Forced-air Warming System Research Articles

Impact of Prewarming on Maintaining Perioperative Body Temperature: A Randomized Clinical Trial

PurposeTo determine the prewarming effect on body temperature in the perioperative period of patients undergoing conventional abdominal surgery and the level of thermal comfort. DesignA randomized controlled clinical trial. MethodsA Brazilian oncology hospital located in São Paulo. A total of 99 patients aged 18 years or over undergoing elective conventional abdominal surgeries, with a minimum duration of 1 hour of anesthesia. The study was carried out from 2019 to 2021. Patients were randomized into 3 groups: prewarming with a blanket and cotton sheet (control; n = 33); prewarming with a forced-air warming system for 20 minutes (intervention 1; n = 33); prewarming with a forced-air warming system for 30 minutes (intervention 2; n = 33). Central temperature was measured by a zero-heat-flux temperature sensor every 20 minutes from the preoperative period until the surgery end time. The level of thermal comfort was determined through self-report during the preanesthetic and postanesthetic periods. FindingsThere was a significant difference between the temperatures between the groups (P = .048), with evidence of greater benefit in maintaining the temperature in the group that received the prewarming intervention for 20 minutes. There was no significant difference between the percentage of temperatures below 36 °C among the groups (P = .135). Patients in the intervention groups were more comfortable during the postanesthetic recovery period than those in the control group (P = .048). Only 7 (8.24%) patients had postoperative chills (P = .399) and more than half of these incidents occurred in the control group (4; 13.3%). ConclusionsPrewarming for 20 minutes obtained the best results, showing the lowest average of temperature episodes below 36 °C during the intraoperative period and greater thermal comfort as reported by patients.

Peripartum Torpor: A Chilling Case Report and Review of the Literature

Purpose: To report a rare case of peripartum maternal hypothermia and bradycardia. Methods: Case report. Results: Torpor is a transient state of hibernation with hypothermia and bradycardia. Hypothermia is defined as an abnormally low core body temperature less than 36°C.1 Sinus bradycardia is defined as less than 60 beats/min. While occasionally hypothermia or bradycardia is seen in obstetric patients undergoing vaginal delivery, when combined together, it can be a rare, life-threatening state that requires prompt intervention to prevent adverse maternal and fetal outcomes. A 23 year-old G2P0102 at 33+3 weeks of gestation was admitted to the high risk obstetric service for preterm labor complicated by fetal growth restriction. She had a history of preeclampsia in a previous pregnancy, but otherwise denied any chronic medical problems. Upon arrival, her vital signs showed a temperature of 37°C, a pulse of 53 bpm, and blood pressure of 126/62 mmHg. Her white blood cell count was 12.4 x 109/L and hemoglobin was 11.3 g/dL. She received betamethasone for fetal lung maturity and penicillin for Group B streptococcus prophylaxis. As her cervix continued to dilate, she received an epidural for pain management. Once she was in active labor, she became bradycardic with a pulse in the 30s-40s bpm, as confirmed by EKG. She was completely asymptomatic at this time, and fetal heart tones were reassuring with a baseline between 110’s-130’s bpm. She delivered vaginally with 150 mL of estimated blood loss, and her bradycardia continued postpartum even after the epidural was discontinued. When she complained of feeling cold, multiple attempts with different oral and axillary thermometers could not obtain a reading. She was warmed with forced-air warming blankets, warmed blankets, and hot packs in her groin and axilla. During this time, discussion with the NICU staff revealed that her baby was also hypothermic at 33.3°C and hypoglycemic at 28 mg/dL at birth. Other than feeling cold, the patient continued to be asymptomatic despite hypotension and bradycardia. She appeared somnolent but was responsive to questions. Her uterus was firm with minimal vaginal bleeding and no purulent or foul-smelling vaginal discharge. Repeat laboratory testing revealed a white blood count of 19 x 109/L and lactate was 3.3 mmol/L. Her comprehensive metabolic panel was unremarkable. A chest x-ray was clear. A C-reactive protein was < 0.3 mg/dL and sedimentation rate was 14 mm/h. A rectal continuous thermometer was placed, which eventually recorded a temperature at 33.3°C and upon recheck was 31.7°C. A multidisciplinary team, including Anesthesia, Internal Medicine, and Neurology, evaluated the patient due to concern for a central nervous system insult. She received fluid resuscitation and broad-spectrum antibiotics for sepsis protocol. Due to the concern for potential septic shock, the decision was made to transport her to the Medical ICU for further management. As she was leaving Labor & Delivery, her temperature had increased to 36.9°C and her pulse to 61. Thyroid studies the next day revealed a normal Free T4 of 1.00 ng/dL and a high thyroid stimulating hormone level of 9.55 uIU/mL. However, despite an extensive workup, no clear etiology of her hypothermia and bradycardia was identified. Intervention with fluids and application of forced-air warming system resolved the hypothermia in less than 6 hours without relapse. Antibiotics were discontinued after one day due to low suspicion for systemic infection. She remained vitally stable and was discharged on postpartum day 2 without further complications. Conclusions: Maternal hypothermia is relatively common during cesarean delivery; however, very few cases report maternal hypothermia during vaginal delivery. An English language literature search for maternal hypothermia during vaginal delivery yielded less than 10 case reports – few of which identified a cause of the hypothermia – and none of which reported simultaneous maternal bradycardia. While our case is a very rare presentation and the etiology is still unknown, it highlights the importance of prompt recognition of vital sign derangements in peripartum patients as well as multidisciplinary attention.

