Resistive-polymer versus forced-air warming: comparable efficacy in orthopedic patients

Construction of a Risk Prediction Model for Intraoperative Hypothermia in Patients Undergoing Lower Extremity Joint Replacement

PURPOSE

To investigate the influencing factors of intraoperative hypothermia (IOH) in patients undergoing total joint arthroplasty (TJA) of the lower extremities, establish a risk prediction model, and test the effect of application.

DESIGN

A prospective, observational study was conducted.

METHODS

Patients who underwent total knee arthroplasty and total hip arthroplasty from June 2020 to December 2021 were prospectively analyzed. According to the occurrence of IOH, patients were divided into the IOH group (temperature less than 36 °C) and non-IOH group (temperature ≥36 °C). We collected demographic, anesthesia, and surgical data for both groups to identify risk factors for IOH and develop a predictive model. The model's goodness of fit was assessed using the Hosmer-Lemeshow test, and its predictive efficacy was evaluated using the receiver operating characteristic curve.

FINDINGS

A total of 258 patients were included in this study, with 79 patients in the IOH group and 179 patients in the non-IOH group. Logistic regression analysis showed that American Society of Anesthesiologists' grade, blood loss, and duration of surgery were independent risk factors for IOH in lower extremity TJA patients. Hosmer-Lemeshow test P = .803, area under receiver operating characteristic curve was 0.846, Youden index was 0.490, sensitivity was 65.4%, specificity was 83.6%. In the external validation cohort, the application accuracy of the model was 83.3%.

CONCLUSIONS

The prediction model established in this study is suitable for the risk assessment of IOH in TJA patients with good prediction effect, which can provide a tool for clinical medical staff to identify high-risk populations preoperatively.

Barriers and facilitators to evidence-based perioperative hypothermia management for orthopaedic patients: A systematic review

AIM

To assess barriers and facilitators to the implementation of guidelines for the prevention of inadvertent perioperative hypothermia in orthopaedic patients.

DESIGN

Systematic review.

DATA SOURCES

Nine databases: PubMed, Embase, CINAHL, Cochrane CENTRAL, PsycINFO, ProQuest Dissertations and Theses, Scopus, Web of Science and Trip Clinical Evidence Database.

METHODS

Primary studies published in English between January 2008 to July 2022 were screened. Study selection, quality assessment, and data extraction were completed independently by researchers. Data were extracted using the Consolidated Framework for Implementation Research and mapped to the Expert Recommendations for Implementing Change strategies.

RESULTS

Eighty-seven studies were included in the review. The most frequently reported barriers and facilitators related to evidence strength, relative advantage, and cost of implementing perioperative hypothermia prevention guidelines. The top four ERIC strategies were: Identify and prepare champions; Conduct educational meetings; Assess for readiness and identify barriers and facilitators; and Inform local opinion leaders.

CONCLUSION

This review provides synthesized evidence regarding barriers and facilitators to perioperative hypothermia guidelines for patients undergoing orthopaedic surgery.

IMPLICATIONS FOR THE PROFESSION AND PATIENT CARE

Our work provides theory guided strategies to promote implementation of perioperative hypothermia prevention to assist nurses caring for patients undergoing orthopaedic surgery.

IMPACT

Findings provide professionals caring for patients undergoing orthopaedic surgery with theory-informed strategies to improve perioperative hypothermia prevention. Reducing perioperative hypothermia will improve outcomes for patients undergoing orthopaedic surgery.

REPORTING METHOD

The review is reported according to the Preferred Reporting Items for Systematic Reviews and Meta-Analyses 2020.

NO PATIENT OR PUBLIC CONSULTATION

Due to the study design, no patient or public consultation took place.

