Canadian journal of physiology and pharmacology
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Can. J. Physiol. Pharmacol. · Oct 2006
Effects of sympathetic stimulation during cooling on hypothermic as well as posthypothermic hemodynamic function.
This experimental study was performed to explore hemodynamic effects of a moderate dose epinephrine (Epi) during hypothermia and to test the hypothesis whether sympathetic stimulation during cooling affects myocardial function following rewarming. Two groups of male Wistar rats (each, n=7) were cooled to 15 degrees C, maintained at this temperature for 1 h, and then rewarmed. Group 1 received 1 microg/min Epi, i.v., for 1 h during cooling to 28 degrees C, a dose known to elevate cardiac output (CO) by approximately 25% at 37 degrees C. ⋯ Thus, before cooling, continuous Epi infusion predominantly stimulates myocardial mechanical function, materialized as elevation of CO, left ventricular systolic pressure, and maximum rate of left ventricle pressure rise. Cooling, on the other hand, apparently eradicates central hemodynamic effects of Epi and during stable hypothermia, elevation of peripheral vascular vasopressor effects seem to take over. In contrast to temperature-matched, non-Epi stimulated control rats, a significant depression of myocardial mechanical function occurs during rewarming following a moderate sympathetic stimulus during initial cooling.