Warming with a forced air warming blanket minimizes anesthetic-induced hypothermia in cats

Objective-To evaluate the effectiveness of a forced-air warming blanket (FAWB) in minimizing anesthetic-induced hypothermia in cats, and to examine the relationship between esophageal and other estimates of body temperature during skin surface warming. Study Design-Prospective, randomized cross-over trial. Animals-Eight adult domestic shorthair cats (four males and four females) weighing 2.3 to 4.5 kg. Methods-Each cat was anesthetized with halothane in oxygen on four occasions and covered with a modified FAWB. Air delivered to the cats by the FAWB was warmed to approximately 43 degrees C. Each trial lasted 90 minutes and was divided into two consecutive 45-minute periods, during which the FAWB was activated or inactivated thus creating four treatment trials: off/off, on/off, on/on, off/on. Measurements of body temperature from the caudal esophagus, deep rectum, toe-web, and tympanic membrane were recorded at regular intervals throughout each trial and compared. Results-A steady decline in body temperature was observed throughout each trial. Mean body temperature in the cats receiving continual skin surface warming (on/on) was significantly higher than in those receiving no active warming (off/off) and those receiving delayed warming (off/on), from 45 minutes onwards. By 90 minutes, the mean body temperature of cats warmed continuously was 0.9 degrees C higher than in those with no active warming. Notable differences in body temperature were detected between all measurement sites, with the exception of esophagus versus rectum. Rectal and esophageal temperatures did not differ at any time point. Tympanic membrane temperatures measured with either device were lower than esophageal temperatures. Conclusions-The modified FAWB was effective in minimizing the degree of hypothermia experienced in cats anesthetized with halothane for 90 minutes. Deep rectal temperature was an accurate reflection of esophageal temperature in these cats. Clinical Relevance-Forced air warming blankets may prove successful in minimizing anesthetic-induced hypothermia in cats. (C)Copyright 1999 by The American College of Veterinary Surgeons.