Abstract 315: Both Systemic and Cerebral Microcirculation Are Reduced During Hypothermia in a Porcine Model

Abstract

Introduction: Mild hypothermia improves neurological outcomes after cardiac arrest. However, systemic microcirculation is reduced with the reduction of body temperature. We investigated the changes of cerebral (CM) and sublingual microcirculation (SM) during hypothermia in a porcine model during spontaneous circulation and following successful cardiopulmonary resuscitation. Hypothesis: We hypothesized that during spontaneous circulation and following CPR, SM is reduced with the progress of hypothermia. However, CM is preserved in the range of mild hypothermia. Methods: Ten domestic pigs weighing 34±1kg were randomized into spontaneous circulation control or CPR groups. The cerebral cortices were exposed for microcirculation measurement. In CPR group, ventricular fibrillation (VF) was induced and untreated for 5 mins. Defibrillation of 150J was attempted after 5 mins of CPR. Hypothermia was initiated after completion of animal preparation in control group and immediately following successful resuscitation in CPR group. The blood temperature was reduced from 37°C to 35°C, 33°C and 28°C with a cooling blanket. SM and CM was measured at each temperature point with the orthogonal polarization spectral imaging technique. Results: Microcirculatory blood flow index and perfused microvessel density of both SM and CM decreased with the progress of hypothermia in both groups. There was no statistical difference between the two groups. (Table) Conclusion: CM is reduced with the reduction of body temperature during spontaneous circulation and following CPR. The relationship between reduced CM during hypothermia and improved neurological outcomes following hypothermia remains to be investigated.