• T Matsukawa, M Ozaki, T Nishiyama, M Imamura, R Iwamoto, T Iijima, and T Kumazawa.
• Department of Anesthesia, Yamanashi Medical University, Yamanashi 49-3898, Japan. takashim@res.yamanashi-med.ac.jp
• J Clin Anesth. 2001 Nov 1; 13 (7): 504-8.

Study ObjectiveTo test the hypothesis that core temperature is well preserved when atropine and midazolam are combined.DesignRandomized, blinded study.SettingDepartment of Anesthesia, Yamanashi Medical University.Patients40 elderly, ASA physical status I and II patients (aged more than 60 years).InterventionsPatients were randomly assigned (n = 10 per group) to premedication with: 1) saline control; 2) midazolam 0.05 mg/kg; 3) atropine 0.01 mg/kg; and 4) midazolam 0.05 mg/kg combined with atropine 0.01 mg/kg. All premedication was given on the ward at approximately 8:30 am, approximately 30 minutes before induction of anesthesia.Measurements And Main ResultsCore temperatures were measured at the right tympanic membrane. Mean skin temperature was calculated as 0.3 x (T(chest) + T(arm)) + 0.2 x (T(thigh) + T(calf)). Fingertip perfusion was evaluated using forearm minus fingertip and calf minus toe, skin-surface temperature gradients. Temperatures were evaluated at the time of premedication and 30 minutes later, just before induction of anesthesia. Core temperature remained nearly constant in the control patients (0.1 +/- 0.2 degrees C; mean +/- SD), whereas it decreased significantly in the patients given midazolam alone (-0.3 +/- 0.1 degrees C). Atropine alone increased core temperature (0.3 +/- 0.2 degrees C), although the increase was not statistically significant. The combination of midazolam and atropine attenuated the hypothermia induced by midazolam alone (0.0 +/- 0.2 degrees C). Initial skin-temperature gradients exceeded 0 degrees C in all groups, indicating that the patients were vasoconstricted. The gradients were unchanged by premedication with saline or atropine. Midazolam significantly decreased the gradient (-1.8 +/- 1.1 degrees C), as did the combination of midazolam and atropine (-1.4 +/- 0.9 degrees C).ConclusionsThe thermoregulatory effects of benzodiazepine receptor agonist and cholinergic inhibitors oppose each other, and the combination leaves core temperature unchanged.

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