for composite postoperative complications (hazard ratio = 1.523, 95% CI = 1.15–2.0), especially coagulation and infection.

Conclusions

Inadvertent hypothermia was frequent among patients admitted to the ICU and occurred more likely after abdominal surgery, after a long procedure, in elderly patients, and in patients with a higher number of comorbidities. Low postoperative temperature was associated with postoperative complications.

Continued Relevance of Initial Temperature Measurement in Trauma Patients

OBJECTIVES

Hypothermia occurs in 30-50% of severely injured trauma patients and is associated with multiple metabolic derangements and worsened outcomes. However, hypothermia continues to be under-diagnosed which leads to inadequate triage and treatment in trauma patients. Our study set out to determine if hypothermia is an independent predictor of mortality in trauma patients.

METHODS

We retrospectively reviewed data of all trauma activation patients over a 5-year period. Data were collected on patient demographics, initial core temperature, Glasgow Coma Scale (GCS) on presentation, and injury severity score (ISS). Patients were then stratified into groups based on presenting temperature, ISS, and GCS. Outcomes compared were mortality, blood products received, and intensive care unit (ICU) length of stay. Correlations and logistic regression were used to test the hypotheses.

RESULTS

Survival and temperature data were reviewed on 15,567 patients. Initial temperature was not significantly associated with ICU length of stay or blood products transfused (P = .21 and P = .08, respectively). However, odds ratio of mortality in hypothermic patients (<35°C) compared to normothermic patients (35-39°C) was 3.95 (95% CI 2.90-5.41). When controlling for GCS and ISS, separately, temperature remained an independent predictor of mortality.

CONCLUSIONS

Hypothermia is an independent risk factor for mortality in trauma patients. It remains crucial to obtain accurate presenting temperatures in trauma patients in order to triage and treat hypothermia. Based on our data, obtaining core temperatures and rapidly treating hypothermia continues to be a vital part of the secondary survey of trauma patients.

A prognostic model for 1-month mortality in the postoperative intensive care unit

PURPOSES

Recognizing which patients admitted postsurgically to the intensive care unit (ICU) are at greater risk of mortality assists medical staff to identify who will benefit most from the care. We developed a prediction model for the 1-month mortality of postsurgical ICU patients.

METHODS

From May, 2019 to May, 2020, we conducted a prospective cohort study in the postsurgical ICU of a teaching hospital affiliated with our University of Medical Sciences. The outcome was death within 1 month of admission and the predictors were a variety of anthropometric and clinical features. The subjects of this analysis were 805 consecutive adult postsurgical patients with a mean (SD) age of 54.8 (18.9) years.

RESULTS

Overall, the resulted logistic model was well-fitted [χ² (26) = 772.097, p < 0.001, Nagelkerke R² = 0.814] accurate (88%), and specific (92%). The adjusted odds ratio for body temperature was 0.51, p < 0.001. Patients with comorbidities and those undergoing multiple operations were at a greater risk of mortality, odds = 10.00 and 10.65 (both p < 0.001).

CONCLUSIONS

Higher body temperature at the time of postoperative ICU admission is a protective factor against 1-month mortality. Our study found that patients with several comorbidities and those who have undergone multiple operations are at a greater risk of a poor outcome.

The related factors and countermeasures of hypothermia in patients during the anesthesia recovery period

OBJECTIVE

This research aims to explore and analyze the risk factors that lead to hypothermia in patients in the post-anesthesia care unit (PACU) and to investigate the heat preservation effects of the various heat preservation measures.

METHODS

A total of 224 patients who entered the PACU from February 2018 to October 2018 after anesthesia surgery in our hospital were recruited as the research cohort. Among them, 46 had hypothermia and 178 did not. The patients' general and surgical data were recorded, and the risk factors for hypothermia in the PACU patients were analyzed using logistic regression. Another 68 hypothermia patients admitted to the PACU in our hospital were also recruited for this study. The patients in the routine group (RG) were insulated using quilts, while those in the observation group (OG) were insulated using inflatable warming blankets. The heat preservation effects of the two heat preservation methods on the PACU patients were compared.