Perioperative cutaneous complications in an elderly patient due to inappropriate use of a forced-air warming device and underbody blanket: a case report

Forced-air warming is commonly utilized to prevent perioperative hypothermia. Underbody warming blankets are often employed to secure a larger area for patient warming. While forced-air warming systems are generally regarded as safe, improper usage poses a risk of cutaneous complications. Additionally, the influence of underbody blankets on cutaneous complications remains uncertain. We present a case of cutaneous complications resulting from the improper utilization of a forced-air warming device and an underbody blanket. A 79-year-old man presented to the hospital for robotic proctectomy under general anesthesia. The surgery lasted for 7 hours, and the forced-air warming device with underbody blanket operated continuously for 5 hours intraoperatively. The surgery was completed without any incidents. However, first-degree burns on the patient’s back, along with superficial decubitus ulcers on his right scapula, were observed after surgery. To prevent cutaneous complications, clinicians must adhere to the manufacturer's guidelines when utilizing a forced-air warming system. Compared to overbody blankets, underbody blankets have limitations in monitoring cutaneous responses. Ensuring patient safety requires selecting an appropriate blanket for scheduled operations.

The effects of forced air warming system on the hemodynamic status, pain intensity, tremors, nausea and vomiting in candidates of emergency laparotomy patients: a double-blind randomized clinical trial

Objective: During emergency laparotomy surgeries, a wide incision is usually created in the abdomen causing the exposure of visceral organs to cold temperatures in the operation room. Other factors such as excessive stress, intra-operation blood transfusion, and prolonged anesthesia increase the risk of hypothermia in these patients. In this study, we studied the effects of forced air warming systems on the hemodynamic status, pain intensity, tremors, nausea and vomiting in emergency laparotomy patients.
 Methods: In the present double-blinded clinical trial, 80 candidates for emergency laparotomy were randomized into two groups: intervention (patients receiving forced air warming during anesthesia) and control (patients without an active warming system). Patients’ hemodynamic status (during anesthesia and at post anesthesia care unit (PACU), pain intensity, opioids received, tremors, nausea, vomiting, and antiemetics administration were compared between the two groups.
 Results: The amounts of opioids (P=0.041) and relaxants (P=0.039) received by the patients were significantly lower in the intervention group than in the control group. The hemodynamic status was more stable in the patients of the intervention group than those in the control group at all times measured. Pain intensity (per minute) at the PACU was significantly higher in the control group than in the intervention group (P=0.041). Among the patients admitted to the PACU, participants with no tremors (P=0.005) or nausea (P=0.005) were significantly higher in the intervention group than in the control group. Also, in the recovery unit, patients in the intervention group received significantly lower amounts of opioids (i.e., mg of pethidine, P=0.036) and antiemetics (P=0.011) compared to the control group.
 Conclusion: The use of a forced air warming system in the operation room stabilizes the hemodynamic status and reduces the pain intensity, tremors, nausea and vomiting in emergency laparotomy patients. As a non-pharmacological strategy, this method was observed to have satisfactory safety.

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 objectiveThe 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. DesignSystematic review and network meta-analysis. SettingOperating room. InterventionFive 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. MeasurementsThe 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. ResultsThis 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. ConclusionsThe 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.