European Society of Anaesthesiology and Intensive Care consensus document on sustainability: 4 scopes to achieve a more sustainable practice

Climate change is a defining issue for our generation. The carbon footprint of clinical practice accounts for 4.7% of European greenhouse gas emissions, with the European Union ranking as the third largest contributor to the global healthcare industry's carbon footprint, after the United States and China. Recognising the importance of urgent action, the European Society of Anaesthesiology and Intensive Care (ESAIC) adopted the Glasgow Declaration on Environmental Sustainability in June 2023. Building on this initiative, the ESAIC Sustainability Committee now presents a consensus document in perioperative sustainability. Acknowledging wider dimensions of sustainability, beyond the environmental one, the document recognizes healthcare professionals as cornerstones for sustainable care, and puts forward recommendations in four main areas: direct emissions, energy, supply chain and waste management, and psychological and self-care of healthcare professionals. Given the urgent need to cut global carbon emissions, and the scarcity of evidence-based literature on perioperative sustainability, our methodology is based on expert opinion recommendations. A total of 90 recommendations were drafted by 13 sustainability experts in anaesthesia in March 2023, then validated by 36 experts from 24 different countries in a two-step Delphi validation process in May and June 2023. To accommodate different possibilities for action in high- versus middle-income countries, an 80% agreement threshold was set to ease implementation of the recommendations Europe-wide. All recommendations surpassed the 80% agreement threshold in the first Delphi round, and 88 recommendations achieved an agreement >90% in the second round. Recommendations include the use of very low fresh gas flow, choice of anaesthetic drug, energy and water preserving measures, "5R" policies including choice of plastics and their disposal, and recommendations to keep a healthy work environment or on the importance of fatigue in clinical practice. Executive summaries of recommendations in areas 1, 2 and 3 are available as cognitive aids that can be made available for quick reference in the operating room.

Short Communication: Correlation of Thermographic Ocular and Auricular Temperatures with Rectal Temperature in Anesthetized Dogs

Objective

The aim of this study was to determine the correlation of both ocular and auricular thermographic temperatures with rectal temperatures and to determine the advantage of infrared thermography in clinical practice due to its ease of measurement. Animals. This study was designed as a pilot study and conducted on 6 mongrel male dogs during routine castration surgeries at the Kastamonu Municipality Temporary Animal Care Center.

Methods

Rectal temperatures and ocular-auricular thermographic images were taken from 6 dogs anesthetized (xylazine HCl 1 mg/kg and ketamine HCl 15 mg/kg) during routine neutering surgeries. Data were analyzed by Bland-Altman for correlation between rectal-ocular and rectal-auricular temperatures.

Results

Rectal temperatures were significantly higher than orbital and auricular temperatures. In the correlation test, no significant difference and correlation were found between the measurements.

Conclusion

As a result of the study, it was determined that the use of thermography was more advantageous than the waiting times of the digital thermometer used to record rectal temperatures. In addition, the noninvasive nature of thermography increased its acceptability in all dogs. The findings from this pilot study were considered to be at a level that could provide a basis for future studies.

Outpatient-Based High-Volume Liposuction: A Retrospective Review of 310 Consecutive Patients

BACKGROUND

Currently, the definition of large-volume liposuction is the removal of 5 L or more of total aspirate. Higher volumes of lipoaspirate come into consideration with higher BMIs, because more than 5 L is often required to achieve a satisfactory aesthetic result. The boundaries of what lipoaspirate volume is considered safe are based on historical opinion and are constantly in question.

OBJECTIVES

Because to date there have been no scientific data available to support a specific safe maximum volume of lipoaspirate, the authors discuss necessary conditions for safe high-volume lipoaspirate extraction.

METHODS

This retrospective study included 310 patients who had liposuction of ≥5 L over a 30-month period. All patients had 360° liposuction alone or in combination with other procedures.

RESULTS

Patient ages ranged from 20 to 66 with a mean age of 38.5 (SD = 9.3). Average operative time was 202 minutes (SD = 83.1). Mean total aspirate was 7.5 L (SD = 1.9). An average of 1.84 L (SD = 0.69) of intravenous fluids and 8.99 L (SD = 1.47) of tumescent fluid were administered. Urine output was maintained above 0.5 mL/kg/hr. There were no major cardiopulmonary complications or cases requiring blood transfusion.

CONCLUSIONS

High-volume liposuction is safe if proper preoperative, intraoperative, and postoperative protocols and techniques are employed. The authors believe that this bias should be modified and that sharing their experience with high-volume liposuction may help guide other surgeons to incorporate this practice with confidence and safety for better patient outcomes.

