The physiologic responses to epinephrine during cooling and after rewarming in vivoReport as inadecuate

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Critical Care

, 15:R225

First Online: 23 September 2011Received: 08 June 2011Revised: 12 August 2011Accepted: 23 September 2011


IntroductionThe purpose of our study was to determine whether hypothermia has any effects on physiological hemodynamic responses to epinephrine Epi, and whether rewarming reverses these effects.

MethodsSprague-Dawley rats were instrumented to measure mean arterial pressure MAP, and left ventricular LV pressure-volume changes were recorded by using a Millar pressure-volume conductance catheter. Core temperature was reduced from 37°C to 28°C and returned to 37°C by using both internal and external heat exchangers. Two groups of rats were infused with either saline n = 7, or Epi 0.125 μg-min continuously n = 7. At 33°C, 30°C, and 28°C, the Epi infusion was temporarily increased from 0.125 to 1.25 μg-min.

ResultsBefore cooling, Epi infusion in both groups resulted in a significant, dose-dependent increase in heart rate HR, stroke volume SV, cardiac output CO, LV dP-dtmax maximum derivative of systolic pressure over time, but only Epi infusion at 1.25 μg-min caused elevation of MAP. During cooling to 30°C, Epi infusion at 0.125 μg-min caused a significant elevation of central hemodynamic variables, whereas MAP remained unchanged. In contrast, Epi infusions at 1.25 μg-min caused a significant elevation of MAP during cooling to 28°C but no increases in central hemodynamics. After rewarming, all hemodynamic variables returned to baseline in both groups, but only the saline-treated animals displayed the prehypothermic hemodynamic dose responses to Epi infusions.

ConclusionsThis study shows that hypothermia causes a change in the physiological hemodynamic response to Epi, which is not reversed by rewarming.

AbbreviationsCOcardiac output

dP-dtmaxmaximum derivative of systolic pressure over time

EDPend-diastolic pressure

EDVend-diastolic volume

ESPend-systolic pressure


ESVend-systolic volume

HRheart rate

LVleft ventricular

MAPmean arterial pressure

SVstroke volume

SWstroke work

Tauisovolumetric relaxation time.

Electronic supplementary materialThe online version of this article doi:10.1186-cc10465 contains supplementary material, which is available to authorized users.

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Author: Torkjel Tveita - Gary C Sieck


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