RESULTS

Age >60 years old, an intraoperative infusion volume >1500 ml, an intraoperative blood loss >300 ml, major surgery, and an operation time >2 h were the risk factors for hypothermia in the PACU patients. The heat preservation times, the PACU retention times, and the patients' awake times in the OG were shorter than they were in the RG, and the incidence of complications related to hypothermia in the OG was lower than it was in the RG. In addition, the degree of satisfaction in the OG was higher than it was in the RG.

CONCLUSION

Age >60 years old, an intraoperative infusion volume >1500 ml, an intraoperative blood loss >300 ml, major surgery, and an operation time >2 h are risk factors for hypothermia in PACU patients. Inflatable warming blankets have a better heat preservation effect and bring higher patient satisfaction than traditional quilts.

Prevention of infection in primary THA and TKA

Rates of peri-prosthetic joint infection (PJI) in primary total hip and total knee arthroplasty range between 0.3% and 1.9%, and up to 10% in revision cases. Significant morbidity is associated with this devastating complication, the economic burden on our healthcare system is considerable, and the personal cost to the affected patient is immeasurable.

The risk of surgical site infection (SSI) and PJI is related to surgical factors and patient factors such as age, body mass index (BMI), co-morbidities, and lifestyle. Reducing the risk of SSI in primary hip and knee arthroplasty requires a multi-faceted strategy including pre-operative patient bacterial decolonization, screening and avoidance of anaemia, peri-operative patient warming, skin antisepsis, povidone-iodine wound lavage, and anti-bacterial coated sutures.

This article also considers newer concepts such as the influence of bearing surfaces on infection risk, as well as current controversies such as the potential effects of blood transfusion, laminar flow, and protective hoods and suits, on infection risk.

Cite this article: EFORT Open Rev 2020;5:604-613. DOI: 10.1302/2058-5241.5.200004

Effect of Thermal Insulation on Image Quality and Radiation Dose in Polytrauma Computed Tomography

PURPOSE

Unintentional drop in body temperature in trauma victims is an independent risk factor for mortality. We aimed to assess the impact of thermal insulation on image quality and radiation dose in polytrauma computed tomography (CT).

METHODS

Thirteen different insulating covers were used to wrap CT phantoms. Images were assessed subjectively at a radiological workstation and analyzed digitally with dedicated software evaluating the noise intensity, spatial resolution, and image homogeneity. The radiation dose was measured using a dosimeter.

RESULTS

Most materials did not cause significant artifacts apart from 2 heating pads. Although the radiation dose was increased by the majority of insulating covers (up to 64.66%), certain covers decreased the absorbed radiation (up to -7.35%).

CONCLUSIONS

The majority of insulating systems do not cause artifacts in CT scans. When using covers with self-heating warmers, removing the heating pad is suggested due to the risk of considerable artifacts appearing. Certain insulating covers may increase or decrease the radiation dose.

Prevalence of hypothermia on admission to recovery room remains high despite a large use of forced-air warming devices: Findings of a non-randomized observational multicenter and pragmatic study on perioperative hypothermia prevalence in France

BACKGROUND

Despite the availability of effective warming systems, the prevalence of hypothermia remains high in patients undergoing surgery. Occurrence of perioperative hypothermia may influence the rate of postoperative complications. Recommendations for the prevention of inadvertent perioperative hypothermia have been developed and are effective to reduce the frequency of perioperative hypothermia when professionals comply with. French Society of Anesthesiology (SFAR) decided to promote guidelines for the prevention of inadvertent hypothermia, and to conduct beforehand a pragmatic assessment of the prevalence of hypothermia in France. The hypothesis was that the rate of hypothermic patients (Tc<36°C) admitted to the RR remains high (around 50%), and that was the consequence of a warming device underutilization and/or was related to the type of health facilities.

