Abstract 12140: Effect of Hypothermia on the Peripheral and Cerebral Microcirculation in a Rat Model of Cardiac Arrest

Abstract

Introduction: Therapeutic hypothermia improves outcomes after cardiac arrest (CA) and is a standard therapy for comatose patients after successful initial resuscitation. Post-resuscitation functional vital organ recovery is largely dependent on microcirculatory function. The effects of hypothermia on the peripheral and cerebral microcirculation following CA are not fully understood. Hypothesis: Hypothermia reduces the peripheral microcirculatory flow. However, the microcirculatory flow of cerebral cortex is preserved during hypothermia in a rat model of CPR. Methods: Twenty-one male Sprague-Dawley rats were randomized into three groups: hypothermic (HT, n=8), normothermic (NT, n=8) or sham-operated group (SO, n=5). Ventricular fibrillation was induced electrically and untreated for 8 mins, followed by 8 mins of precordial compressions and mechanical ventilations. The core temperature was reduced to 33±0.2°C at 5 mins following successful resuscitation and maintained for 8 hrs in the HT group. Normothermic animals were maintained at 37±0.2°C for 8 hrs. Sublingual and cerebral cortex microcirculation was measured by a sidestream dark-field imaging device at baseline, 1, 2, 3, 4, 6 and 8 hrs post-resuscitation. Results: All animals were resuscitated successfully. The sublingual microcirculatory flow index (MFI) was decreased significantly compared to the cerebral cortex MFI in the HT group following resuscitation (P< 0.05) (Figure 1). However, sublingual and cerebral microcirculation were impaired equally in the NT group after resuscitation.(Figure 2) Conclusions: A similar reduction in both sublingual and cerebral cortex microcirculatory flow was observed following resuscitation under conditions of normothermia. Hypothermia preserved the cerebral cortex microcirculation, but not the peripheral microcirculation, after resuscitation.