Intra–Cardiopulmonary Resuscitation Hypothermia With and Without Volume Loading in an Ischemic Model of Cardiac Arrest

Abstract

Background— We investigated the effects of intra–cardiopulmonary resuscitation (CPR) hypothermia with and without volume loading on return to spontaneous circulation and infarction size in an ischemic model of cardiac arrest. Methods and Results— Using a distal left anterior descending artery occlusion model of cardiac arrest followed by resuscitation with a total of 120 minutes of occlusion and 90 minutes of reperfusion, we randomized 46 pigs into 5 groups and used myocardial staining to define area at risk and myocardial necrosis. Group A had no intervention. Immediately after return of spontaneous circulation, group B received surface cooling with cooling blankets and ice. Group C received intra-CPR 680±23 mL of 28°C 0.9% normal saline via a central venous catheter. Group D received intra-CPR 673±26 mL of 4°C normal saline followed by surface cooling after return of spontaneous circulation. Group E received intra-CPR and hypothermia after return of spontaneous circulation with an endovascular therapeutic hypothermia system placed in the right atrium and set at a target of 32°C. Intra-CPR volume loading with room temperature (group C) or iced saline (group D) significantly ( P <0.05) decreased coronary perfusion pressure (group C, 12.8±4.78 mm Hg; group D, 14.6±9.9 mm Hg) compared with groups A, B, and E (20.6±8.2, 20.1±7.8, and 21.3±12.4 mm Hg). Return of spontaneous circulation was significantly improved in group E (9 of 9) compared with groups A plus B and C (10 of 18 and 1 of 8). The percent infarction to the area at risk was significantly reduced with intra-CPR hypothermia in groups D (24.3±4.2%) and E (4±3.4%) compared with groups A (72±5.1%) and B (67.3±4.2%). Conclusions— Intra-CPR hypothermia significantly reduces myocardial infarction size. Elimination of volume loading further improves outcomes.