Mild therapeutic hypothermia in cardiogenic shock syndrome*

Abstract

Mortality in patients with cardiogenic shock after out-of-hospital cardiac arrest remains high despite advances in resuscitation and early revascularization strategies. Recent studies suggest a reduced mortality in survivors of cardiac arrest subjected to mild therapeutic hypothermia, but the underlying mechanisms are not yet clear. Because positive hemodynamic effects of mild therapeutic hypothermia have been suggested, we aimed at testing the hypothesis that patients in cardiogenic shock might benefit from mild therapeutic hypothermia. Hemodynamic effects of mild therapeutic hypothermia in 20 consecutive patients admitted in cardiogenic shock after successful resuscitation from out-of-hospital cardiac arrest were investigated. A historic normothermic control group was matched (one-to-one) by means of a propensity score. Patients were cooled to 33°C for 24 hrs using an endovascular cooling device and hemodynamic variables were continuously recorded by means of pulse contour analysis. Cardiac performance was determined by echocardiography. Mild therapeutic hypothermia induced a significant decrease in heart rate from 74 to 64 beats per minute. Despite the reduction in heart rate, cardiac index remained unchanged under mild therapeutic hypothermia likely due to an increase in ejection fraction from 43 ± 4% to 55 ± 4%. Mean arterial pressure increased rapidly from 75 ± 2 mm Hg to 84 ± 3 mm Hg (p = .001) upon induction of hypothermia paralleled by an initial increase in systemic vascular resistance. Accordingly, patients with mild therapeutic hypothermia required lower cumulative doses of vasopressors and inotropes. We conclude that in cardiogenic shock mild therapeutic hypothermia provides circulatory support and an increase in systemic vascular resistance that leads to reduced vasopressor use and may result in lower oxygen consumption. These findings suggest that mild therapeutic hypothermia could be a therapeutic option in hemodynamically unstable patients independent of cardiac arrest and further randomized clinical studies are needed.