D-tubocurarine requirement during hypothermia.

The effect of hypothermia on the action of d-tubocurarine (d-TC) was studied under carefully controlled experimental conditions. It was found that with computer controlled infusion, 60% less d-TC was required to sustain 75% muscle paralysis in cats, during steady-state, in vivo, when the temperature was changed from 37 degrees C to 30 degrees C. The corresponding relaxant consumption rates were 0.136 +/- 0.025 and 0.055 +/- 0.012 mg/kg/1/2 hr respectively. When there was no temperature change the maintenance dosage of d-TC remained constant for up to four hours denoting the equilibrium phase of the relaxant kinetics. Temperature transitions introduced dynamic changes in these kinetics and altered the constancy of the maintenance dosage.