METHODS

An observational, prospective and multi-centric study was conducted in France between October 2014 and May 2016 among patients over 45 years undergoing non-cardiac, non-outpatient surgery with anesthesia lasting >30 minutes in 52 centers. Patients undergoing pulmonary or proctologic surgery and those having non-invasive procedures performed under general anesthesia (for example, digestive endoscopy) were excluded from our study. Patients being operated under plexus anesthesia alone, surgeries involving hemorrhaging or infection, and patients presenting at least one organ failure were also excluded. The primary endpoint was the percentage of patients with a core temperature (Tc) <36°C on admission to the recovery room (RR).

RESULTS

Among 893 subjects (median age 66.9 years), prevalence of hypothermia on admission to the RR was 53.5%. At least one warming system was used for 90.4% of the patients. Identified risk factors for Tc<36°C included age≥70 years (OR = 1.41 [CI95%: 1.02-1.94]), duration of anesthesia from 1 to 2 hours (OR = 1.94 [CI95%: 1.04-3.64]) and a decrease in Tc of >0.5°C between anesthesia induction and surgical incision (OR = 1.82 [CI95%: 1.15-2.89]). Only a combination of pre-warming and intraoperative warming prevented a Tc<36°C (OR = 0.48 [CI95%: 0.24-0.96]).

CONCLUSIONS

The prevalence of hypothermia among patients admitted to the RR remains high. Our results suggest that only the combination of pre-warming and intraoperative warming significantly decreases it.

Influence of oral premedication and prewarming on core temperature of cardiac surgical patients: a prospective, randomized, controlled trial

Background

Perioperative hypothermia is still very common and associated with numerous adverse effects. The effects of benzodiazepines, administered as premedication, on thermoregulation have been studied with conflicting results. We investigated the hypotheses that premedication with flunitrazepam would lower the preoperative core temperature and that prewarming could attenuate this effect.

Methods

After approval by the local research ethics committee 50 adult cardiac surgical patients were included in this prospective, randomized, controlled, single-centre study with two parallel groups in a university hospital setting. Core temperature was measured using a continuous, non-invasive zero-heat flux thermometer from 30 min before administration of the oral premedication until beginning of surgery. An equal number of patients was randomly allocated via a computer-generated list assigning them to either prewarming or control group using the sealed envelope method for blinding. The intervention itself could not be blinded. In the prewarming group patients received active prewarming using an underbody forced-air warming blanket. The data were analysed using Student’s t-test, Mann-Whitney U-test and Fisher’s exact test.

Results

Of the randomized 25 patients per group 24 patients per group could be analysed. Initial core temperature was 36.7 ± 0.2 °C and dropped significantly after oral premedication to 36.5 ± 0.3 °C when the patients were leaving the ward and to 36.4 ± 0.3 °C before induction of anaesthesia. The patients of the prewarming group had a significantly higher core temperature at the beginning of surgery (35.8 ± 0.4 °C vs. 35.5 ± 0.5 °C, p = 0.027), although core temperature at induction of anaesthesia was comparable. Despite prewarming, core temperature did not reach baseline level prior to premedication (36.7 ± 0.2 °C).

Conclusions

Oral premedication with benzodiazepines on the ward lowered core temperature significantly at arrival in the operating room. This drop in core temperature cannot be offset by a short period of active prewarming.

Trial registration

This trial was prospectively registered with the German registry of clinical trials under the trial number DRKS00005790 on 20th February 2014.