LEVEL OF EVIDENCE: 3

The Utility of Perioperative Products for the Prevention of Surgical Site Infections in Total Knee Arthroplasty and Lower Extremity Arthroplasty: A Systematic Review

Surgical site infections (SSIs) are among the most prevalent and devastating complications following lower extremity total joint arthroplasty (TJA). Strategies to reduce the rates can be divided into preoperative, perioperatives, and postoperative measures. A multicenter trial is underway to evaluate the efficacy of implementing a bundled care program for SSI prevention in lower extremity TJA including: (1) nasal decolonization; (2) surgical skin antisepsis; (3) antimicrobial incise draping; (4) temperature management; and (5) negative-pressure wound therapy for selected high-risk patients. The purposes of this systematic review were to provide a background and then to summarize the available evidence pertaining to each of these SSI-reduction strategies with special emphasis on total knee arthroplasty. A systematic review of the literature was conducted in accordance with the 2009 Preferred Reporting Items for Systematic Reviews and Meta-Analyses statement guidelines. Five individual literature searches were performed to identify studies evaluating nasal decolonization temperature management, surgical skin antisepsis, antimicrobial incise draping, and negative-pressure wound therapy. The highest level of evidence reports was used in each product review, and if there were insufficient arthroplasty papers on the particular topic, then papers were further culled from the surgical specialties to form the basis for the review. There was sufficient literature to assess all of the various prophylactic and preventative techniques. All five products used in the bundled program were supported for use as prophylactic agents or for the direct reduction of SSIs in both level I and II studies. This systematic review showed that various pre-, intra-, and postoperative strategies are efficacious in decreasing the risks of SSIs following lower extremity TJA procedures. Thus, including them in the armamentarium for SSI-reduction strategies for hip and knee arthroplasty surgeons should decrease the incidence of infections. We expect that the combined use of these products in an upcoming study will support these findings and may further enhance the reduction of total knee arthroplasty SSIs in a synergistic manner.

Resistant fabric warming is a viable alternative to forced-air warming to prevent inadvertent perioperative hypothermia during hemiarthroplasty in the elderly

BACKGROUND

Surgical site infection (SSI) is associated with inadvertent perioperative hypothermia (IPH). This can be prevented by active patient warming. However, results from comparisons of warming techniques are conflicting. They are based mostly on elective surgery, are from small numbers of patients, and are dominated by the market leader, forced-air warming (FAW). Furthermore, the definition of hypothermia is debatable and systematic reviews of warming systems conclude that a stricter control of temperature is required to study the benefits of warming.

AIM

To analyse core temperatures in detail in a large subset of elderly patients who took part in a randomized trial of patient warming following hemiarthroplasty who had received constant zero-flux thermometry to record their temperature.

METHODS

Regression models with a fixed effect for warming group and covariates related to temperature were compared for 257 participants randomized to FAW or resistant fabric warming (RFW) from a prior clinical trial.

FINDINGS

Those in the RFW group were -0.08°C cooler and had a cumulative hypothermia score -1.87 lower than those in the FAW group. There was no difference in the proportion of hypothermic patients at either <36.5°C or <36.0°C.

CONCLUSIONS

This is the first study to provide accurate temperature measurements in patients undergoing a procedure predominantly under regional rather than general anaesthetic. It shows that RFW is a viable alternative to FAW for preventing IPH during hemiarthroplasty. Further studies are needed to measure the benefits of patient warming in terms of clinically important outcomes.