Resistive Warming Mattress, Forced-Air Warming System, or a Combination of the Two in the Prevention of Intraoperative Inadvertent Hypothermia: A Randomized Trial

To prevent intraoperative inadvertent hypothermia (IIH), resistive products and forced-air warming systems are often used simultaneously. There is insufficient evidence to show whether this application is clinically more effective than a single active warming device. The aim of this study is to compare the efficacy a single intraoperative active warming method with combined methods in IIH prevention. A randomized, prospective, experimental study. This study was conducted between June and October 2021 in the operating room of a training and research hospital. The study sample consisted of 123 patients who underwent scheduled orthopedic surgery under spinal anesthesia, were young (18-64), and had an ASA risk score of I to III. The patients were divided into three groups preoperatively according to the stratified randomization technique. To prevent IIH, a resistive warming mattress was used in group 1; a forced-air warming system was used in group 2; and a combination of the two methods were used in group 3. The body temperatures of the patients were measured and recorded every 15 minutes from admission to the operating room until the end of surgery. The mean intraoperative body temperature of the patients was 36.6±0.15˚C for group 1; 36.6±0.1˚C for Group 2 and 36.6 ± 0.15˚C for Group 3. There was no difference between the groups in terms of body temperature. The overall incidence of IIH was 8.1%; 9.8% in group 1, 9.8% in group 2 and 4.9% in group 3. There was no statistically significant difference between the groups in terms of IIH (p < .05). This study supports the efficacy of using resistive warming mattress and forced-air warming systems in preventing IIH. The use of both methods together made no difference in terms of IIH development.

Efficacy and Safety of Forced-Air Warming System versus Passive Warming Measures in Major Surgeries: A Systematic Review

Purpose: To compare the clinical impact of forced-air warming system (Bair HuggerTM, BH) and passive warming measures in major surgery patients. Methods: Databases including Pubmed, Cochrane Library, Clinical Trials.Gov and CNKI were searched to collect studies published before January 2019 that were concerned the clinical effects of Bair Hugger. Two reviewers independently screened the literatures, extracted the data. The revised Jadad scale was used to evaluate the methodological quality of the literatures. Meta-analysis was performed by using Review Manager 5.3.0. Findings: A total of 27 studies were included. The result of meta-analysis showed that BH had a significant advantage in rate of hypothermia (RD = -0.42, 95%CI (-0.68, -0.16)) , shivering (RD = -0.28, 95%CI (-0.43, -0.13)), anesthesia recovery time (MD = -8.27, 95% CI (-13.49, -3.05)), hospital stay (MD = -1.27, 95% CI (-2.05) , -0.48)), while incision infection RD = -0.15, 95%CI (-0.40,0.11)) , intraoperative blood loss (MD = -16.88, 95%CI(-34.73,0.96)), intraoperative blood transfusion (MD = -41.49, 95% CI( -108.36, 25.38)) , pain RD = -0.02, 95%CI(-0.08, 0.03)) and other complications (RD = -0.13, 95%CI(-0.39,0.12)) had an advantage but not significant. Subgroup analyses showed that operation mode and operation duration was the sensitive factors. Conclusion: Compared to passive warming, Bair Hugger has significant advantages in hypothermia protection and further reduces the risk of incision chills and prolonged hospital stay. Combined with the current status of body temperature protection in China, it is necessary to enhance the awareness of body temperature protection, standardize medical behavior, and increase the popularity of active warming systems.

A STUDY OF WARMING DEVICES AND PERIOPERATIVE FACTORS POTENTIALLY CONTRIBUTING TO SURGICAL FIELD CONTAMINATION IN SMALL ANIMAL PATIENTS

Bacterial contamination on surgical drapes may increase the risk of surgical site infection (SSI). This preliminary investigation analyzed the relationship between forced-air warming devices and bacterial contamination on surgical drapes in small animal soft tissue surgery settings. The subjects of this study were canine and feline patients enrolled in clean surgical procedures at the National Taiwan University Veterinary Hospital. Bacterial colonies on surgical drapes were sampled on agar plates immediately prior to and 1[Formula: see text]h after skin incision. Cases with bacteria growth on the post-incision sampled agar were considered with surgical field contamination (SFC). Intraoperative warming methods (forced-air warming systems or circulating water blankets) and other factors that potentially contribute to SFC (drape material, patient features, surgical procedure types, surgeons, and number of operating room personnel) were recorded. The study comprised 57 operations, 28 cases belonged to the circulating water blanket group and 29 belonged to the forced-air warming system group. No differences in contamination rate were detected among intraoperative warming methods, drape materials, patient characteristics, surgical procedure types, or number of operating room personnel. However, a significant difference in contamination rate was detected among surgeons.