Enhanced recovery after surgery in emergency colorectal surgery: Review of literature and current practices

Enhanced recovery after surgery (ERAS), a multidisciplinary program designed to minimize stress response to surgery and promote the recovery of organ function, has become a standard of perioperative care for elective colorectal surgery. In an elective setting, ERAS program has consistently been shown to decrease postoperative complication, reduce length of hospital stay, shorten convalescence, and lower healthcare cost. Recently, there is emerging evidence that ERAS program can be safely and effectively applied to patients with emergency colorectal conditions such as acute colonic obstruction and intraabdominal infection. This review comprehensively covers the concept and application of ERAS program for emergency colorectal surgery. The outcomes of ERAS program for this emergency surgery are summarized as follows: (1) The ERAS program was associated with a lower rate of overall complication and shorter length of hospital stay - without increased risks of readmission, reoperation and death after emergency colorectal surgery; and (2) Compliance with an ERAS program in emergency setting appeared to be lower than that in an elective basis. Moreover, scientific evidence of each ERAS item used in emergency colorectal operation is shown. Perspectives of ERAS pathway in emergency colorectal surgery are addressed. Finally, evidence-based ERAS protocol for emergency colorectal surgery is presented.

Association between perioperative hypothermia and patient outcomes after thoracic surgery: A single center retrospective analysis

Hypothermia due to anaesthetic-induced impairment of thermoregulatory control and exposure to a cool environment is common in surgical patients. Peripheral vasodilation due to neuroaxial blockade may aggravate hypothermia. There is few data on perioperative hypothermia in patients undergoing thoracic surgery under combined general and regional anesthesia. We reviewed all thoracic surgical patients between 2006 and 2011 to determine the incidence and extent of hypothermia with or without an epidural anesthesia and evaluated its effect.Around 339 patients underwent lung resection procedures with intraoperative forced-air warming: 197 with general and epidural anesthesia (GA + EPI), 199 with general anesthesia alone (GA). Statistical analyses were performed to determine the association between hypothermia (T < 36°C) and transfusion requirements, length of stay (LOS) in the intensive care unit (ICU), hospital LOS, and in hospital mortality.The overall incidence of hypothermia was 64.3%. Multivariate regression analysis revealed three significant risk factors for the development of hypothermia: long induction time (P = .011), small body surface area (P = .003), and application of more fluid intraoperatively (P < .001). Factors determining the extent of hypothermia were: receiving an open thoracotomy (P = .009), placement and use of an epidural catheter (P = .002), and a lower body mass index (BMI) (P < .001). Additional epidural anesthesia reduced core temperature by 0.26°C (95% CI -0.414 to -0.095°C, P < .05). There was no difference in transfusion requirements, ICU LOS or mortality between both groups. Hospital LOS was longer in patients with hypothermia.More than half of all thoracic patients suffered from hypothermia. A long induction time, small body surface area, and large intraoperative fluid application were independent risk factors for the development of perioperative hypothermia. Additional epidural anesthesia to general anesthesia did not increase the incidence of hypothermia but decreased body core temperature to an-albeit not clinically significant-degree. Patients scheduled for thoracic surgery will probably benefit from an additional period of prewarming prior to induction to reduce the high incidence of perioperative hypothermia.

The impact of operative time and hypothermia in acute burn surgery

BACKGROUND

Prolonged operative time and intraoperative hypothermia are known to have deleterious effects on surgical outcomes. Although millions of burn injuries undergo operative treatment globally every year, there remains a paucity of evidence to guide perioperative practice in burn surgery. This study evaluated associations between hypothermia and operative time on post-operative complications in acute burn surgery.

METHOD

A historical cohort study from January 1, 2006 to October 31, 2015 was completed at an American Burn Association verified burn centre. 1111 consecutive patients undergoing acute burn surgery were included, and 2171 surgeries were analyzed. Primary outcomes included post-operative complications, defined a priori as either infectious or noninfectious. Statistical analysis was undertaken using a modified Poisson model for relative risk, adjusted for total body surface area, inhalation injury, co-morbidities, substance abuse, and age.

