Delayed forced air warming prevents hypothermia during abdominal aortic surgery

We have evaluated the efficacy of the delayed forced air warming during abdominal aortic surgery in 18 patients. Patients were allocated randomly to one of two groups: the control group (n = 9) received no intraoperative warming device; the Bair-Hugger group (n = 9) had active skin surface warming with an upper body cover. The device was activated when core temperature decreased to less than 36 degrees C. The reduction in core temperature was 0.6 degrees C during the first hour after induction and 0.4 degrees C during the second hour in both groups. In the control group, core temperature continued to decrease until the end of surgery, whereas in the Bair-Hugger group, the reduction in core temperature stopped after 1 h of warming, and then rewarming began. At the end of surgery, core temperature in the Bair- Hugger group was similar to core temperature before induction, and was higher than core temperature in the control group (P < 0.003).      

The efficacy of carbon-fiber resistive-heating in prevention of core hypothermia during major abdominal surgery

BACKGROUND: Perioperative hypothermia causes numerous severe complications, such as coagulopathy, surgical wound infections, and morbid myocardial outcomes. For prevention of intraoperative hypothermia, an inexpensive, non-disposable carbon fiber resistive warming system has been developed. METHODS: We evaluated the efficacy of resistive-heating, comparing to circulating-water mattress and forced-air warming system. Twenty four patients undergoing elective abdominal surgery were randomly assigned to warming with: 1) a circulating water mattress, 2) a lower-body forced-air system, or 3) a carbon-fiber, resistive-heating blanket. RESULTS: Tympanic membrane temperature in the first two hours of surgery decreased by 1.9 +/- 0.5 degrees C in the water mattress group, 1.0 +/- 0.6 degree C in the forced-air group, 0.8 +/- 0.2 degree C in the resistive-heating group. The decreases in core temperature by the end of surgery were 2.0 +/- 0.8 degrees C in the water mattress group, 0.6 +/- 1.1 degrees C in the forced-air group, and 0.5 +/- 0.4 degree C in the resistive blanket group, respectively. There was no significant difference in the changes of core temperature between the forced-air group and the resistive-heating group. No side effects related to resistive-heating blanket were observed. CONCLUSIONS: Even during major abdominal surgery, carbon-fiber resistive-heating maintains core temperature as effectively as forced air.     

Body heat transfer during hip surgery using active core warming

Canadian Journal of Anesthesia/Journal canadien d'anesthésie - The purpose of this study was to evaluate the effect of core warming on heat redistribution from the core to the periphery as...     

Prevention of hypothermia by cutaneous warming with new electric blankets during abdominal surgery

We have evaluated the efficacy of new electric warming blankets, which meet the requirements of the international standard for perioperative electrical and thermal safety, in preventing intraoperative hypothermia. We studied 18 patients undergoing abdominal surgery, allocated to one of two groups: in the control group, there was no prevention of intraoperative hypothermia (n = 8) and in the electric blanket group, two electric blankets covered the legs and upper body (n = 10). Anaesthesia duration was similar in the two groups (mean 201 (SEM 11) min), as was ambient temperature (20.5 (0.1) degrees C). Core temperature decreased during operation by 1.5 (0.1) degrees C in the control group, but only by 0.3 (0.2) degree C in the electric blanket group (P < 0.01). Five patients shivered in the control group compared with one in the electric blanket group (P < 0.05). We conclude that cutaneous warming with electric blankets was an effective means of preventing intraoperative hypothermia during prolonged abdominal surgery.      

Atropine prevents midazolam-induced core hypothermia in elderly patients.

STUDY OBJECTIVE: To test the hypothesis that core temperature is well preserved when atropine and midazolam are combined. DESIGN: Randomized, blinded study. SETTING: Department of Anesthesia, Yamanashi Medical University. PATIENTS: 40 elderly, ASA physical status I and II patients (aged more than 60 years). INTERVENTIONS: Patients were randomly assigned (n = 10 per group) to premedication with: 1) saline control; 2) midazolam 0.05 mg/kg; 3) atropine 0.01 mg/kg; and 4) midazolam 0.05 mg/kg combined with atropine 0.01 mg/kg. All premedication was given on the ward at approximately 8:30 am, approximately 30 minutes before induction of anesthesia. MEASUREMENTS AND MAIN RESULTS: Core temperatures were measured at the right tympanic membrane. Mean skin temperature was calculated as 0.3 x (T(chest) + T(arm)) + 0.2 x (T(thigh) + T(calf)). Fingertip perfusion was evaluated using forearm minus fingertip and calf minus toe, skin-surface temperature gradients. Temperatures were evaluated at the time of premedication and 30 minutes later, just before induction of anesthesia. Core temperature remained nearly constant in the control patients (0.1 +/- 0.2 degrees C; mean +/- SD), whereas it decreased significantly in the patients given midazolam alone (-0.3 +/- 0.1 degrees C). Atropine alone increased core temperature (0.3 +/- 0.2 degrees C), although the increase was not statistically significant. The combination of midazolam and atropine attenuated the hypothermia induced by midazolam alone (0.0 +/- 0.2 degrees C). Initial skin-temperature gradients exceeded 0 degrees C in all groups, indicating that the patients were vasoconstricted. The gradients were unchanged by premedication with saline or atropine. Midazolam significantly decreased the gradient (-1.8 +/- 1.1 degrees C), as did the combination of midazolam and atropine (-1.4 +/- 0.9 degrees C). CONCLUSIONS: The thermoregulatory effects of benzodiazepine receptor agonist and cholinergic inhibitors oppose each other, and the combination leaves core temperature unchanged.     