Comparison of Warm Touch Forced Air Warming System vs Routine Care in Increasing Tympanic Temperature and FOUR Score

Comparison of Warm Touch Forced Air Warming System vs Routine Care in Increasing Tympanic Temperature and FOUR Score

Effects of a preoperative forced-air warming system for patients undergoing video-assisted thoracic surgery: A randomized controlled trial.

Background:The incidence of intraoperative hypothermia is still high despite the proposal of different preventive measures during thoracoscopic surgery. This randomized control study evaluated the effects of 30-minute prewarming combined with a forced-air warming system during surgery to prevent intraoperative hypothermia in patients undergoing video-assisted thoracic surgery under general anesthesia combined with erector spinae nerve block.Methods:Ninety-eight patients were randomly and equally allocated to prewarming or warming groups (n = 49 each). The primary outcome was the incidence of intraoperative hypothermia. Secondary outcomes were core temperature, irrigation and infused fluid, estimated blood loss, urine output, type of surgery, intraoperative anesthetic dosage, hemodynamics, recovery time, the incidence of postoperative shivering, thermal comfort, postoperative sufentanil consumption and pain intensity, patient satisfaction, and adverse events.Results:The incidence of intraoperative hypothermia was significantly lower in the prewarming group than the warming group (12.24% vs 32.65%, P = .015). Core temperature showed the highest decrease 30 minutes after surgery start in both groups; however, the rate was lower in the prewarming than in the warming group (0.31 ± 0.04°C vs 0.42 ± 0.06°C, P < .05). Compared with the warming group, higher core temperatures were recorded for patients in the prewarming group from T1 to T6 (P < .05). Significantly fewer patients with mild hypothermia were in the prewarming group (5 vs 13, P = .037) and recovery time was significantly reduced in the prewarming group (P < .05). Although the incidence of postoperative shivering was lower in the prewarming group, it was not statistically significant (6.12% vs 18.37%, P = .064). Likewise, the shivering severity was similar for both groups. Thermal comfort was significantly increased in the prewarming group, although patient satisfaction was comparable between the 2 groups (P > .05). No adverse events occurred associated with the forced-air warming system. Both groups shared similar baseline demographics, type of surgery, total irrigation fluid, total infused fluid, estimated blood loss, urine output, intraoperative anesthetic dosage, hemodynamics, duration of anesthesia and operation time, postoperative sufentanil consumption, and pain intensity.Conclusion:In patients undergoing video-assisted thoracic surgery, prewarming for 30 minutes before the induction of anesthesia combined with a forced-air warming system may improve perioperative core temperature and the thermal comfort, although the incidence of postoperative shivering and severity did not improve.

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

BackgroundAbout 50% patients who underwent off-pump coronary artery bypass grafting (OPCAB) experienced perioperative hypothermia. Pre-warming and intraoperative infusion of amino acid injection are the most popular perioperative insulation measures in recent years, but neither of them can completely prevent intraoperative hypothermia. The objective is to investigate the effect of preoperative warming and/or intraoperative infusion of amino acid injection on body temperature in patients undergoing OPCAB.MethodsA prospective, double blind, randomized controlled, single-center study. Seventy-two patients were randomly divided into 4 groups: control group, pre-warming group, amino-acid group and multi-mode group. Pre-warming and multi-mode group were pre-heated with warming blankets and forced-air warming system before induction. After that, amino-acid and multi-mode group were infused with 18-amino acid solution. The perioperative temperature and complications were monitored.ResultsThe temperature of control and amino-acid group decreased significantly, but amino-acid group recovered to preoperative level faster. The temperature of pre-warming group was stable, and that in multi-mode group increased at 60 min after the start of surgery. There was a significant difference in temperature at each time, and no difference in the incidence of complications between the groups.ConclusionsPreoperative warming and/or intraoperative infusion of amino acid injection can effectively reduce hypothermia in OPCAB surgery. Pre-warming before anesthesia is more effective, and the combination of the two methods has the best effect.