Changes in tracheal, oesophageal and rectal temperature over 60 minutes anaesthesia in non-heated dogs, spontaneously breathing or mechanically ventilated

The objective of this prospective randomised clinical study was to determine the differences in the tracheal, oesophageal and rectal temperature in spontaneously breathing or mechanically ventilated dogs. A total of thirty dogs were allocated to the SPO-group breathing spontaneously (n = 15) or the MEC-group ventilated mechanically (n = 15). Anaesthesia was established using a medetomidine-butorphanol-propofol-isoflurane combination. The tracheal (T-Tra), oesophageal (T-Oes), rectal (T-Rec), inspired gas (T-Gas), room (T-Room) temperatures, respiratory frequency (f R), heart rate (HR), mean arterial pressure (MAP) and end-tidal carbon dioxide concentration (ETCO2) were measured after connecting to a re-breathing system (baseline) and subsequently in 10-minute intervals for 60 minutes. The data were analysed using ANOVA and Steel-Dwass tests (P < 0.05). In the SPO-group, the T-Tra, was significantly lower at T30, T40, T50, T60, the T-Oes and T-Rec at T40, T50, T60, compared to the baseline. In the MEC-group, the T-Tra and T-Oes was significantly lower at T30, T40, T50, T60, the T-Rec at T40, T50, T60, compared to the baseline. In the SPO-group, the f R was significantly lower for all the times and the ETCO2 higher at T10, T20, T30, T40, T50 compared to the MEC-group. No other differences were detected. During anaesthesia, there is a comparable decrease in body temperatures, regardless of whether the dogs are breathing spontaneously or ventilated mechanically.

Forced-Air Convection Versus Underbody Conduction Warming Strategies to Maintain Perioperative Normothermia in Patients Undergoing Total Joint Arthroplasty

Background

Forced-air warming is an established strategy for maintaining perioperative normothermia. However, this warming strategy can potentially contaminate the surgical field by circulating nonsterile air. This study aimed to determine whether changing practice away from this method resulted in non-inferior rates of perioperative hypothermia.

Methods

We performed a chart review of primary total hip and knee arthroplasty patients from 2014 to 2017, when the strategy of intraoperative forced-air warming (FAW) was changed to preoperative FAW along with intraoperative underbody conduction warming (CW) with an underbody warming mattress. Data included patient temperatures throughout all phases of care, blood loss and transfusion requirements, length of postanesthesia care unit (PACU) and hospital stays, and 30-day infection and mortality.

Results

A total of 769 charts were reviewed; 349 patients underwent surgery before the practice change and 420 after. Mean (SD; 95% CI) body temperatures at the time of incision were lower for group 1 than for group 2 (34.55 vs 35.52 °C [0.97 °C; 95% CI, 0.72-1.23 °C]). The average nadir of intraoperative body temperature was lower for group 1 than for group 2 (difference of means, 0.44 °C; 95% CI, 0.18-0.71 °C). Group 2 had a higher percentage of patients who presented hypothermic (temperature <36.0 °C) on arrival in the PACU (12.9% vs 7.7%).

Conclusion

Preoperative convective warming combined with intraoperative underbody conductive warming maintains normothermia during primary total joint arthroplasty and is non-inferior to forced-air intraoperative warming alone.

The Impact of Intraoperative Hypothermia on Blood Loss and Allogenic Blood Transfusion in Total Knee and Hip Arthroplasty: A Retrospective Study

Background

Total joint arthroplasty (TJA) usually leads to substantial blood loss, which may cause allogenic blood transfusion. Hypothermia occurring during operation has been reported to increase blood loss and transfusion rates in nonorthopedic cohorts. However, the relationship between intraoperative hypothermia and blood loss remains controversial in patients undergoing orthopedic surgeries. The aims of this study were to investigate the incidence of hypothermia and identify the impact of intraoperative body temperature and hypothermia on blood loss and transfusion rates in total knee and hip arthroplasty (TKA and THA, respectively).

Methods

This retrospective study enrolled 616 consecutive patients, who underwent primary unilateral TKA or THA at our institution during the period from April 2012 to July 2014. The occurrence of a temperature below 36°C during the operation was documented to identify the incidence of hypothermia. Univariate analysis was performed to find the risk factors for hypothermia. Multiple regression analysis and multivariate logistic regression analysis were employed to explore the association of intraoperative temperature and hypothermia with intraoperative blood loss and perioperative blood transfusion.

Results

The incidence of intraoperative hypothermia was 13.5%, 14.0%, and 13.1% in TJA, TKA, and THA, respectively. Intraoperative temperature (P = 0.045, P = 0.006) and hypothermia (P = 0.042, P < 0.001) were associated with intraoperative blood loss and perioperative transfusion in TKA. Intraoperative temperature (P = 0.002) was negatively related to the amount of blood loss, and hypothermia (P = 0.031) was the independent risk factor for transfusion in THA.