Self-warming blanket versus forced-air warming blanket during total knee arthroplasty under spinal anaesthesia: A randomised non-inferiority trial

Background

Arthroplasty patients are at high risk of hypothermia. Pre-warming with forced air has been shown to reduce the incidence of intraoperative hypothermia. There is, however, a lack of evidence that pre-warming with a self-warming (SW) blanket can reduce the incidence of perioperative hypothermia. This study aims to evaluate the effectiveness of an SW blanket and a forced-air warming (FAW) blanket peri-operatively. We hypothesised that the SW blanket is inferior to the FAW blanket.

Methods

In total, 150 patients scheduled for primary unilateral total knee arthroplasty under spinal anaesthesia were randomised to this prospective study. Patients were pre-warmed with SW blanket (SW group) or upper-body FAW blanket (FAW group) set to 38°C for 30 min before spinal anaesthesia induction. Active warming was continued with the allocated blanket in the operating room. If core temperature fell below 36°C, all patients were warmed using the FAW blanket set to 43°C. Core and skin temperatures were measured continuously. The primary outcome was core temperature on admission to the recovery room.

Results

Both methods increased mean body temperature during pre-warming. However, intraoperative hypothermia occurred in 61% of patients in the SW group and in 49% in the FAW group. The FAW method set to 43°C could rewarm hypothermic patients. Core temperature did not differ between groups on admission to the recovery room, p = .366 (CI: −0.18–0.06).

Conclusions

Statistically, the SW blanket was non-inferior to the FAW method. Yet, hypothermia was more frequent in the SW group, requiring rescue warming as we strictly held to the NICE guideline.

Trial Registration

Clinicaltrials.gov identifier: NCT03408197.     

电阻加温垫与充气加温毯预防胸腔镜手术患者低体温效果比较

目的探讨两种加温方式预防胸腔镜手术患者术中低体温的效果。方法将70例胸腔镜手术患者随机分为两组,电阻组(34例)术中采用电阻式碳纤维加温垫加温,充气组(36例)采用充气式加温毯覆盖加温。结果两组各测量时间点患者平均体温均36℃,在麻醉插管、手术开始时、手术开始30 min时电阻组患者体温高于充气组(均P0.01);手术开始1 h后至手术结束,两组体温差异无统计学意义(均P0.05)。结论两种加温方式均能有效预防胸腔镜手术患者术中低体温,其中电阻式碳纤维加温垫维持患者体温更平稳。     

Comparison of two convective warming systems during major abdominal and orthopedic surgery

PURPOSE: Convective warming is routinely employed to maintain perioperative normothermia. However, due to differences in nozzle temperature and air flow of the power units, there are clinically relevant differences in heat transfer among convective warming systems. The purpose of this study was to evaluate the use of a quieter, convective warming system (WarmAir, sound pressure level 49 dba, air flow 35 cfm). The WarmAir system was compared to the standard, higher air flow system (Bair Hugger Model 750, sound pressure level 55 dba, air flow 48 cfm) with regards to temperature outcome. METHODS: Patients undergoing general anesthesia for major abdominal and orthopedic surgery were randomized into one of two groups: WarmAir or Bair Hugger. Both groups received an upper body, convective blanket using coverage appropriate for the given surgical procedure. Convective warming, at the high setting, was started after prepping and draping, and distal esophageal or nasopharyngeal temperature was measured intraoperatively. Sublingual temperature was measured preoperatively and on admission to the postanesthesia care unit. RESULTS: The WarmAir (n = 89) and Bair Hugger (n = 95) groups were similar with respect to age, gender, body mass index, ASA status, fluid balance, and duration of surgery. There was no difference in temperature outcomes between groups. In the WarmAir group, preoperative, lowest intraoperative, end of surgery, and postanesthesia care unit admission temperatures were (means +/- SD); 36.3 +/- 0.5, 35.4 +/- 1.1, 36.4 +/- 0.7, and 36.4 +/- 0.6 degrees C, respectively. Corresponding temperatures in the Bair Hugger group were; 36.3 +/- 0.6, 35.6 +/- 1.0, 36.5 +/- 0.6, and 36.4 +/- 0.5 degrees C, respectively. CONCLUSION: Despite differences in heating characteristics, both convective warming systems were effective in maintaining perioperative normothermia in patients undergoing major abdominal and orthopedic surgery. Therefore, choice of warming system is dependent on other factors such as ergonomics and cost.     

