Abstract 83: Effect of Therapeutic Hypothermia on Oxygenation Index in Rat Model of Cardiac Arrest

Abstract

Introduction: Therapeutic hypothermia improves the outcomes of cerebral function after resuscitation from cardiac arrest (CA). The effect of therapeutic hypothermia on post resuscitation pulmonary function, however, is less known. In the present study, we investigated the effect of therapeutic hypothermia on oxygenation index, a sensitive index of pulmonary function,in a rat model of cardiac arrest and resuscitation. Hypothesis: We hypothesize that during therapeutic mild hypothermia in a rat model of cardiac arrest, the pulmonary function following resuscitation is less impaired when compare to normothermia. Methods: Twenty-one male Sprague-Dawley rats were randomized into three groups: 1) control group (control, n=5): the normothermic rats only received anesthesia and the surgical procedure as the other groups without ventricular fibrillation (VF); 2) normothermia group (NT, n=7): the normothermic rats were subjected to induced VF for 8 mins followed by 8 mins of cardiopulmonary resuscitation (CPR); 3) Mild hypothermia group (HT, n=9): the rats were subjected to induced VF for 8 mins followed by 8 mins of CPR. Mild hypothermia of 33±0.5°C was started 5 mins after return of spontaneous circulation (ROSC) and maintained for 8 hrs. The oxygenation indexes were measured at baseline, 2, 4 or 8 hours after ROSC with a conventional blood gas analyzer (PHOX plus L; Nova Biomedical Corporation, Waltham, MA, USA). Results: Compared to the control group, the oxygenation indexes of both the NT and HT groups were significantly decreased at 2 hrs after ROSC. However, more significant reduction in oxygenation index was observed in the NT group (Figure). Conclusions: There is an early pulmonary dysfunction after successful resuscitation from cardiac arrest. Hypothermia reduces the impairment of pulmonary function.