RESULTS

The mean operative time was 4.4h (SD 3.7-4.7h; range 0.58-11h), and 18.6% of patients became hypothermic intra-operatively. Operative time was independently associated with the incidence of hypothermia (p<0.05), and both infectious (RR1.5; 1.2-1.9, p<0.0004) and non-infectious complications (RR2.3; 1.3-4.1, p<0.0066). In patients with major burns (TBSA≥20%), hypothermia predisposed to infectious (RR1.3; 1.1-1.5, p<0.0017) and non-infectious complications (RR1.7; 1.2-2.5; p<0.0049). Risk stratification revealed that hypothermic patients with major burns undergoing prolonged surgery had an increased risk of both infectious (RR1.4; 1.1-1.7, p<0.0068) and non-infectious complications (RR1.8; 1.1-3.0, p<0.0132) when compared with those without these risk factors.

CONCLUSIONS

Patients who undergo prolonged surgeries and become hypothermic are more likely to develop complications. We therefore advocate for diligent adherence to strategies to prevent hypothermia and recommend limiting operative time in clinical circumstances where intraoperative measures are unlikely to adequately prevent hypothermia.

Inadvertent hypothermia and mortality in critically ill adults: Systematic review and meta-analysis

OBJECTIVE

Considering that inadvertent hypothermia (IH) is common in Intensive Care Unit (ICU) patients and can be followed by severe complications, this systematic review identified, appraised and synthesised the published literature about the association between IH and mortality in adults admitted to the ICU.

DATA SOURCES

By using key terms, literature searches were conducted in Pubmed, CINAHL, Cochrane Library, Web of Science and EMBASE.

REVIEW METHODS

According to PRISMA guidelines, articles published between 1980-2016 in English-language, peer-reviewed journals were considered. IH was defined as core temperature of <36.5°C or lower, present on ICU admission or manifested during ICU stay. Outcome measure included ICU, hospital or 28-day mortality. Selected cohort studies were evaluated with the Newcastle-Ottawa Scale. Extracted data were summarised in tables and synthesised qualitatively and quantitatively, with adjusted odds ratios (ORs) for mortality being combined in meta-analyses.

RESULTS

Eighteen observational studies met inclusion criteria. All of them had high methodological quality. In twelve out of fifteen studies, unadjusted mortality was significantly higher in hypothermic patients compared to non-hypothermic ones. Likewise, in thirteen out of sixteen studies, IH or lowest core temperature was independently associated with significantly higher mortality. High severity and long duration of IH were also associated with higher mortality. Mortality was significantly higher in patients with core temperature <36.0°C (pooled OR 2.093, 95% CI 1.704-2.570), and in those with core temperature <35.0°C (pooled OR 2.945, 95% CI 2.166-4.004).

CONCLUSIONS

These findings indicate that IH predicts mortality in critically ill adults and pose suspicion that this may contribute to adverse patient outcome.

Forced-Air Warming Provides Better Control of Body Temperature in Porcine Surgical Patients

Background: Maintaining normothermia during porcine surgery is critical in ensuring subject welfare and recovery, reducing the risk of immune system compromise and surgical-site infection that can result from hypothermia. In humans, various methods of patient heating have been demonstrated to be useful, but less evaluation has been performed in techniques to prevent hypothermia perioperatively in pigs. Methods: We compared body temperature regulation during surgery before and after modification of the ambient temperature of the operating laboratories. Three different methods of heating were then compared; a standard circulating water mattress, a resistive fabric blanket, and a forced hot air system. The primary measure was percentage of temperature readings outside a specification range of 36.7–40.0 °C. Results: Tighter control of the ambient temperature while using a circulating water mattress reduced the occurrence of out-of-specification body temperature readings from 20.8% to 5.0%, with most of these the result of hypothermia. Use of a resistive fabric blanket further reduced out-of-specification readings to 1.5%, with a slight increase in the occurrence of hyperthermia. Use of a forced air system reduced out-of-specification readings to less 0.1%. Conclusions: Maintenance of normothermia perioperatively in pig can be improved by tightly controlling ambient temperatures. Use of a resistive blanket or a forced air system can lead to better control than a circulating water mattress, with the forced air system providing a faster response to temperature variations and less chance of hyperthermia.