A quality improvement project incorporating preoperative warming to prevent perioperative hypothermia in major burns

Background

Patients with extensive burn injuries are susceptible to a host of accompanying adverse effects should they develop perioperative hypothermia, which occurs in up to ¼ of all major burn cases. This quality improvement project aimed to reduce the incidence of perioperative hypothermia to below 10% of cases in patients with major burn (Total Body Surface Area [TBSA]?>15%), within a one year period.

The effects of warming intravenous fluids on intraoperative hypothermia and postoperative shivering during prolonged abdominal surgery

Background: The infusion of several liters of crystalloid solution at room temperature may significantly contribute to intraoperative hypothermia because warming fluid to core temperature requires body heat. The aim of this study was to evaluate the effect of delivering warmed intravenous (IV) fluid to the patient on preventing intraoperative hypothermia.
Methods: Intraoperative core and mean skin temperatures were measured during prolonged abdominal surgery in 18 patients randomly divided into two groups according to intraoperative IV fluid management. In 9 patients (control group) all IV fluids infused were at room temperature. In the other 9 patients (group receiving warmed fluids) all IV fluids were warmed using an active IV fluid tube-warming system. In all 18 patients a warming blanket covered the skin surface available for cutaneous warming. Intraoperative changes in total body heat content (kJ) were calculated from core and mean skin temperatures.
Results: At the end of surgery, core temperature was 36.7±0.2°C in the group receiving warmed fluids and 35.8±0.2°C in the control group ( P <0.05). The estimated reduction in heat loss provided by warming IV fluid was 217 kJ, a value very close to the theoretical value expected from thermodynamic calculation. During recovery, one patient shivered in the group receiving warmed fluids and seven in the control group ( P <0.05).
Conclusion: In conclusion, infusion of warmed fluids, combined with skin-surface warming, helps to prevent hypothermia and reduces the incidence of postoperative shivering.     

Prevention of hypothermia during hip surgery: effect of passive compared with active skin surface warming

We have measured aural canal (core) and skin temperatures, andbody heat content in 45 patients undergoing elective hip arthroplasty.They received general anaesthesia which included thiopentone,vecuronium and enflurane and nitrous oxide in oxygen. Patientswere allocated randomly to three groups: group 1, control (n= 15), received no intraoperative warming device; group 2 hadpassive skin surface warming (metallized plastic sheet, Thermolite(n = 15); and group 3 had active skin surface warming (forcedheated air, Bair-Hugger) (n = 15). Duration of surgery, fluidadministration and the temperature and relative humidity ofthe operating theatre were similar for the three groups. Coretemperature and mean body heat content decreased significantlyduring surgery in groups 1 and 2 (aural canal temperature 1.5and 1.0°C, and mean body heat content 287 and 189 kJ, respectively),while in group 3 these variables remained near preoperativevalues (P = 0.001). Mean skin and hand temperatures decreasedin the control group, increased in the active warming groupand were unchanged in the passive warming group (P < 0.005),indicating that the forced heated air system was very efficientin providing thermal homeostasis during surgery, while the metallizedplastic sheet was able to insulate the skin only from radiantand convective heat losses, without attenuating the reductionin core temperature.     

Epidural analgesia for major neonatal surgery

Safe effective analgesia for neonates undergoing major surgery remains a challenge particularly in institutions where resources are limited. The experience in the use of epidural analgesia in 240 neonates weighing between 0.9–5.8 kg body weight (lumbar n=211, thoracic n=29) is reviewed. Dural puncture (n=1), convulsion(r)(n=1) and intravascular migration of catheter (n=1) were the only complications. In all cases effective analgesia was established intraoperatively. Postoperatively analgesia was maintained by intermittent ‘top-ups’ (n=170) and continuous infusion (n=10). Skin epidural distance ranged between 3 and 12 mm (mean 6.0±1.7 mm) and did not correlate with the patients’ weight. Patients remained haemodynamically stable except occasional bradycardia below 100 (n=15) which was successfully managed with anticholinergics. The potential risks and benefits of epidural analgesia in this age group are discussed and arguments for intermittent ‘top-up’ doses rather than continuous infusions presented.