Forced-air warming effectively prevents midazolam-induced core hypothermia in volunteers

Midazolam is a commonly used sedative and anaesthetic adjuvant and the agent is known to decrease core temperature by core-to-periphery redistribution of heat. We tested the hypothesis that forced-air warming could effectively prevent midazolam-induced hypothermia.

Six healthy male volunteers were studied over 3 days. On the first day, the volunteers were alert during a 30 min control period with forced-air warming. On the second day, after the volunteers were vasoconstricted, 75 microg kg(-1) midazolam was injected intramuscularly and they were covered with a cotton blanket. On the third day, after the volunteers were vasoconstricted, 75 microg kg(-1) midazolam was again administered and they were given forced-air warming. Tympanic temperature was measured as the core temperature. Four adhesive skin-surface probes with thermocouples were fixed on the chest, upper right arm, lateral calf and thigh, and both mean skin and body temperatures were calculated. Fingertip perfusion was evaluated using forearm minus fingertip and calf minus toe skin-surface temperature gradients. Thirty minutes after the intramuscular injection of midazolam, the level of sedation in volunteers was measured by a blinded observer according to the alertness/sedation scale.

Core temperature significantly decreased by midazolam premedication in a time-dependent manner. Although forced-air warming did not prevent the midazolam-induced transient decrease in core temperature, it increased the temperature to the control level thereafter.

We conclude that forced-air warming can effectively prevent midazolam-induced redistribution hypothermia.