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

BACKGROUND

Hypothermia is a common perioperative problem that can lead to severe complications. We evaluated whether a heated mattress (HM) is superior to a warm air blanket (WA) in preventing perioperative hypothermia in patients undergoing total hip arthroplasty (THA) or total knee arthroplasty (TKA).

METHODS

A retrospective cohort study was performed in a teaching hospital and data were collected for all patients undergoing THA or TKA between January 1, 2015 and May 1, 2022. We used logistic and linear regressions to analyze hypothermia occurrence and important complications. Results were adjusted for confounders and time, and was present in all subgroups and after imputation of missing data.

RESULTS

In total, 4,683 of 5,497 patients had information on type of heating. We found more perioperative hypothermia in patients treated with an HM compared to a WA for both THA (odds ratio-adjusted 1.42 [1.0 to 1.6] P = .06) and TKA (odds ratio-adjusted 2.10 [1.5 to 3.0] P < .01). There was no difference in postoperative infections between groups (all between 0.5% and 1.3%). Patients who had an HM significantly stayed longer in the postoperative ward (a mean difference of 4 [TKA] to 6 [THA] minutes, P < .01), but there was no difference in hospital stay.

CONCLUSION

A WA is superior compared to an HM in preventing perioperative hypothermia, with no increased risk of complications. Patients who have an HM stayed longer at the postoperative ward, potentially because of higher hypothermia rates. Therefore, it is suggested to use a WA instead of an HM.

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

Comparative effects of warming systems applied to different parts of the body on hypothermia in adults undergoing abdominal surgery: A systematic review and network meta-analysis of randomized controlled trials

STUDY OBJECTIVE

The prevention of perioperative hypothermia after anesthesia induction is a critical concern in patients undergoing abdominal surgery. The effectiveness of various warming systems for preventing hypothermia and shivering when applied to specific areas of the body remains undetermined.

DESIGN

Systematic review and network meta-analysis.

SETTING

Operating room.

INTERVENTION

Five electronic databases were searched, including only randomized control trials (RCTs) reporting the effects of warming systems applied to specific body sites on the intraoperative core temperature and postoperative risk of shivering in adults undergoing abdominal surgery. A multivariate random-effects network meta-analysis with a frequentist framework was implemented for data analysis.

MEASUREMENTS

The primary outcome was the core body temperature 60 and 120 min after anesthesia induction for abdominal surgery. The secondary outcome was the incidence of postoperative shivering.

RESULTS

This review comprised a total of 24 RCTs including 1119 patients. At 60 and 120 min after anesthesia induction, a forced-air warming system applied to the upper body (0.3 °C and 95% confidence intervals = [0.3 to 0.4], 1.0 °C [0.7 to 1.3]), lower body (0.4 °C [0.3 to 0.5], 0.9 °C [0.5 to 1.2]), and underbody (0.5 °C [0.5 to 0.6], 1.2 °C [0.9 to 1.6]) was superior to passive insulation in terms of core body temperature regulation. Compared with passive insulation, the forced-air warming system applied to the lower body (odds ratio = 0.06) or underbody (0.44) and the electric heating blanket to the lower body (0.02) or the whole body (0.07) significantly reduced the risk of shivering.

CONCLUSIONS

The results of this NMA revealed that forced-air warming with an underbody blanket effectively elevates core body temperatures in 60 and 120 min after induction of anesthesia and prevents shivering in patients recovering from abdominal surgery.

The Impact of Ambient Temperature Control Across Various Care Settings on Outcomes in Burn Patients: A Review Article

Ambient/room temperature settings in burn treatment areas vary greatly due to a lack of evidence-based guidelines to direct care. While it is generally understood that ambient/room temperature impacts patient body temperature and metabolism, the ideal settings for optimizing patient outcomes are unclear. The literature assessing this topic is scarce, with many of the articles having significant limitations. We aim to summarize the current evidence for ambient/room temperature control, to address gaps in current reviews addressing this topic, and to elucidate topics requiring further research. PubMed and Google Scholar databases were queried for studies which evaluated the effect of the ambient/room temperature on burn patient core body temperature, patient metabolism, and outcomes among those treated in trauma bays, burn ICUs, and operating rooms. Although existing literature lacks sufficient patient outcome data regarding specific ambient/room temperatures, we highlight physiological processes that are impacted by changes in room temperatures in an effort to describe strategies that can allow for improved patient core body temperature control and outcomes in burn care settings.

Potential sources of operating room air contamination: a preliminary study

BACKGROUND

The Neptune® surgical suction system (NSSS) and the Bair Hugger® (BH) forced-air warmer both discharge filtered exhaust or heated air into the operating room (OR), often in close proximity to a surgical site.

