0354. Effects of sodium nitroprusside in addition to therapeutic hypothermia after experimental cardiac arrest

Methods We studied 8 anesthetized, invasively monitored and mechanically ventilated domestic pigs, randomized into two groups (n=4): TH without or with SNP. After 3 min of untreated ventricular fibrillation, cardiopulmonary resuscitation (CPR) was started in all animals and continued until return of spontaneous circulation (ROSC); defibrillation was performed 3 minutes after the start of CPR. Hypothermia (34±1°C) was induced at the start of CPR using a rapid IV infusion of 30 mL/kg cold saline for 60 min, trans-nasal evaporative cooling (Rhinochill, Benechill Inc, USA) and surface cooling with ice packs. Cooling was maintained for 6 hours, followed by controlled slow rewarming to baseline temperature with blankets. SNP +TH animals received 3 bolus injections of 1 mg of SNP after 2, 7 and 12 minutes of CPR. Brain temperature was measured with intraparenchymal probes (Licox CC1.SB, Integra, NeuroSciences Ltd., Hampshire, UK), blood brain flow by laser Doppler (blood laser Doppler [BLD], MNP100XP, Oxyflow, Oxford Optronix, Oxford, UK) and the lactate-pyruvate ratio (LPR) was measured hourly by microdialysis (CMA20, CMA, Sweden). After left craniectomy, the microvascular network of the frontal cortex was evaluated using sidestream dark-field videomicroscopy (Microscan, MicroVision Medical, Netherlands) at baseline (T0), 1 hour after cooling induction (T1), at the end of hypothermia (T2) and after rewarming (T3). The mean flow index (MFI) and the proportion of perfused cerebral