Atropine prevents midazolam-induced core hypothermia in elderly patients.
OBJECTIVE
To test the hypothesis that core temperature is well preserved when atropine and midazolam are combined.


METHODS
Randomized, blinded study.


METHODS
Department of Anesthesia, Yamanashi Medical University.


METHODS
40 elderly, ASA physical status I and II patients (aged more than 60 years).


METHODS
Patients 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.


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 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).


CONCLUSIONS
The thermoregulatory effects of benzodiazepine receptor agonist and cholinergic inhibitors oppose each other, and the combination leaves core temperature unchanged.
Matsukawa
T
T
Department of Anesthesia, Yamanashi Medical University, Yamanashi 49-3898, Japan. takashim@res.yamanashi-med.ac.jp
Ozaki
M
M
Nishiyama
T
T
Imamura
M
M
Iwamoto
R
R
Iijima
T
T
Kumazawa
T
T
D000368:Aged; D001285:Atropine / Q000494:pharmacology*; D001833:Body Temperature Regulation / Q000187:drug effects; D005260:Female; D006439:Hemodynamics / Q000187:drug effects; D006801:Humans; D007035:Hypothermia / Q000139:chemically induced / Q000517:prevention & control*; D008297:Male; D008874:Midazolam / Q000009:adverse effects*; D011292:Premedication
D001285:Atropine; D008874:Midazolam