AIM

To assess the effectiveness of this filtration, we examined the quantity and identity of microbial colonies emitted from their output ports compared with those obtained from circulating air entering the OR.

METHODS

Air samples were collected from each device using industry-standard sampling devices in which a measured volume of air is impacted on to a blood agar plate at a controlled flow rate. Twelve ORs were studied. Sample plates were incubated for one week per study protocol, then interpreted for colony counts and sent for species identification.

FINDINGS

The average colony count from the NSSS exhaust was not significantly different from that obtained from room air samples, however the average count from the BH output was significantly higher (P=0.0086) than room air. Genetic identification profiles revealed the presence of environmental or commensal organisms that differed depending on the source. High variability in colony counts from both devices suggests that certain NSSS and BH devices could be significant sources of OR air contamination.

CONCLUSIONS

Our study showed that the BH patient warming device could be a source of airborne microbial contamination in the OR and that individual BH and NSSS units exhibit a higher output of microbial cfu than would be expected compared with incoming room air. We make simple suggestions on ways to mitigate these risks.

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

Prevention of Perioperative Hypothermia: A Prospective, Randomized, Controlled Trial of Bair Hugger Versus Inditherm in Patients Undergoing Elective Arthroscopic Shoulder Surgery

PURPOSE

To determine if a clinically significant difference in the core body temperature (CBT) exists between the Bair Hugger (BH) and Inditherm (IT) warming devices in patients undergoing arthroscopic shoulder surgery.

METHODS

This was a parallel, 2-treatment, prospective, randomized, controlled trial conducted in patients undergoing elective arthroscopic shoulder surgery in the beach-chair position using room-temperature irrigation fluid. The BH was used as the indicative forced-air warming device, whereas the IT served as the indicative resistive heating system. By use of a minimal clinically significant difference of 0.6°C and standard deviation of 0.6°C, a power analysis showed that a sample size of 90 patients (45 per group) would be required. Patients fulfilling the inclusion criteria were recruited from the clinics of the senior authors. Anesthetic and surgical protocols were standardized. The intraoperative CBT was recorded every 5 minutes using a nasopharyngeal thermistor probe. Demographic data as well as the volume of irrigation fluid used were also noted.

RESULTS

A steady decline in the CBT was observed in both groups up to 30 minutes after induction of anesthesia. Beyond 30 minutes, the BH group showed a gradual increase in temperature whereas it continued to decline in the IT group. A statistically significant difference in the CBT was observed from 60 minutes onward (P = .025). This difference continued to increase up to 90 minutes (P < .001). At no time was a rise in the CBT observed in the IT group. At completion of the study and surgical procedure, 13 of 47 patients in the BH group and 32 of 44 patients in the IT group had hypothermia (P = .0002).

CONCLUSIONS

The CBT was statistically significantly better with the use of the BH compared with the IT mattress. However, the differences in the CBT did not reach the level of clinical significance of 0.6°C. Far fewer patients in the BH group had hypothermia at the end of surgery. Therefore, this study supports the use of the BH in elective arthroscopic shoulder surgery for the prevention of hypothermia.

LEVEL OF EVIDENCE

Level I.

Editorial Commentary: Just Getting Warmed Up: Risks, Benefits, and Economics of Active Warming Devices

Efforts to maintain normothermia should be a part of every patient's perioperative care. Risks, benefits, and economic implications should be considered when deciding how to use active warming devices for orthopaedic surgery. The Centers for Medicare & Medicaid Services has implemented economic incentives and penalties driving hospitals to invest in active warming devices, including forced-air warmers and resistive heating devices. Even though forced-air warmers and resistive heating blankets are likely to statistically improve patient temperatures, they may not be worth the additional cost for shorter, less invasive, elective arthroscopic surgeries. In addition, recent research demonstrates minimal clinically significant differences between these 2 types of devices. Concern regarding possible increased risk of surgical-site contamination with forced-air warmers warrants further study but, again, is unlikely clinically relevant to arthroscopic cases, and proper staff training and warming equipment routine maintenance could minimize patient risk.

Reducing Implant Infection in Orthopaedics (RIIiO): Results of a pilot study comparing the influence of forced air and resistive fabric warming technologies on postoperative infections following orthopaedic implant surgery

BACKGROUND

Active warming during surgery prevents perioperative hypothermia but the effectiveness and postoperative infection rates may differ between warming technologies.

AIM

To establish the recruitment and data management strategies needed for a full trial comparing postoperative infection rates associated with forced air warming (FAW) versus resistive fabric warming (RFW) in patients aged >65 years undergoing hemiarthroplasty following fractured neck of femur.