Unexpectedly high incidence of hypothermia before induction of anesthesia in elective surgical patients

STUDY OBJECTIVE

Perioperative hypothermia is a frequently observed phenomenon of general anesthesia and is associated with adverse patient outcome. Recently, a significant influence of core temperature before induction of anesthesia has been reported. However, there are still little existing data on core temperature before induction of anesthesia and no data regarding potential risk factors for developing preoperative hypothermia. The purpose of this investigation was to estimate the incidence of hypothermia before anesthesia and to determine if certain factors predict its incidence.

DESIGN/SETTING/PATIENTS

Data from 7 prospective studies investigating core temperature previously initiated at our department were analyzed. Patients undergoing a variety of elective surgical procedures were included.

INTERVENTIONS/MEASUREMENTS

Core temperature was measured before induction of anesthesia with an oral (314 patients), infrared tympanic (143 patients), or tympanic contact thermometer (36 patients). Available potential predictors included American Society of Anesthesiologists status, sex, age, weight, height, body mass index, adipose ratio, and lean body weight. Association with preoperative hypothermia was assessed separately for each predictor using logistic regression. Independent predictors were identified using multivariable logistic regression.

MAIN RESULTS

A total of 493 patients were included in the study. Hypothermia was found in 105 patients (21.3%; 95% confidence interval, 17.8%-25.2%). The median core temperature was 36.3°C (25th-75th percentiles, 36.0°C-36.7°C). Two independent factors for preoperative hypothermia were identified: male sex and age (>52years).

CONCLUSIONS

As a consequence of the high incidence of hypothermia before anesthesia, measuring core temperature should be mandatory 60 to 120minutes before induction to identify and provide adequate treatment to hypothermic patients.

A recommended early goal-directed management guideline for the prevention of hypothermia-related transfusion, morbidity, and mortality in severely injured trauma patients

Hypothermia is present in up to two-thirds of patients with severe injury, although it is often disregarded during the initial resuscitation. Studies have revealed that hypothermia is associated with mortality in a large percentage of trauma cases when the patient's temperature is below 32 °C. Risk factors include the severity of injury, wet clothing, low transport unit temperature, use of anesthesia, and prolonged surgery. Fortunately, associated coagulation disorders have been shown to completely resolve with aggressive warming. Selected passive and active warming techniques can be applied in damage control resuscitation. While treatment guidelines exist for acidosis and bleeding, there is no evidence-based approach to managing hypothermia in trauma patients. We synthesized a goal-directed algorithm for warming the severely injured patient that can be directly incorporated into current Advanced Trauma Life Support guidelines. This involves the early use of warming blankets and removal of wet clothing in the prehospital phase followed by aggressive rewarming on arrival at the hospital if the patient's injuries require damage control therapy. Future research in hypothermia management should concentrate on applying this treatment algorithm and should evaluate its influence on patient outcomes. This treatment strategy may help to reduce blood loss and improve morbidity and mortality in this population of patients.

[Prewarming. Yesterday's luxury, today's minimum requirement]

Prewarming is a useful and effective measure to reduce perioperative hypothermia. Due to §23(3) of the German Infektionsschutzgesetz (Gesetz zur Verhütung und Bekämpfung von Infektionskrankheiten beim Menschen, Infection Act, act on protection and prevention of infectious diseases in man) and the recommendations of the Hospital Hygiene and Infection Prevention Committee of the Robert Koch Institute, implementation of prewarming is clearly recommended. There are several technically satisfactory and practicable devices available allowing prewarming on the normal hospital ward, in the preoperative holding area or in the induction room of the operating theater (OR) The implementation of prewarming requires additional equipment and training of staff. Using a locally adapted concept for the implementation of prewarming does not lead to inefficiency in the perioperative process. In contrast, the implementation can help to achieve stable arrival times for patients in the OR.

