Sodium Nitroprusside Enhanced CPR and intra-CPR Hypothermia

Abstract

Objective : Therapeutic Hypothermia (TH) is thought to improve neurologically intact survival when applied after Return of Spontaneous Circulation (ROSC) is achieved in patients who suffer a cardiac arrest. Intra-CPR cooling may accelerate the time to reach TH and thus enhance its neurological benefit. Sodium Nitroprusside Enhanced Cardiopulmonary Resuscitation (SNPeCPR) has been shown to accelerate intra-CPR cooling compared to standard CPR. The aim of this study is to assess which method of therapeutic hypothermia is the most efficient in decreasing brain temperature during SNPeCPR. Methods: This study included 24 intubated and anesthetized swine. After induction of Ventricular Fibrillation (VF), animals were randomized to one of the following groups: 500cc cold saline infusion (group A), 500cc cold saline infusion plus surface cooling with ice packs (group B), surface cooling only (group C) or control/no cooling method applied (group D). After 10 minutes of VF, CPR was initiated. One minute after the initiation of CPR, the randomized intervention was initiated and abdominal binding was applied. SNP (2 mg) was administered at minutes 1, 4 and 8. Animals were defibrillated at minute10. Results: Within 4 minutes of CPR, animals that received intravenous cold saline (Group A and Group B) had decreased their brain temperature by 0.5 °C lower compared to the groups that had not (Group C and Group D). Group B presented a superior heat exchange rate from blood to skin compared to group A. Conclusion : It was observed that cold saline infusion during SNPeCPR accelerates cooling of the brain. Ice packs work synergistically by optimizing heat transfer from the blood to the skin. Further studies will assess the potential neurologic benefit of the combination of SNPeCPR with intra-CPR infusion of cold saline.