METHODS

Participants were randomized 1:1 in permuted blocks to FAW or RFW. Hypothermia was defined as a temperature of <36°C at the end of surgery. Primary outcomes were the number of participants recruited and the number with definitive deep surgical site infections.

FINDINGS

A total of 515 participants were randomized at six sites over a period of 18 months. Follow-up was completed for 70.1%. Thirty-seven participants were hypothermic (7.5% in the FAW group; 9.7% in the RFW group). The mean temperatures before anaesthesia and at the end of surgery were similar. For the primary clinical outcome, there were four deep surgical site infections in the FAW group and three in the RFW group. All participants who developed a postoperative infection had antibiotic prophylaxis, a cemented prosthesis, and were operated under laminar airflow; none was hypothermic. There were no serious adverse events related to warming.

CONCLUSION

Surgical site infections were identified in both groups. Progression from the pilot to the full trial is possible but will need to take account of the high attrition rate.

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 System: Evaluation of Internal System Contamination

BACKGROUND

Despite the indisputable need to prevent peri-operative hypothermia, some evidence in the literature questions the possible role of forced air warming systems as a risk factor for the occurrence of surgical site infection. The objective of the study is to evaluate the micro-biologic safety of a forced air warming systems (FAW) in relation to the risk of emission of micro-organisms in the surgical environment.

METHODS

A quantitative, descriptive-exploratory laboratory study performed in a large hospital. An evaluation of possible internal contamination was performed by collecting air from the hose onto plates containing Trypticase Soy Agar. The experiment was performed in triplicate two months after replacing the filter and again after six months using a random sample of 50% of the FAW in use, which corresponded to 13 FAW and a total of 75 samples.

RESULTS

Among the 39 samples analyzed in the first stage, only nine (23.1%) plates presented microbial growth of one or two colonies, while only six (16.7%) plates of the 36 evaluated samples in the second phase had growth of one or two colonies.

CONCLUSIONS

This study showed small microbial growth of culture after 48 hours after filter replacement. New investigations that correlate the findings of micro-biology analysis and the occurrence of surgical site infection should be conducted.

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.

High Efficiency Particulate Air Filters Do Not Affect Acute Infection Rates During Primary Total Joint Arthroplasty Using Forced Air Warmers

BACKGROUND

Studies have suggested that forced-air warmers (FAWs) increase contamination of the surgical site. In response, FAWs with high efficiency particulate air filters (FAW-HEPA) were introduced. This study compared infection rates following primary total joint arthroplasty (TJA) using FAW and FAW-HEPA.

METHODS

Primary TJA patients at a single healthcare system were retrospectively reviewed. A total of 5405 THA (n = 2419) and TKA (n = 2986) consecutive cases in 2013 and 2015 were identified. Patients in 2013 (n = 2792) had procedures using FAW, while FAW-HEPA was used in 2015 (n = 2613). The primary outcome was overall infection rate within 90-days. Sub-categorization of infections as periprosthetic joint infection (PJI) or surgical site infection (SSI) was also conducted. PJI was defined as reoperation with arthrotomy or meeting Musculoskeletal Infection Society (MSIS) criteria. SSI was defined as wound complications requiring antibiotics or irrigation/debridement.

RESULTS

The FAW and FAW-HEPA groups had similar rates of overall infection (1.65% [n = 46] vs 1.61% [n = 42], P > .99), SSI (1.18% [n = 33] vs 0.84% [n = 22], P = .27), and PJI (0.47% [n = 13] vs 0.77% [n = 20], P = .22). Regression models did not show FAW to be an independent risk factor for increased overall infection (odds ratio [OR] 1.00, 95% confidence interval [CI] 0.65-1.57, P = .97), SSI (OR 1.47, 95% CI 0.83-2.58, P = .18), or PJI (OR 0.53, 95% CI 0.25-1.13, P = .09).

CONCLUSION

FAW were not correlated with a higher risk of overall infection, SSI, or PJI during TJA when compared to FAW-HEPA devices.

