Study Objective: To test the hypothesis that core temperature is well prese
rved when atropine and midazolam are combined.
Design: Randomized, blinded study.
Setting: Department of Anesthesia, Yamanashi Medical University.
Patients: 40 elderly, ASA physical status I and II patients (aged more than
Interventions: Patients were randomly assigned (n = 10 per group) to premed
ication 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 p
remedication was given on the ward at approximately 8:30 AM, approximate to
30 minutes before induction of anesthesia.
Measurements and Main Results: Core 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 usin
g forearm minus fingertip and calf minus toe, skin-surface temperature grad
ients. Temperatures were evaluated at the time of premedication and 30 minu
tes later, just before induction of anesthesia. Core temperature remained n
early constant in the control patients (0.1 +/- 0.2 degreesC; mean +/- SD),
whereas it decreased significantly in the patients given midazolam alone (
-0.3 +/- 0.1 degreesC). Atropine alone increased core temperature (0.3 +/-
0.2 degreesC), although the increase was not statistically significant. The
combination of midazolam and atropine attenuated the hypothermia induced b
y midazolam alone (0.0 +/- 0.2 degreesC). Initial skin-temperature gradient
s exceeded 0 degreesC in all groups, indicating that the patients were vaso
constricted. The gradients were unchanged by premedication with saline or a
tropine. Midazolam significantly decreased the gradient (-1.8 +/- 1.1 C), a
s did the combination of midazolam and atropine (-1.4 +/- 0.9 degreesC).
Conclusions: The thermoregulatory effects of benzodiazepine receptor agonis
t and cholinergic inhibitors oppose each other, and the combination leaves
core temperature unchanged. 2001 by Elsevier Science Inc.