Effect of rewarming and homeostasis of groin-mediated forced-air warming system in patients with hypothermia after cardiopulmonary bypass

Objective To investigate the rewarming effect of groin-mediated forced-air warming system in patients with hypothermia after cardiopulmonary bypass. Methods A total of 100 hypothermia patients after cardiopulmonary bypass were divided into observation group and control group with 50 cases each by random digits table method. Patients in control group received pelma-mediated forced-air warming system, observation group carried out groin-mediated forced-air warming system. The levels of bladder temperature, axillary temperature and lactate concentration were monitored at 10 min (T10), 30 min (T30), 60 min (T60), 90 min (T90) after rewarming in two groups, rewarming time and drainage volume at 90 min after rewarming between two groups was also compared. Results Bladder temperature in observation group were (34.44±0.98), (35.44±1.12), (36.71±1.16), (37.60±1.45) ℃ at T10, T30, T60, T90, axillary temperature were (34.30±1.85), (35.31±1.36), (36.38±1.57), (37.28±1.72) ℃, bladder temperature and axillary temperature in control group were (34.18±1.56), (36.91±1.61), (37.70±1.29), (37.40±1.10) ℃ and (34.45±1.03), (36.30±1.25), (37.70±1.23), (37.19±1.31) ℃, respectively. There was no significant difference in bladder temperature and axillary temperature at T10 and T90 (P>0.05), however, the bladder temperature and axillary temperature was significantly decreased in observation group compared to control group at T30 and T60 (t value was 5.309, 4.073, P 0.05), however, the lactate concentration was significantly decreased in observation group compared to control group at T60 and T90 (t value was 7.276, 8.640, P<0.01), in addition, there were crossover effect of time and grouping factor in lactate concentration (F value was 36.034, P<0.01). Drainage volume at 90 min after rewarming were (95.44±15.24) ml in observation group, (106.08±25.56) ml in control group, the difference was significant between two groups (t value was 2.528, P<0.05). Conclusions Groin-mediated forced-air warming system can effectively and uniformly rewarming the body temperature of patients with hypothermia after cardiopulmonary bypass and served as a potential rewarming strategy. Key words: Cardiopulmonary bypass; Forced-air rewarming; Bladder temperature; Axillary temperature

PIN67 BUDGET IMPACT ANALYSIS OF THE IMPLEMENTATION OF A PRESURGICAL WARMING PROTOCOL TO EFFECTIVELY MANAGE SURGICAL PATIENT NORMOTHERMIA

Perform a budget impact analysis from a hospital perspective and estimate the cost savings achieved by adding a presurgical warming protocol to intra-operative warming, using a forced-air warming system to prevent inadvertent perioperative hypothermia (IPH). The one-year time horizon budget impact model is based on a new static decision-tree, modified from a model published by NICE in 2008. Based on IPH rate, the model allows a comparison of different patient temperature management strategies with associated material and adverse consequences costs. The current analysis uses IPH rates measured in a German hospital when implementing active pre-warming plus intra-operative warming versus intra-operative warming only. Adverse consequences of IPH, according to the NICE guidance, are grouped in surgical site infections (SSI), morbid cardiac events (MCE) and other complications, including the need of blood transfusions. The cost of the adverse consequences is monetized via increased length-of-stay (LOS). The model accounts for minor, intermediate and major surgery and four different age groups following German DRG-data to evaluate the relative risk for SSI and MCE. The costs of a bed-day on a surgical ward are derived from WHO estimates. The hypothermia rate from a retrospective study including 7786 patients having a surgery duration of at least 30 minutes under general anesthesia showed an IPH decrease from 12.4% to 5.1% with the introduction of active pre-warming in addition to intra-operative warming. For a hypothetical hospital conducting 1,000 surgical procedures per year (48% minor, 30% intermediate and 22% major), the implementation of pre-warming could result in total annual cost savings of 192,220€, corresponding to 60% direct costs decrease, 300 less hypothermia events and 342 days reduction in attributable LOS. The implementation of pre-warming is a cost saving intervention and should be recommended for effective management of patient normothermia.

Comparison of Electric Resistive Heating Pads and Forced-Air Warming for Pre-hospital Warming of Non-shivering Hypothermic Subjects.

