Thermoregulatory response in female patients during lower abdominal surgery in the head-down tilt position.

Abstract

The head-down tilt (HDT) position suppresses sympathetic nervous activity. We investigated the effect on thermoregulation of the HDT position during lower abdominal surgery under general anaesthesia. Tympanic membrane temperature was measured to assess core temperature, and forearm-fingertip and calf-toe temperature gradients were used to assess peripheral vasoconstriction in 30 female patients less than 60 years of age. During surgery in the HDT position (n = 10), the tympanic membrane temperature was similar to that of patients in the supine position (n = 10) (36.2 degrees C and 36.2 degrees C), but in patients operated in the HDT position and premedicated with an angiotensin converting enzyme inhibitor (5 mg of enalapril, n = 10) it was reduced (35.7 degrees C, P < 0.05). In both groups of patients operated in the HDT position, forearm and calf skin-surface temperature gradients were lower by 2.3 degrees C than those in patients operated in the supine position (P < 0.05). During lower abdominal surgery the head-down tilt position does not augment core hypothermia in spite of suppressed peripheral vasoconstriction, and the renin-angiotensin system may be of importance for thermoregulation.