To investigate whether hypothermia could be induced pharmacologically after resuscitation with the cannabinoid CB1/CB2 receptor agonist in a rat model and its effects on outcomes of cardiopulmonary resuscitation.
Prospective, randomized, placebo-controlled experimental study.
University-affiliated animal research laboratory.
Ten healthy male Sprague-Dawley rats.
Ventricular fibrillation was induced and untreated for 6 mins. Defibrillation was attempted after 8 mins of cardiopulmonary resuscitation. Thirty minutes after resuscitation, animals were randomized to receive either WIN55, 212-2 (1.0 mg/kg/hr) or vehicle placebo (1.4 mL/kg/hr) for 6 hrs. Before infusion, the temperature was maintained at 37°C in all the animals with the help of a heating lamp. The same temperature environment was maintained for both groups after infusion.
Measurements and Main Results:
Hemodynamic measurements and cardiac output, ejection fraction, and myocardial performance index were measured at baseline and hourly for 6 hrs after resuscitation. Survival time up to 72 hrs was observed.
Blood temperature decreased progressively after infusion of WIN55, 212-2 from 37°C to 34°C 4 hrs after resuscitation. There was no significant change in blood temperature after 6 hrs of placebo infusion of the same volume and same infusate temperature. Significantly better postresuscitation myocardial function and longer durations of survival were observed in WIN55, 212-2-treated animals.
The selective cannabinoid agonist, WIN55, 212-2, produced a significant reduction in blood temperature and improved postresuscitation myocardial functions and survival after cardiopulmonary resuscitation. The study results may provide a further option for early and effective induction of therapeutic hypothermia in settings of cardiopulmonary resuscitation.