Effect of mild hypothermia on protecting heart function and improving survival rate after resuscitation of cardiac arrest in rats

Abstract

Objective To establish a rat model with cardiac arrest and resuscitation to study the role of mild hypothermia in protecting the post-resuscitation heart function and improving their survival outcomes. Methods Eighteen male SD rats were enrolled in the study and randomly divided into control group (normal temperature) and mild hypothermia group. Ventricular fibrillation model was induced electrically and the resuscitated rats were treated with mild hyperthermia. Heart function indices including ejection fraction and myocardial performance index were monitored by ultrasound at 1-4 hours after resuscitation. Neurological deficit score (NDS) was evaluated every 24 hours after resuscitation. The 24-hour and 72-hour survival rates were compared between two groups. Results All 18 rats were successfully resuscitated. There were no significant differences in success rate of ROSC, resuscitation time and success rate of first defibrillation. The heart function was worsened obviously in the rats of the control group at 1-4 hours after resuscitation, with left ventricular ejection fraction decreasing from baseline (74.9±2.2)% to (59.8±6.52)%, (50.4±4.4)%, (48.8±4.8)%, (47.8±6.1)%. While the left ventricular ejection fraction was changed from (73.9±2.5)% to (76.2±3.0)%, (75.1±3.5)%, (71.9±4.7)%, (64.1±3.1)%, with statistical difference between two groups. The myocardial performance index was increased from the baseline 0.6±0.1 to 1.1±0.1, 1.2±0.1, 1.3±0.2, 1.4±0.3 in the control group but increased from baseline 0.6±0.1 to 0.7±0.1, 0. 8±0.1, 0.8±0.1, 0.9±0.1, with worse results in the control group. The 72-hour survival animals in the mild hyperthermia group were significantly more than those in the control group. NDS at 24, 48 and 72 hours after resuscitation in the mild hyperthermia group was significantly lower than that in the control group. Conclusion In this model, mild hypothermia can protect the heart function and improve the neurological and survival outcomes of the resuscitated rats. Key words: Cardio-pulmonary resuscitation; Cardiac arrest; Mild hypothermia; Ventricular fibrillation