Intra-cardiopulmonary resuscitation hypothermia with and without volume loading in an ischemic model of cardiac arrest

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.