Rapid induction of hypothermia with a small volume aortic flush during cardiac arrest in pigs

PurposeThe induction of deep cerebral hypothermia (15°C) via large-volume cold (4°C) saline aortic flush during cardiac arrest and resuscitation with cardiopulmonary bypass improves neurologic outcome in pigs. We hypothesized that induction of mild cerebral hypothermia (33°C) via smaller volume and resuscitation without bypass will improve survival and neurologic outcome after 15 minutes of cardiac arrest as compared with conventional resuscitation attempts.Basic ProceduresTwenty-four pigs (29-38 kg) underwent ventricular fibrillation cardiac arrest for 15 minutes. Conventional resuscitation (n = 8) was compared with hypothermic (4°C, n = 8) and normothermic (38.5°C, n = 8) aortic flush (30 mL/kg) at the beginning of resuscitation efforts, with defibrillation attempts 2 minutes later. Outcomes after 9 days were compared.Main FindingsIn the hypothermic flush group, brain temperature decreased from 38.3°C ± 0.5°C to 33°C ± 0.5°C within 277 ± 112 seconds. We observed considerably higher mean coronary perfusion pressures in the normothermic and hypothermic flush groups (hypothermic vs conventional, P = .023; normothermic vs conventional, P = .041). Three animals of each flush group, compared with none of the conventional group, achieved restoration of spontaneous circulation (P = .2); and 3 pigs of the hypothermic flush group and 2 pigs of the normothermic flush group survived to 9 days without differences in neurologic outcome.Principal ConclusionA smaller volume, cold saline aortic flush during prolonged cardiac arrest rapidly induces mild cerebral hypothermia to 33°C and improves coronary perfusion pressure but does not result in a significant improvement in outcome as compared with conventional resuscitation attempts.