Abstract P110: Exploratory Study on Mechanism by Which Hypothermia Improves Outcomes of Cardiopulmonary Resuscitation
Introduction: In an earlier report, our group demonstrated that when head cooling was started during CPR, outcomes were improved. We had also reported in a series of studies the adverse effects on ultimate outcomes of adrenergic amines, both á1 and âadrenergic agonists and improved outcomes withá1 and âadrenergic blockades. We therefore hypothesized that the benefits of rapid head cooling may at least in part relate to reduced adrenergic stimulation. In a small exploratory study, we therefore measured endogenous plasma concentration of norepinephrine.
Methods: Pilot studies were conducted in 7 domestic male pigs weighing 40±5 kg. After 15 minutes of untreated ventricular fibrillation, in 4 animals head cooling was induced with a Rhino Chill device coincident with start of CPR. An additional 3 animals served as identically treated controls without hypothermia. CPR was continued for 5 minutes in both group prior to defibrillation. Endogenous plasma norepinephrine levels were measured at baseline and 5 minutes after start of CPR.
Results: None of the control animals were successfully resuscitated, in contrast to 3 of 4 brain cooled animals. Jugular vein temperature was reduced from 38.0°C to 37.0°C in brain cooled animals (P<0.001). Endogenous norepinephrine levels were greatly increased in comparing to baseline levels and was significantly less in brain cooled animals (153 vs 381 μg/L, P<0.05)
Conclusions: The mechanism by which rapid head cooling improves outcome of resuscitation may, at least in part, relate to inhibition of the adverse effects of endogenous adrenergic stimulation.