Core temperatures during major abdominal surgery in patients warmed with new circulating-water garment, forced-air warming, or carbon-fiber resistive-heating system.

PURPOSE: It has been reported that recently developed circulating-water garments transfer more heat than a forced-air warming system. The authors evaluated the hypothesis that circulating-water leg wraps combined with a water mattress better maintain intraoperative core temperature ≥36°C than either forced-air warming or carbon-fiber resistive heating during major abdominal surgery. METHODS: Thirty-six patients undergoing open abdominal surgery were randomly assigned to warming with: (1) circulating-water leg wraps combined with a full-length circulating-water mattress set at 42°C, (2) a lower-body forced-air cover set on high (≈43°C), and (3) a carbon-fiber resistive-heating cover set at 42°C. Patients were anesthetized with general anesthesia combined with continuous epidural analgesia. The primary outcome was intraoperative tympanic-membrane temperature ≥36°C. RESULTS: In the 2 h after anesthesia induction, core temperature decreased 1.0 ± 0.5°C in the forced-air group, 0.9 ± 0.2°C in the carbon-fiber group, and 0.4 ± 0.4°C in the circulating-water leg wraps and mattress group (P < 0.05 vs. forced-air and carbon-fiber heating). At the end of surgery, core temperature was 0.2 ± 0.7°C above preoperative values in the circulating-water group but remained 0.6 ± 0.9°C less in the forced-air and 0.6 ± 0.4°C less in the carbon-fiber groups (P < 0.05 vs. carbon fiber). CONCLUSIONS: The combination of circulating-water leg wraps and a mattress better maintain intraoperative core temperature than did forced-air and carbon-fiber warming systems.

[Reliability of propofol target-controlled infusion in obese patients].

BACKGROUND: Propofol target-controlled infusion (TCI) is now commonly used for induction and maintenance of anesthesia. In this study, we measured the propofol plasma concentrations in obese patients in order to test our hypothesis that propofol TCI is reliable for use in obese patients. METHODS: We measured plasma concentrations of propofol in 10 obese patients undergoing elective general anesthesia. Propofol TCI was commenced at a target plasma concentration of 4microg x ml(-1) using a TCI pump. The target concentration was kept at 4microg x ml(-1) for at least 3 hours. Arterial blood samples were drawn for measurement of the propofol plasma-concentration analysis at 30, 60, 90, 120 and 180 minutes after the induction of anesthesia, and at the emergence from anesthesia. RESULTS: The measured plasma concentrations of the drug were not significantly different from the target plasma concentrations and they showed no tendency to increase during the 3 hours of anesthesia. The measured plasma concentration at emergence was lower than the estimated value. CONCLUSIONS: We conclude that propofol TCI is a reliable method for maintaining anesthesia even in obese patients. At emergence, however, the data suggested that the plasma concentrations might be lower than the estimated values in obese patients.

Fever during anaesthesia.

Fever occurs when pyrogenic stimulation activates thermal control centres. Fever is common during the perioperative period, but rare during anaesthesia. Although only a limited number of studies are available to explain how anaesthesia affects fever, general anaesthesia seems to inhibit fever by decreasing the thermoregulatory-response thresholds to cold. Opioids also inhibit fever; however, the effect is slightly less than that of general anaesthesia. In contrast, epidural anaesthesia does not affect fever. This suggests that hyperthermia, which is often associated with epidural infusions during labour or in the post-operative period, may be a true fever caused by inflammatory activation. Accordingly, this fever might be diminished in patients who receive opioids for pain treatment. Post-operative fever is a normal thermoregulatory response usually of non-infectious aetiology. Fever may be important in the host defence mechanisms and should not be routinely treated lest the associated risks exceed the benefits.

[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.

Resistive-heating and forced-air warming are comparably effective.

UNLABELLED: Serious adverse outcomes from perioperative hypothermia are well documented. Consequently, intraoperative warming has become routine. We thus evaluated the efficacy of a novel, nondisposable carbon-fiber resistive-heating system. Twenty-four patients undergoing open abdominal surgery lasting approximately 4 h were randomly assigned to warming with 1) a full-length circulating water mattress set at 42 degrees C, 2) a lower-body forced-air cover with the blower set on high, or 3) a three-extremity carbon-fiber resistive-heating blanket set to 42 degrees C. Patients were anesthetized with a combination of continuous epidural and general anesthesia. All fluids were warmed to 37 degrees C, and ambient temperature was kept near 22 degrees C. Core (tympanic membrane) temperature changes among the groups were compared by using factorial analysis of variance and Scheffé F tests; results are presented as means +/- SD. Potential confounding factors did not differ significantly among the groups. In the first 2 h of surgery, core temperature decreased by 1.9 degrees C +/- 0.5 degrees C in the circulating-water group, 1.0 degrees C +/- 0.6 degrees C in the forced-air group, and 0.8 degrees C +/- 0.2 degrees C in the resistive-heating group. At the end of surgery, the decreases were 2.0 degrees C +/- 0.8 degrees C in the circulating-water group, 0.6 degrees C +/- 1.0 degrees C in the forced-air group, and 0.5 degrees C +/- 0.4 degrees C in the resistive-heating group. Core temperature decreases were significantly greater in the circulating-water group at all times after 150 elapsed minutes; however, temperature changes in the forced-air and resistive-heating groups never differed significantly. Even during major abdominal surgery, resistive heating maintains core temperature as effectively as forced air. IMPLICATIONS: Efficacy was similar for forced-air and resistive heating, and both maintained intraoperative core temperature far better than circulating-water mattresses. We thus conclude that even during major abdominal surgery, resistive heating maintains core temperature as effectively as forced air.