Conclusion

Intraoperative hypothermia is associated with increased blood loss and transfusion rates in TJA. Efforts should be made to maintain normothermia during operation in these patients.

Comparing Forced-Air to Resistive-Polymer Warming for Perioperative Temperature Management: A Retrospective Study

PURPOSE

Compare perioperative temperature management between forced-air warming (FAW) and resistive-polymer heating blankets (RHBs).

DESIGN

A retrospective, quasi-experimental study.

METHODS

Retrospective data analysis of nonspine orthopedic cases (N = 426) over a one-year period including FAW (n = 119) and RHBs (n = 307).

FINDINGS

FAW was associated with a significantly higher final intraoperative temperature (P = .001, d = 0.46) than the RHB. The incidence of hypothermia was not found to be significantly different at the end (P = .102) or anytime throughout surgery (P = .270). Of all patients who started hypothermic, the FAW group had a lower incidence of hypothermia at the end of surgery (P = .023).

CONCLUSIONS

FAW was associated with higher final temperatures and a greater number of normothermic patients than RHBs. However, no causal relationship between a warming device and hypothermia incidence should be assumed.

The effectiveness of air-free warming systems on perioperative hypothermia in total hip and knee arthroplasty: A systematic review and meta-analysis

BACKGROUND

Perioperative hypothermia is a common and serious complication during surgery. Different warming systems are used to prevent perioperative hypothermia. However, there have been no previous meta-analyses of the effectiveness of air-free warming systems on perioperative hypothermia in patients undergoing joint arthroplasty.

METHODS

We systematically searched PubMed, EMBASE, Cochrane Library, and China National Knowledge Infrastructure (CNKI) databases to collect randomized controlled trials (RCTs) from inception to August 2018. These RCTs compared the effects of air-free warming with forced-air (FA) warming system in patients undergoing joint arthroplasty. Postoperative temperature, core temperature during surgery, thermal comfort, blood loss and incidence of shivering and hypothermia were analyzed.

RESULTS

A total of 287 patients from 6 clinical studies were included in the analysis. In summary, there was no significant difference in the postoperative temperature (WMD -0.043, 95% CI -0.32 to 0.23, P = .758) between the air-free warming and FA warming groups. No statistical difference (WMD 0.058, 95% CI -0.10 to 0.22, P = .475) was found in core temperatures at 0 minutes during surgery between the air-free warming and FA warming groups. Furthermore, there was no statistical difference in thermal comfort, blood loss or incidence of shivering and hypothermia between the air-free warming and FA warming groups.

CONCLUSIONS

Air-free warming system was as effective as FA warming system in patients undergoing joint arthroplasty.

Forced-Air Warming and Resistive Heating Devices. Updated Perspectives on Safety and Surgical Site Infections

Introduction: Perioperative hypothermia is one of the most common phenomena seen among surgical patients, leading to numerous adverse outcomes such as intraoperative blood loss, cardiac events, coagulopathy, increased hospital stay and associated costs. Forced air warming (FAW) and resistive heating (RH) are the two most commonly used and widely studied devices to prevent perioperative hypothermia. The effect of FAW on operating room laminar flow and surgical site infection is unclear and we initiated an extensive literature search in order to get a scientific insight of this aspect.

Material and Methods: The literature search was conducted using the Medline search engine, PubMed, Cochrane review, google scholar, and OSU library.

Results: Out of 92 Articles considered initially for review we selected a total of 73 relevant references. Currently there is no robust evidence to support that FAW can increase SSIs. In addition, both of the two warming devices present safety problems.

Conclusion: As unbiased independent reviewers, we advise clinicians to weigh the risks and benefits when using either one of these devices; no change in the current practice is necessary until further data emerges.

