IM MIDAZOLAM AS PREMEDICATION PRODUCES A CONCENTRATION-DEPENDENT DECREASE IN-CORE TEMPERATURE IN MALE-VOLUNTEERS

We tested the hypothesis that premedication with i.m. midazolam decrea ses core temperature dose-dependently. We studied six male volunteers, in random order, on 3 days: (1) no midazolam administration (control day), (2) midazolam 0.025 mg kg(-1) i.m., (3) midazolam 0.075 mg kg(-1 ) i.m. On the first day, subjects were maintained alert during a 30-mi n control period. On the second and third days, midazolam 0.025 or 0.0 75 mg kg(-1) was administered i.m. Core temperatures were measured at the right tympanic membrane. Four adhesive skin surface probes were fi xed on the chest, upper right arm, lateral calf and thigh. Finger tip perfusion was evaluated using forearm minus fingertip and calf minus t oe, skin surface temperature gradients. Thirty minutes after midazolam i.m., the lever of sedation in the volunteers was assessed. Periphera l venous blood was obtained immediately after the assessment of the le vel of sedation. Tympanic membrane temperatures after administration o f midazolam 0.075 mg kg(-1) i.m. were significantly lower than those o n the control and midazolam 0.025 mg kg(-1) i.m. days at 20 and 30 min . The decreases in tympanic membrane temperatures at 30 min after mida zolam i.m. became larger as the volunteers were more deeply sedated. i .m. midazolam produced a concentration-dependent decrease in tympanic membrane temperature at 30 min after midazolam 0.025 and 0.075 mg kg(- 1) i.m. We conclude that midazolam impaired tonic thermoregulatory vas oconstriction, allowing core-to-peripheral heat redistribution in a do se-dependent manner after i.m. administration.