Survey on Postoperative Hypothermia Incidence In Operating Theatres of Kocaeli University

OBJECTIVE

Hypothermia is a common problem in anaesthetized patients and an important risk factor for mortality and morbidity. Our aim was to identify the incidence of hypothermia in our operating theatres. We also aimed to find the circumstances to which hypothermia could be related.

METHODS

After obtaining the ethics committee approval and informed patient consent, patients with operation times longer than 30 minutes were included into the study for a one month period. Demographical data of the patients, type and duration of surgeries, temperatures measured pre and postoperatively from the tympanic membrane with an infrared thermometer were recorded. Temperatures below 35°C were accepted as hypothermia.

RESULTS

A total number of 564 patients were enrolled to the study (305 women and 259 men). The ages of patients varied from 1 month to 84 years (mean 38.5±20.7). Hypothermia incidence was calculated as 45.7%. When the factors related to hypothermia were considered, age, type and duration of surgery and amount of fluids administered were found to be significant contributors to the development of hypothermia (p<0.05).

CONCLUSION

Postoperative hypothermia is a common problem in our clinic. Therefore, we suggest that temperature monitoring and patient warming should be a routine procedure during anaesthesia management.

[Efficacy of a novel warming blanket: prospective randomized trial]

BACKGROUND

Perioperative hypothermia is a common complication of general anesthesia and occurs in up to 50 % of patients during ear, nose and throat (ENT) surgery. In this prospective, randomized controlled study the hypothesis that a new conductive warming blanket (Barrier® EasyWarm®, Mölnlycke Health Care Erkrath, Germany) is better in reducing the incidence of perioperative hypothermia in ENT surgery than insulation with a conventional hospital duvet alone was tested.

MATERIALS AND METHODS

After approval of the local ethics committee and written informed consent 80 patients with a planned procedure time between 1 and 3 h were recruited. Anesthesia was induced and maintained using propofol, remifentanil and rocuronium and the core temperature was measured using an esophageal temperature probe. Patients in the study group were warmed at least 30 min prior to induction of anesthesia using the novel warming blanket (Barrier® EasyWarm®) and patients in the control group were insulated with a standard hospital duvet. Data were tested using Fisher's exact test, Student's t-test or the Mann-Whitney U-test as appropriate. Time-dependent changes in core temperature were evaluated using repeated measures analysis of variance (ANOVA) and post hoc Scheffé's test. Results are expressed as mean ± SD or as median and interquartile range (IQR) as appropriate. A p < 0.05 was considered to be statistically significant.

RESULTS

The ANOVA did not identify a significantly higher core temperature in the study group at any time point. Furthermore, Fisher's exact test showed no differences in the incidence of intraoperative (12 out of 29 versus 10 out of 32 patients, p = 0.44) or postoperative hypothermia (12 out of 29 versus 9 out of 32 patients, p = 0.30) between the groups. No adverse effects were observed.

CONCLUSIONS

In the studied patient group the new conductive warming blanket (Barrier® EasyWarm®) showed no superiority compared to conventional thermal insulation alone.

