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

OBJECTIVE: To 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).
METHODS: Ventricular 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 (1)hydrogen proton magnetic resonance spectroscopy were acquired for each group at 6, 12, 24, and 72 hours after ROSC.
RESULTS: Compared 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.
CONCLUSIONS: Magnetic 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.