Normothermia in Arthroplasty

BACKGROUND

Since the initial design of surgical theatres, the thermal environment of the operating suite itself has been an area of concern and robust discussion. In the 1950s, correspondence in the British Medical Journal discussed the most suitable design for a surgeon's cap to prevent sweat from dripping onto the surgical field. These deliberations stimulated questions about the effects of sweat-provoking environments on the efficiency of the surgical team, not to mention the effects on the patient. Although these benefits translate to implant-based orthopedic surgery, they remain poorly understood and, at times, ignored.

METHODS

A review and synthesis of the body of literature on the topic of maintenance of normothermia was performed.

RESULTS

Maintenance of normothermia in orthopedic surgery has been proven to have broad implications from bench top to bedside. Normothermia has been shown to impact everything from nitrogen loss and catabolism after hip fracture surgery to infection rates after elective arthroplasty.

CONCLUSION

Given both the physiologic impact this has on patients, as well as a change in the medicolegal environment around this topic, a general understanding of these concepts should be invaluable to all surgeons.

Safety and efficacy of resistive polymer versus forced air warming in total joint surgery

Background

Forced-air warming is used as a mechanism to prevent hypothermia and adverse outcomes associated with hypothermia among patients undergoing surgery. Patient safety in healthcare includes the use of devices and technology that minimize potential adverse events to patients. The present study sought to compare the capabilities of patient warming between two different devices that use different mechanisms of warming: forced-air warming and non-air warming.

Methods

One hundred twenty patients undergoing total hip or total knee arthroplasty received patient warming via a forced warming device or non-air warming fabric conductive material. The project was part of a quality improvement initiative to identify warming devices effective in maintaining normothermic patient core temperatures during orthopedic surgery.

Results

Forced-air warming and non-air warming achieved similar results in maintaining the core temperature of patients undergoing total knee or hip arthroplasty. No adverse events were reported in either group. Operating room staff observed that the non-air warming device was less noisy and appreciated the disposable covers that could be changed after each surgical case.

Conclusions

These findings demonstrate that hypothermia is achieved by both forced-air and non-forced air warming devices among total knee and hip arthroplasty patients. The potential for airflow disruption is present with the forced-air warming device and does not exist with the non-forced air device. The disruption of laminar airflow may be associated with surgical site infections. The disposable covers used to protect the device and patient have potential implications for surgical site infection. Quality improvement efforts aimed to enhance patient safety should include the implementation of healthcare equipment with the least known or suspected risk.

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.

Comparison of resistive heating and forced-air warming to prevent inadvertent perioperative hypothermia

BACKGROUND

Forced-air warming is a commonly used warming modality, which has been shown to reduce the incidence of inadvertent perioperative hypothermia (<36°C). The reusable resistive heating mattresses offer a potentially cheaper alternative, however, and one of the research recommendations from the National Institute for Health and Care Excellence was to evaluate such devices formally. We conducted a randomized single-blinded study comparing perioperative hypothermia in patients receiving resistive heating or forced-air warming.

METHODS

A total of 160 patients undergoing non-emergency surgery were recruited and randomly allocated to receive either forced-air warming (n=78) or resistive heating (n=82) in the perioperative period. Patient core temperatures were monitored after induction of anaesthesia until the end of surgery and in the recovery room. Our primary outcome measures included the final intraoperative temperature and incidence of hypothermia at the end of surgery.

RESULTS

There was a significantly higher rate of hypothermia at the end of surgery in the resistive heating group compared with the forced-air warming group (P=0.017). Final intraoperative temperatures were also significantly lower in the resistive heating group (35.9 compared with 36.1°C, P=0.029). Hypothermia at the end of surgery in both warming groups was common (36% forced air warming, 54% resistive heating).

CONCLUSION

Our results suggest that forced-air warming is more effective than resistive heating in preventing postoperative hypothermia.

CLINICAL TRIAL REGISTRATION

NCT01056991.

Meta-analysis: effectiveness of forced-air warming for prevention of perioperative hypothermia in surgical patients

AIM

The aim of this study was to evaluate the effectiveness of forced-air warming for preventing perioperative hypothermia.

BACKGROUND

Perioperative hypothermia commonly occurs in patients receiving anaesthesia during surgeries. However, the effectiveness of warming systems requires verification.

DESIGN

Systematic review incorporating meta-analysis.