Retrospective study of the prevalence of postanaesthetic hypothermia in dogs

The anaesthetic records of 1525 dogs were examined to determine the prevalence of postanaesthetic hypothermia, its clinical predictors and consequences. Temperature was recorded throughout the anaesthesia. At the end of the procedure, details coded in were: hyperthermia (>39.50°C), normothermia (38.50°C-39.50°C), slight (38.49°C-36.50°C), moderate (36.49°C-34.00°C) and severe hypothermia (<34.00°C). Statistical analysis consisted of multiple regression to identify the factors that are associated with the temperature at the end of the procedure. Before premedication, the temperature was 38.7 ± 0.6°C (mean ± sd). At 60, 120 and 180 minutes from induction, the temperature was 36.7 ± 1.3°C, 36.1 ± 1.4°C and 35.8 ± 1.5°C, respectively. The prevalence of hypothermia was: slight, 51.5 per cent (95 per cent CI 49.0 to 54.0 per cent); moderate, 29.3 per cent (27.1-31.7 per cent) and severe: 2.8% (2.0-3.7%). The variables that associated with a decrease in the temperature recorded at the end of the anaesthesia were: duration of the preanesthetic time, duration of the anaesthesia, physical condition (ASA III and ASA IV dogs showed lower temperatures than ASA I dogs), the reason for anaesthesia (anaesthesia for diagnostic procedures or thoracic surgery reduce the temperature when compared with minor procedures), and the recumbency during the procedure (sternal and dorsal recumbencies showed lower temperatures than lateral recumbency). The temperature before premedication and the body surface (BS) were associated with a higher temperature at the end of the anaesthesia, and would be considered as protective factors.

[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.

[Perioperative thermal management]

Perioperative hypothermia can influence clinical outcome negatively. It triples the incidence of adverse myocardial outcomes, significantly increases perioperative blood loss, significantly augments allogenic transfusion requirements, and increases the incidence of surgical wound infections. The major causes are redistribution of heat from the core of the body to the peripheral tissues and a negative heat balance. Adequate thermal management includes preoperative and intraoperative measures. Preoperative measures, e.g., prewarming, enhance heat content of the peripheral tissues, thereby reducing redistribution of heat from the core to the peripheral tissues after induction of anesthesia. Intraoperative measures are active skin surface warming of a large body surface area with conductive or convective warming systems. Intravenous fluids should be warmed when large volumes of more than 500-1000 ml/h are required. The body surfaces that cannot be actively warmed should be insulated. Airway humidification and conductive warming of the back are less efficient.

The thermodynamics of general anesthesia

It is known that the action of general anesthetics is proportional to their partition coefficient in lipid membranes (Meyer-Overton rule). This solubility is, however, directly related to the depression of the temperature of the melting transition found close to body temperature in biomembranes. We propose a thermodynamic extension of the Meyer-Overton rule, which is based on free energy changes in the system and thus automatically incorporates the effects of melting point depression. This model accounts for the pressure reversal of anesthesia in a quantitative manner. Further, it explains why inflammation and the addition of divalent cations reduce the effectiveness of anesthesia.

Survey on intraoperative temperature management in Europe

BACKGROUND AND OBJECTIVES

Inadvertent perioperative hypothermia causes serious morbidity in surgical patients. However, recent reports suggest that patients might still be hypothermic after elective surgery. We thus surveyed intraoperative temperature monitoring and management practices in Europe.

METHODS

Postal survey of 801 representative hospitals from 17 European countries on the same day. The questions addressed the number of surgical procedures and type of anaesthesia performed, mode and site of temperature monitoring and method of patient warming. Mean and standard error of the mean or count and percentage were calculated. The t-test or contingency table analysis with the Fisher's exact test were used.

RESULTS

Eight thousand and eighty-three surgical procedures were assessed from 316 responding hospitals (39.4%). Overall, patient temperature monitored in 19.4% and 38.5% of the patients were actively warmed. Under general anaesthesia, body temperature was monitored in 25% and during regional anaesthesia in 6%, P = 0.0005. Nasopharyngeal temperature was most often taken under general anaesthesia, while tympanic temperature was preferred during regional anaesthesia. Under general anaesthesia, 43% of patients were actively warmed as compared to 28% with regional anaesthesia, P = 0.0005. Forced-air warming was the method of choice for both general and regional anaesthesia.

CONCLUSIONS

Intraoperative temperature monitoring is still uncommon and hence active patient warming is not a standard of care in Europe. Awareness of perioperative hypothermia is critical to its prevention, and thus temperature monitoring is a pre-requisite. The objective is to maintain normothermia in patients throughout surgery. A European practice guideline for perioperative patient temperature management is warranted.