Body morphology and the speed of cutaneous rewarming.

Background: Infants and children cool quickly because their surface area land therefore heat loss) is large compared with their metabolic rate, which is mostly a function of body mass. Rewarming rate is a function of cutaneous heat transfer plus metabolic heat production divided by body mass. Therefore, the authors tested the hypothesis that the rate of forced-air rewarming is inversely related to body size. Methods: Isoflurane, nitrous oxide, and fentanyl anesthesia were administered to infants, children, and adults scheduled to undergo hypothermic neurosurgery. All fluids were warmed to 37 degreesC and ambient temperature was maintained near 21 degreesC, Patients were covered with a full-body, forced-air cover of the appropriate size. The heater was set to low or ambient temperature to reduce core temperature to 34 degreesC in time for dural opening. Blower temperature was then adjusted to maintain core temperature at 34 degreesC for 1 h, Subsequently, the forced-ak heater temperature was set to high (approximate to 43 degreesC). Rewarming continued for the duration of surgery and postoperatively until core temperature exceeded 36.5 degreesC. The rewarming rate in individual patients was determined by linear regression. Results: Rewarming rates were highly linear over time, with correlations coefficients (r(2)) averaging 0.98 +/- 0.02. There was a Linear relation between rewarming rate (degreesC/h) and body surface area (BSA; m(2)): Rate (degreesC/h) = -0.59 (.) BSA(m(2)) + 1.9, r(2) = 0.74. Halving BSA thus nearly doubled the rewarming rate. Conclusions: Infants and children rewarm two to three times faster than adults, thus rapidly recovering from accidental or therapeutic hypothermia.