DATA SOURCES

We searched OVID, PubMed, Cochrane Library, Medline, CINAHL, CETD and CEPS databases (2001-2015) for randomized controlled trials published in English and Chinese. Outcome measures of interests were body temperature and thermal comfort.

REVIEW METHODS

Cochrane methods, Quality of evidence (GRADE) assessments and Jadad Quality Score were used.

RESULTS

Twenty-nine trials (1875 patients) met inclusion criteria, including seven trials (502 patients) related to thermal comfort. Results showed that: (1) forced-air warming was more effective than passive insulation and circulating-water mattresses; (2) there was no statistically significant difference among forced-air warming, resistive heating blankets, radiant warming systems and circulating-water garments; and (3) that thermal comfort provided by forced-air warming was superior to that of passive insulation, resistive heating blankets and radiant warming systems, but inferior to that of circulating-water mattresses.

CONCLUSIONS

Forced-air warming prevents perioperative hypothermia more effectively than passive insulation and circulating-water mattresses, whereas there is no statistically significant difference in its effectiveness compared with circulating-water garments, resistive heating blankets and radiant warming systems.

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.

Infection control hazards associated with the use of forced-air warming in operating theatres

A review is presented of the published experimental and clinical research into the infection control hazards of using forced air-warming (FAW) in operating theatres to prevent inadvertent hypothermia. This evidence has been reviewed with emphasis on the use of ultra-clean ventilation, any interaction it has with different types of patient warming (and FAW in particular), and any related increased risk of surgical site infection (SSI). We conclude that FAW does contaminate ultra-clean air ventilation; however, there appears to be no definite link to an increased risk of SSI based on current research. Nevertheless, whereas this remains unproven, we recommend that surgeons should at least consider alternative patient-warming systems in areas where contamination of the operative field may be critical. Although this is not a systematic review of acceptable randomized controlled clinical trials, which do not exist, it does identify that there is a need for definitive research in this field.

Unintentional perioperative hypothermia is associated with severe complications and high mortality in elective operations

INTRODUCTION

Hypothermia occurs in as many as 7% of elective colorectal operations and is an underestimated risk factor for complications and death. Rewarming of hypothermic patients alone is not sufficient to prevent such adverse events. We investigated the outcomes of patients who became hypothermic (<35°C) after elective operations and compared them with closely matched, nonhypothermic operative patients to better define the impact of hypothermia on surgical outcomes, as well as to identify independent risk factors for hypothermia.

METHODS

We queried the University HealthSystem Consortium (UHC) database for elective operative patients who became unintentionally hypothermic from October 2008 to March 2012, and identified 707 patients. Exclusion criteria were deliberate hypothermia, age <18 years, or death on day of admission. Separately, to validate the accuracy of hypothermia coding, we reviewed the hospital charts of all University of Louisville Hospital patients with hypothermia whose data were submitted to UHC.

RESULTS

All patients from UHC with a code for hypothermia were indeed unintentionally hypothermic. Hypothermic patients undergoing elective operations experienced a 4-fold increase in mortality (17.0% vs 4.0%; P < .001) and a doubled complication rate (26.3% vs 13.9%; P < .001), in which sepsis and stroke increased the most. Several independent risk factors for hypothermia were amenable to preoperative improvement: anemia, chronic renal impairment, and unintended weight loss. Severity of illness on admission, age >65 years, male sex, and neurologic disorders also were risk factors.

CONCLUSION

Hypothermia is associated with an increased rate of mortality and complications. Preventive treatment of these risk factors before operation and aggressive warming measures in the "at risk" population may decrease hypothermia-related morbidity and mortality in elective operations. Randomized-controlled trials should be conducted to evaluate the impact of aggressive warming measures in the at-risk population.

Comparison of the efficacy of a forced-air warming system and circulating-water mattress on core temperature and post-anesthesia shivering in elderly patients undergoing total knee arthroplasty under spinal anesthesia

Background

In the present study, we compared changes in body temperature and the occurrence of shivering in elderly patients undergoing total knee arthroplasty under spinal anesthesia during warming with either a forced-air warming system or a circulating-water mattress.