Effect of heated-air blanket on the dispersion of squames in an operating room

High-fidelity, predictive fluid flow simulations of the interactions between the rising thermal plumes from forced air warming blower and the ultra-clean ventilation air in an operating room (OR) are conducted to explore whether this complex flow can impact the dispersion of squames to the surgical site. A large-eddy simulation, accurately capturing the spatiotemporal evolution of the flow in 3 dimensions together with the trajectories of squames, is performed for a realistic OR consisting of an operating table (OT), side tables, surgical lamps, medical staff, and a patient. Two cases are studied with blower-off and blower-on together with Lagrangian trajectories of 3 million squames initially placed on the floor surrounding the OT. The large-eddy simulation results show that with the blower-off, squames are quickly transported by the ventilation air away from the table and towards the exit grilles. In contrast, with the hot air blower turned on, the ventilation airflow above and below the OT is disrupted significantly. The rising thermal plumes from the hot air blower drag the squames above the OT and the side tables and then they are advected downwards toward the surgical site by the ventilation air from the ceiling. Temporal history of the number of squames reaching 4 imaginary boxes surrounding the side tables, the OT, and the patient's knee shows that several particles reach these boxes for the blower-on case.

Effects of Forced Air Warming on Airflow around the Operating Table

BACKGROUND

Forced air warming systems are used to maintain body temperature during surgery. Benefits of forced air warming have been established, but the possibility that it may disturb the operating room environment and contribute to surgical site contamination is debated. The direction and speed of forced air warming airflow and the influence of laminar airflow in the operating room have not been reported.

METHODS

In one institutional operating room, we examined changes in airflow speed and direction from a lower-body forced air warming device with sterile drapes mimicking abdominal surgery or total knee arthroplasty, and effects of laminar airflow, using a three-dimensional ultrasonic anemometer. Airflow from forced air warming and effects of laminar airflow were visualized using special smoke and laser light.

RESULTS

Forced air warming caused upward airflow (39 cm/s) in the patient head area and a unidirectional convection flow (9 to 14 cm/s) along the ceiling from head to foot. No convection flows were observed around the sides of the operating table. Downward laminar airflow of approximately 40 cm/s counteracted the upward airflow caused by forced air warming and formed downward airflow at 36 to 45 cm/s. Downward airflows (34 to 56 cm/s) flowing diagonally away from the operating table were detected at operating table height in both sides.

CONCLUSIONS

Airflow caused by forced air warming is well counteracted by downward laminar airflow from the ceiling. Thus it would be less likely to cause surgical field contamination in the presence of sufficient laminar airflow.

Temperature management under general anesthesia: Compulsion or option

Administration of general anesthesia requires continuous monitoring of vital parameters of the body including body temperature. However, temperature continues to be one of the least seriously monitored parameters perioperatively. Inadvertent perioperative hypothermia is a relatively common occurrence with both general and regional anesthesia and can have significant adverse impact on patients' outcome. While guidelines for perioperative temperature management have been proposed, there are no specific guidelines regarding the best site or best modality of temperature monitoring and management intraoperatively. Various warming and cooling devices are available which help maintain perioperative normothermia. This article discusses the physiology of thermoregulation, effects of anesthesia on thermoregulation, various temperature monitoring sites and methods, perioperative warming devices, guidelines for perioperative temperature management and inadvertent temperature complications (hypothermia/hyperthermia) and measures to control it in the operating room.

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.

Forced-Air Warming Discontinued: Periprosthetic Joint Infection Rates Drop

Several studies have shown that the waste heat from forced-air warming (FAW) escapes near the floor and warms the contaminated air resident near the floor. The waste heat then forms into convection currents that rise up and contaminate the sterile field above the surgical table. It has been shown that a single airborne bacterium can cause a periprosthetic joint infection (PJI) following joint replacement surgery. We retrospectively compared PJI rates during a period of FAW to a period of air-free conductive fabric electric warming (CFW) at three hospitals. Surgical and antibiotic protocols were held constant. The pooled multicenter data showed a decreased PJI rate of 78% following the discontinuation of FAW and a switch to air-free CFW (n=2034; P=0.002). The 78% reduction in joint implant infections observed when FAW was discontinued suggests that there is a link between the waste FAW heat and PJIs.

Airborne bacterial contamination during orthopedic surgery: A randomized controlled pilot trial

STUDY OBJECTIVE

Several factors such as lack of unidirectional, turbulent free laminar airflow, duration of surgery, patient warming system, or the number of health professionals in the OR have been shown or suspected to increase the number of airborne bacteria. The objective of this study was to perform a multivariate analysis of bacterial counts in the OR in patients during minor orthopedic surgery.

DESIGN

Prospective, randomized pilot study.

SETTING

Medical University of Vienna, Austria.

PATIENTS

Eighty patients undergoing minor orthopedic surgery were included in the study.

INTERVENTIONS

Surgery took place in ORs with and without a unidirectional turbulent free laminar airflow system, patients were randomized to warming with a forced air or an electric warming system.

MEASUREMENT

The number of airborne bacteria was measured using sedimentation agar plates and nitrocellulose membranes at 6 standardized locations in the OR.

