Whole-body temperature gradients under surface, perfusion, and combined surface/perfusion hypothermia

Abstract Using various methods of hypothermia and halothane-diethyl ether azeotrope anesthesia whole-body temperature gradients were evaluated in 20 adult mongrel dogs. Simultaneous measurements were taken of brain, rectal, esophageal, pharyngeal, liver, jugular vein, shoulder muscle, thigh muscle, and subcutaneous temperatures during (i) surface, (ii) perfusion (slow and rapid cooling), and (iii) combined surface/perfusion methods of hypothermia. Throughout cooling and rewarming core temperature gradients averaged 1.2 °C and during circulatory arrest core temperatures decreased an average of 0.3 °C under pure surface hypothermia. Animals, thermoregulated by extracorporeal methods only, developed larger core temperature gradients during cooling and a significant increase (average = 3.1 °C) was noted in core temperatures during circulatory arrest. This pattern was particularly pronounced during rapid perfusion cooling. Hypothermia induction by combined surface/perfusion, in contrast to pure perfusion methods, resulted in smaller gradients without remarkable increase in core temperature (average = 1.3 °C) during the arrest period. These findings when correlated with the shorter total operating time and ease of operative management and resuscitation lead us to the conclusion that combined surface/ perfusion hypothermia techniques have certain advantages over either pure surface or pure perfusion techniques alone.