Victims of severe hypothermia require external rewarming, as self-rewarming through shivering heat production is either minimal or absent. The US Military commonly uses forced-air warming in field hospitals, but these systems require significant power (600-800 W) and are not portable. This study compared the rewarming effectiveness of an electric resistive heating pad system (requiring 80 W) to forced-air rewarming on cold subjects in whom shivering was pharmacologically inhibited. Shivering was inhibited by intravenous meperidine (1.5 mg/kg), administered during the last 10 min of cold-water immersion. Subjects then exited from the cold water, were dried and lay on a rescue bag for 120 min in one of the following conditions: spontaneous rewarming only (rescue bag closed); electric resistive heating pads (EHP) wrapped from the anterior to posterior torso (rescue bag closed); or, forced-air warming (FAW) over the anterior surface of the body (rescue bag left open and cotton blanket draped over warming blanket). Supplemental meperidine (to a maximum cumulative dose of 3.3 mg/kg) was administered as required during rewarming to suppress shivering. Six healthy subjects (3 m, 3 f) were cooled on three different occasions, each in 8°C water to an average nadir core temperature of 34.4 ± 0.6°C (including afterdrop). There were no significant differences between core rewarming rates (spontaneous; 0.6 ± 0.3, FAW; 0.7 ± 0.2, RHP; 0.6 ± 0.2°C/h) or post-cooling afterdrop (spontaneous; 1.9 ± 0.4, FAW; 1.9 ± 0.3, RHP; 1.6 ± 0.2°C) in any of the 3 conditions. There were also no significant differences between metabolic heat production (S; 74 ± 20, FAW; 66 ± 12, RHP; 63 ± 9 W). Total heat gain was greater with FAW (36 W gain) than EHP (13 W gain) and spontaneous (13 W loss) warming (p < 0.005). Total heat gain was greater in FAW than both EHP, and spontaneous rewarming conditions, however, there were no observed differences found in rewarming rates, post-cooling afterdrop or metabolic heat production. The electric heat pad system provided similar rewarming performance to a forced-air warming system commonly used in US military field hospitals for hypothermic patients. A battery-powered version of this system would not only relieve pressure on the field hospital power supply but could also potentially allow extending use to locations closer to the field of operations and during transport. Such a system could be studied in larger groups in prospective trials on colder patients.

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

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

Effect of forced-air warming system in prevention of postoperative hypothermia in elderly patients: A Prospective controlled trial.

Background:Postoperative hypothermia in elderly patients is a well-known serious complication as it impairs wound healing, induces coagulopathy, increases the risk of blood loss, enhances oxygen consumption, and precipitates cardiac arrhythmias. We conducted this randomized controlled trial to evaluate the effect of a forced-air warming system on rewarming elderly patients undergoing total knee or hip arthroplasty.Methods:We recruited 243 elderly patients undergoing total knee or hip arthroplasty between May and December 2016. They were divided into three groups according to a computer-generated randomization table: group C (n = 78, rewarmed with only a regular blanket), group F1 (n = 82, rewarmed with a forced-air warming system set at 38°C), and group F2 (n = 83, rewarmed with a forced-air warming system set at 42°C). The nasopharyngeal temperature was recorded every 5 min for the first half hour, then every 10 min up to the end of the PACU (postanesthesia care unit) stay. The primary outcome was the rewarming time. The rewarming rate, increase in nasopharyngeal temperature (compared to the start of rewarming), hemodynamics, recovery time, and incidences of adverse effects were recorded.Results:No significant differences were found among the three groups in terms of the baseline clinical characteristics, use of narcotic drugs, intraoperative temperature, and hemodynamics (P > .05). Compared with the elderly patients in groups C and F1, both the heart rate and mean arterial pressure of those in group F2 were significantly increased 20 min after arrival at the PACU (P < .05). Patients in group F2 had the shortest rewarming time (35.89 ± 6.45 min, P < .001), highest rewarming efficiency (0.028 ± 0.001°C/min, P < .001), and fastest increased nasopharyngeal temperature among the three groups. Moreover, the elderly patients in group F2 had lower incidences of arrhythmia and shivering (P < .05).Conclusions:The use of a forced-air warming system set at 42°C was shown to be the most effective way of rewarming elderly patients with postoperative hypothermia.

Evaluation of Warming Effectiveness on Physiological Indices of Patients Undergoing Laparoscopic Cholecystectomy Surgery: A Randomized Controlled Clinical Trial

The present study aimed to evaluate the impact of warming onphysiological indices of patients undergoing laparoscopic cholecystectomy. The study was a three-group randomized controlled clinical trial. In the present study, 96 patients were assigned to three groups: forced-air warming system group; warmed intravenous fluid group; and control group. The intervention was performed immediately after the anesthesia induction. Physiological indices (core body temperature, blood pressure, and heart rate) were evaluated at 15-minute intervals, and postoperative shivering was also recorded. The mean systolic blood pressure and the mean heart rate were significantly different in each warming group before, during, and after surgery, but the three groups had no significant differences in terms of physiological indices at any time (P > .05). Postoperative shivering was not seen in any group. Both interventions had similar effects on physiological indices. Therefore, the recommendation is to use the warming method according to patient's other conditions.