MAIN RESULTS

The results of the multivariate analysis showed, that the absence of unidirectional turbulent free laminar airflow and longer duration of surgery increased bacterial counts significantly. The type of patient warming system and the number of health professionals had no significant influence on bacterial counts on any sampling site.

CONCLUSION

ORs with unidirectional turbulent free laminar airflow, and a reduction of surgery time decreased the number of viable airborne bacteria. These factors may be particularly important in critical patients with a high risk for the development of surgical site infections.

Reflective Blankets Are as Effective as Forced Air Warmers in Maintaining Patient Normothermia During Hip and Knee Arthroplasty Surgery

BACKGROUND

The use of forced air warming devices in the operating room has been shown to cause disruption of laminar airflow and a potential for increase in surgical site contamination. In contrast, conductive warming devices such as reflective blankets do not disrupt airflow and therefore have no potential for this increase in surgical site infection. However, some studies have shown them to be inferior to forced air warming devices in maintaining normothermia. We tested the hypothesis that the use of reflective blankets is as effective as forced air warming devices in maintaining intraoperative normothermia after adequate prewarming.

METHODS

We performed a randomized, controlled trial of 50 patients undergoing hip or knee arthroplasty using a protocol of prewarming followed by application of either forced air warming device or a reflective blanket and recording the patients sublingual temperature at a 15-minute interval till arrival in the post-anesthesia care unit.

RESULTS

There was no significant difference in the sublingual temperatures in the 2 groups at any time point.

CONCLUSION

Our study shows that after a period of adequate prewarming, the use of reflective blankets is as effective as the use of forced air warming devices in maintaining normothermia in patients undergoing hip or knee arthroplasty.

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.

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.

Forced-air warming devices and the risk of surgical site infections

The potential that forced-air warming systems may increase the risk of surgical site infections (SSIs) by acting as a vector or causing unwanted airflow disturbances is a concern to health care providers. To investigate this potential, we examined the literature to determine whether forced-air warming devices increase the risk of SSIs in patients undergoing general, vascular, or orthopedic surgical procedures. We examined 192 evidence sources, 15 of which met our inclusion criteria. Most sources we found indirectly addressed the issue of forced-air warming and only three studies followed patients who were warmed intraoperatively with forced-air warming devices to determine whether there was an increased incidence of SSIs. All of the sources we examined contained methodological concerns, and the evidence did not conclusively suggest that the use of forced-air warming systems increases the risk of SSIs. Given the efficacy of these devices in preventing inadvertent perioperative hypothermia, practitioners should continue to use and clean forced-air warming systems according to the manufacturer's instructions until well-conducted, large-scale trials can further examine the issue.

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.

Patient warming excess heat: the effects on orthopedic operating room ventilation performance

BACKGROUND

Patient warming has become a standard of care for the prevention of unintentional hypothermia based on benefits established in general surgery. However, these benefits may not fully translate to contamination-sensitive surgery (i.e., implants), because patient warming devices release excess heat that may disrupt the intended ceiling-to-floor ventilation airflows and expose the surgical site to added contamination. Therefore, we studied the effects of 2 popular patient warming technologies, forced air and conductive fabric, versus control conditions on ventilation performance in an orthopedic operating room with a mannequin draped for total knee replacement.

METHODS

Ventilation performance was assessed by releasing neutrally buoyant detergent bubbles ("bubbles") into the nonsterile region under the head-side of the anesthesia drape. We then tracked whether the excess heat from upper body patient warming mobilized the "bubbles" into the surgical site. Formally, a randomized replicated design assessed the effect of device (forced air, conductive fabric, control) and anesthesia drape height (low-drape, high-drape) on the number of bubbles photographed over the surgical site.

RESULTS

The direct mass-flow exhaust from forced air warming generated hot air convection currents that mobilized bubbles over the anesthesia drape and into the surgical site, resulting in a significant increase in bubble counts for the factor of patient warming device (P < 0.001). Forced air had an average count of 132.5 versus 0.48 for conductive fabric (P = 0.003) and 0.01 for control conditions (P = 0.008) across both drape heights. Differences in average bubble counts across both drape heights were insignificant between conductive fabric and control conditions (P = 0.87). The factor of drape height had no significant effect (P = 0.94) on bubble counts.

CONCLUSIONS

Excess heat from forced air warming resulted in the disruption of ventilation airflows over the surgical site, whereas conductive patient warming devices had no noticeable effect on ventilation airflows. These findings warrant future research into the effects of forced air warming excess heat on clinical outcomes during contamination-sensitive surgery.