Methods

Forty-six patients were randomly assigned to either the forced-air warming system (N = 23) or circulating-water mattress (N = 23) group. Core temperature was recorded using measurements at the tympanic membrane and rectum. In addition, the incidence and intensity of post-anesthesia shivering and verbal analogue score for thermal comfort were simultaneously assessed.

Results

Core temperature outcomes did not differ between the groups. The incidence (13.0 vs 43.5%, P < 0.05) and intensity (20/2/1/0/0 vs 13/5/3/2/0, P < 0.05) of post-anesthesia shivering was significantly lower in the forced-air system group than in the circulating-water mattress group.

Conclusions

The circulating-water mattress was as effective as the forced-air warming system for maintaining body temperature. However, the forced-air warming system was superior to the circulating-water mattress in reducing the incidence of post-anesthesia shivering.

Peri-operative warming devices: performance and clinical application

Since the adverse consequences of accidental peri-operative hypothermia have been recognised, there has been a rapid expansion in the development of new warming equipment designed to prevent it. This is a review of peri-operative warming devices and a critique of the evidence assessing their performance. Forced-air warming is a common and extensively tested warming modality that outperforms passive insulation and water mattresses, and is at least as effective as resistive heating. More recently developed devices include circulating water garments, which have shown promising results due to their ability to cover large surface areas, and negative pressure devices aimed at improving subcutaneous perfusion for warming. We also discuss the challenge of fluid warming, looking particularly at how devices' performance varies according to flow rate. Our ultimate aim is to provide a guide through the bewildering array of devices on the market so that clinicians can make informed and accurate choices for their particular hospital environment.

Hypothermia Prevention During Surgery: Comparison Between Thermal Mattress And Thermal Blanket


This study aimed to compare the efficiency of the thermal blanket and thermal mattress in the prevention of hypothermia during surgery. Thirty-eight randomized patients were divided into two groups (G1 – thermal blanket and G2 - thermal mattress). The variables studied were: length of surgery, length of stay in the post-anesthetic care unit, period without using the device after thermal induction, transport time from the operating room to post-anesthetic care unit, intraoperative fluid infusion, surgery size, anesthetic technique, age, body mass index, esophageal, axillary and operating room temperature. In G2, length of surgery and starch infusion longer was higher (both p=0.03), but no hypothermia occurred. During the surgical anesthetic procedure, the axillary temperature was higher at 120 minutes (p=0.04), and esophageal temperature was higher at 120 (p=0.002) and 180 minutes (p=0.03) and at the end of the procedure (p=0.002). The thermal mattress was more effective in preventing hypothermia during surgery.

Active cutaneous warming systems to prevent intraoperative hypothermia: a systematic review

This study analyzed the evidence available in the literature concerning the effectiveness of different active cutaneous warming systems to prevent intraoperative hypothermia. This is a systematic review with primary studies found in the following databases: CINAHL, EMBASE, Cochrane Register of Controlled Trials and Medline. The sample comprised 23 randomized controlled trials. There is evidence in the literature indicating that the circulating water garment system is the most effective in maintaining patient body temperature. These results can support nurses in the decision-making process concerning the implementation of effective measures to maintain normothermia, though the decision of health services concerning which system to choose should also take into account its cost-benefit status given the cost related to the acquisition of such systems.

Maintenance of core body temperature in anaesthetised pigeons (Columba livia domestica): a comparison of two thermal devices

Active thermal devices are used to prevent hypothermia during anaesthetic procedures. Two thermal devices, one conductive and one convective, were compared for their effect on maintenance of core body temperature (CBT) during 1h of general anaesthesia in pigeons (Columba livia domestica). In a randomised crossover trial, CBT decreased significantly less with the conductive device than when the convective device was used (2.5 ± 0.7°C and 3.8 ± 0.9°C, respectively; P<0.01). Moreover, CBT was maintained above a clinically acceptable level of 38.3°C in 82% of pigeons when the conductive device was selected, compared to 14% of pigeons with the convective device. The use of the conductive device is therefore recommended in preference to the convective device when performing anaesthetic procedures in birds.