Effect of intraoperative warming on delirium during emergence from general anesthesia in elderly patients

Objective To evaluate the effect of intraoperative warming on delirium during emergence from general anesthesia in elderly patients. Methods Eighty elderly patients of both sexes, aged≥65 yr, of American Society of Anesthesiologists physical statusⅠ-Ⅲ, scheduled for elective total hip replacement, were assigned to routine group (group R, n=40) and warming group (group W, n=40). The non-operated site was covered using the sterile cloth, and no other active warming measurements were given in group C. Fluid was infused and warmed to 37 ℃, the non-operated site was covered using the forced-air warming system, and the temperature of the forced-air warming system was maintained at 38-42 ℃ in group W. The tympanic membrane temperatures was recorded at 5 min after anesthesia induction, at 30, 60 and 90 min after beginning of surgery, at the end of surgery and at 30 min after emergence from anesthesia, and the difference between monitored values and monitored values on admission to operating room (△T) was recorded at each time point. The intraoperative volume of fluid infused, operation time, extubation time, duration of postanesthesia care unit stay and development of delirium during emergence and shivering were recorded. Results Compared with group R, △T was significantly decreased at 60 and 90 min after beginning of surgery, the incidence of delirium during emergence and shivering was decreased, the extubation time and duration of postanesthesia care unit stay were shortened in group W (P<0.05). Conclusion Intraoperative warming can decrease the development of delirium during emergence from general anesthesia and is helpful in improving the quality of recovery from anesthesia in elderly patients. Key words: Body temperature; Aged; Anesthesia recovery period; Delirium

Forced Air Warming System: Evaluation of Internal System Contamination.

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. 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. 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. 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.

Comparative evaluation of forced air warming and infusion of amino acid-enriched solution on intraoperative hypothermia in patients undergoing head and neck cancer surgeries: A prospective randomised study.

Background:Inadvertent core hypothermia is a common occurrence during general anaesthesia. Forced air warming (FAW) is the most effective perianaesthetic warming system, but it may lead to thermal discomfort. Amino acids (AAs) have been used to prevent hypothermia, but no study has compared the effect of AA infusion with FAW systems. We have conducted this study to compare the effects of external heating (FAW system) and internal heat generation (AA infusion) in preventing hypothermia during anaesthesia.Methods:After institutional review board approval, 80 American Society of Anesthesiologists Grade I/II adult patients admitted for head and neck cancer surgeries lasting more than 2 h under general anaesthesia were included. The patients were randomly divided into two groups using computer-generated codes to receive AA infusion at 3 mL/kg/h, Group AA (N = 40), or normal saline at 3 mL/kg/h with FAW, Group FA (N = 40) till the end of surgery. Standard anaesthetic technique and monitoring was used in all the patients.Results:The baseline mean temperature in both the groups was comparable. The core temperature was similar in the two groups at 30 min (35.6 ± 0.54 vs 35.5 ± 0.54), 60 min (35.5 ± 0.63 vs 35.3 ± 0.60), 90 min (35.5 ± 0.79 vs 35.2 ± 0.66), 120 min (35.6 ± 0.93 vs 35.2 ± 0.78), 150 min (35.7 ± 0.88 vs 35.3 ± 0.89) and 180 min (35.8 ± 1.01 vs 35.3 ± 0.95) in Groups FA and AA, respectively (P > 0.05). However, the core temperature was significantly higher in Group FA at 210 min (35.8 ± 1.0 vs 35.3 ± 0.85; P = 0.01), 240 min (35.9 ± 1.0 vs 35.4 ± 0.90; (P = 0.001), 270 min (35.9 ± 1.12 vs 35.6 ± 0.97; P = 0.002) and 300 min (36.0 ± 1.12 vs 35.6 ± 1.02; P = 0.002), respectively. Clinically relevant hypothermia (at least one measurement <35.5°C) was comparable between the two groups.Conclusion:The AA infusion can be used as an alternative to FAW in preventing intraoperative hypothermia under general anaesthesia especially in places where FAW system is unavailable.