Evaluation of cerebral metabolism by ¹H-magnetic resonance spectroscopy for 4°C saline-induced therapeutic hypothermia in pig model of cardiac arrest.

BACKGROUND: Previous studies have shown that therapeutic hypothermia could improve neurologic recovery when induced after cardiac arrest, but dynamic changes in cerebral metabolism have not been studied at low temperature. In this study, we aim to evaluate hypothermia-induced changes in pigs' cerebral metabolism by (1)H-magnetic resonance spectroscopy (¹H-MRS).
MATERIAL AND METHODS: Ten anesthetized Landrace (25-30 kg) pigs were randomized into 2 groups and subjected to 4 minutes of ventricular fibrillation, followed by cardiopulmonary resuscitation. The hypothermic group was given an infusion of 30 mL/kg of 4°C normal saline (NS) at an infusion rate of 1.33 mL/kg per minute starting after restoration of spontaneous circulation (ROSC), then 10 mL/kg per hour for 4 hours. The control group received the same infusion of room temperature NS. Core temperature and hemodynamic variables were monitored at baseline and repeatedly for 240 minutes after ROSC. The ¹H-MRS scans were obtained at baseline, 1 hour, and 3 hours after successful ROSC to observe the dynamic changes of cerebral metabolism at different temperatures.
RESULTS: The mean reduction of temperature was 1.5°C ± 0.4°C in the hypothermic group. There was no difference in hemodynamic variables between groups. ¹H-MRS detected statistically significant (P < .01) changes in cerebral metabolism between the control and hypothermia groups (P < .01).
CONCLUSIONS: Infusion of 4°C NS can effectively reduce cerebral metabolism after successful cardiopulmonary resuscitation and have a protective effect on the recovery of neurologic function. The ¹H-MRS technology can be used as a powerful tool to evaluate interventions in the treatment of cardiopulmonary resuscitation.