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

Background and purpose: although normothermic extracorporeal lung and heart assist (ECLHA) improves cardiac outcomes, patients can not benefit from hy pothermia-mediated brain protection. The present study evaluated the effect s of long-term ECLHA with mild to moderate hypothermia (33 degreesC) in a c anine model of prolonged cardiac arrest. Methods: 15 dogs were assigned to either the hypothermic (seven dogs, 33 degreesC) or normothermic group (eig ht dogs, 37.5 degreesC). All dogs were induced to normothermic ventricular fibrillation (VF) for 15 min, followed by 24 h of ECLHA and 72 h of intensi ve care. The hypothermia group maintained core (pulmonary artery) temperatu re at 33 degreesC for 20 h starting from resuscitation, then were rewarmed by 28 h. Outcome evaluations included: (1) mortality; (2) catecholamine dos e; (3) time to extubation: (4) necrotic myocardial mass (g); and (5) neurol ogical deficits score (NDS). Results: in the normothermic group five dogs d ied of cardiogenic shock and one dog succumbed to poor oxygenation. The two surviving dogs remained comatose (NDS 60.5 +/- 4.9%) with necrotic myocard ial mass of 14.5 +/- 3.5 g. In the hypothermic group. one dog died from pul monary dysfunction, the other six dogs survived. The surviving dogs showed brain damage (29.8 +/- 2.5%), but there was evidence of some brain-protecti ve effect. The mass of necrotic myocardium was 4.2 +/- 1.3 g in the hypothe rmic group or 3.4 times smaller than in the normothermic group. The surviva l rate was significantly higher in the hypothermic than in the normothermic group (P < 0.05). The catecholamine requirement was also lower in the hypo thermic than in the normothermic dogs (P ( 0.05). Conclusions: Long-term mi ld to moderate hypothermia with ECLHA induced immediately after cardiac arr est improved survival as well as cerebral and cardiac outcomes. (C) 2001 El sevier Science Ireland Ltd. All rights reserved.