Propofol in low doses causes redistribution of body heat in male volunteers.

Abstract

Cardiovascular and mental stress in dental patients with phobias about dentistry may be reduced by propofol sedation. We tested the hypothesis that even low doses of propofol may have effects on body temperatures in male volunteers. Six healthy male volunteers were given propofol over 28 min with the following infusion rates: 8 mg kg(-1) h(-1) for the first 3 min, 4 mg kg(-1) h(-1) for the next 10 min, and 2 mg kg(-1) h(-1) for the final 15 min. Body temperatures were measured at five locations: tympanic membrane, forehead, forearm, dorsum of the hand and fingertip. Thermoregulatory vasoconstriction was evaluated using the forearm minus fingertip temperature gradient. Tympanic membrane and forehead temperatures began to decrease at 10 and 20 min, respectively, after the start of the propofol infusion, and reached a minimum at 30 min (tympanic -0.5 +/- 0.2 degrees C) and 40 min (forehead -0.6 +/- 0.2 degrees C), respectively. Peripheral skin temperatures showed an increase between 10 and 30 min in the forearm and fingertip and between 20 and 30 min in the dorsum of the hand. After 30 min, a decrease in peripheral skin temperatures was observed. The forearm minus fingertip temperature gradient changed from negative to positive after 40 min, and increased continuously thereafter (baseline -0.3 +/- 0.4 degrees C, 90 min: 6.5 +/- 1.6 degrees C). A low dose of propofol impairs tonic thermoregulatory vasoconstriction and induces heat redistribution from the core to the periphery.