Effects of hypothermia on brain injury assessed by magnetic resonance imaging after cardiopulmonary resuscitation in a porcine model of cardiac arrest

Abstract

ObjectiveTo evaluate the effects of hypothermia on cerebral edema and metabolism, a porcine model of cardiac arrest was assessed by magnetic resonance imaging during the first 72 hours after restoration of spontaneous circulation (ROSC). MethodsVentricular fibrillation was induced in 33 pigs. After 8 minutes of untreated ventricular fibrillation, 30:2 cardiopulmonary resuscitation was performed. After ROSC, 30 survival animals were randomly divided into normothermia group (n = 15) and hypothermia group (n = 15). The hypothermia group immediately received endovascular cooling to regulate temperature to 33°C, which was maintained for 12 hours, followed by passive rewarming at 0.5°C/h to 37°C. Diffusion-weighted imaging and 1hydrogen proton magnetic resonance spectroscopy were acquired for each group at 6, 12, 24, and 72 hours after ROSC. ResultsCompared with the normothermia group, the hypothermia group exhibited a higher 72-hour survival (73.3% vs. 33.3%, P = .028) and a superior neurological deficit score (P = .031). Cerebral injury was found in both groups, but a lesser decrease in the apparent diffusion coefficient and N-acetyl aspartate/creatinine (P < .05) and a greater increase in choline/creatinine (P < .05) were found in the hypothermia group. ConclusionsMagnetic resonance imaging could effectively detect the dynamic trend of cerebral injury in a porcine model of cardiac arrest within the first 72 hours after ROSC. Hypothermia produced a protective effect on neurological function by reducing brain edema and formation of adverse metabolites.