Long-term mild hypothermia with extracorporeal lung and heart assist improves survival from prolonged cardiac arrest in dogs

Abstract

Background and purpose: although normothermic extracorporeal lung and heart assist (ECLHA) improves cardiac outcomes, patients can not benefit from hypothermia-mediated brain protection. The present study evaluated the effects of long-term ECLHA with mild to moderate hypothermia (33°C) in a canine model of prolonged cardiac arrest. Methods: 15 dogs were assigned to either the hypothermic (seven dogs, 33°C) or normothermic group (eight dogs, 37.5°C). All dogs were induced to normothermic ventricular fibrillation (VF) for 15 min, followed by 24 h of ECLHA and 72 h of intensive care. The hypothermia group maintained core (pulmonary artery) temperature at 33°C for 20 h starting from resuscitation, then were rewarmed by 28 h. Outcome evaluations included: (1) mortality; (2) catecholamine dose; (3) time to extubation; (4) necrotic myocardial mass (g); and (5) neurological deficits score (NDS). Results: in the normothermic group five dogs died of cardiogenic shock and one dog succumbed to poor oxygenation. The two surviving dogs remained comatose (NDS 60.5±4.9%) with necrotic myocardial mass of 14.5±3.5 g. In the hypothermic group, one dog died from pulmonary dysfunction, the other six dogs survived. The surviving dogs showed brain damage (29.8±2.5%), but there was evidence of some brain-protective effect. The mass of necrotic myocardium was 4.2±1.3 g in the hypothermic group or 3.4 times smaller than in the normothermic group. The survival rate was significantly higher in the hypothermic than in the normothermic group ( P<0.05). The catecholamine requirement was also lower in the hypothermic than in the normothermic dogs ( P<0.05). Conclusions: Long-term mild to moderate hypothermia with ECLHA induced immediately after cardiac arrest improved survival as well as cerebral and cardiac outcomes.