Internal Body Temperature Gradients During Anesthesia and Hypothermia and Effect of Vagotomy

¹ From the Laboratory of Chemical Pharmacology, National Heart Institute, National Institutes of Health, Bethesda, Maryland

During hypothermia rather large thermal gradients were noted between the rectum or colon and the heart. Heart blood temperature was assumed to be the most significant deep body temperature since the outflowing blood is the most important carrier of heat to or from tissues. The lower esophagus was found to be a good index of heart temperature in dogs during both surface and blood stream cooling and rewarming. The esophagus near the tracheal bifurcation was uniformly about 1° cooler, probably due to evaporation in the trachea below the endotracheal tube. In awake and anesthetized dogs the rectum averaged 0.5° warmer than the heart, but cooled and warmed more rapidly than the heart with surface cooling and warming, the mean gradients rising over 2°C. In most adults the rectum cooled and warmed more slowly than lower esophageal temperature, gradients of over 4° being noted. With blood stream cooling and rewarming, heart temperature led other deep temperatures in dogs. Vagotomy in dogs during surface cooling or rewarming resulted in rapid selective cooling or warming of an area of the colon between 10 and 22 cm from the anus. This was dependent on cooling of the abdominal skin and was not duplicated with atropine.