Comparison of the Durations of Mild Therapeutic Hypothermia on Outcome Following Cardiopulmonary Resuscitation in the Rat
Background—Current studies demonstrated that applying therapeutic hypothermia for 12 to 24 hours following resuscitation from cardiac arrest improves the outcomes of cardiopulmonary resuscitation (CPR). The present study investigated whether a shorter duration of therapeutic hypothermia induced quickly and early following resuscitation would provide an equal improvement of the outcomes of CPR.
Methods and Results—Ventricular fibrillation was induced and untreated for 8 minutes in twenty four male Sprague-Dawley rats. Defibrillation was attempted after 8 minutes of CPR. Seven minutes after resuscitation, animals were randomized into 4 groups (n = 6 each): normothermic, hypothermic-2hrs, hypothermic-5hrs, and hypothermic-8hrs. Animals in the hypothermic groups received rapid cooling which was started 7 minutes following ROSC and maintained at 33±0.5°C for 2, 5, or 8 hours. Normothermic animals were maintained at 37±0.2°C. All animals were anesthetized and ventilated for 8 hours after resuscitation. Blood temperature was significantly decreased in the hypothermic groups. Post-resuscitation myocardial function, neurological deficit scores and 72 hour survival were significantly better in animals treated with hypothermia regardless of the duration of cooling. However, significantly better post-resuscitation tissue microcirculation, myocardial ejection fraction and neurological deficit scores were observed in the hypothermic-2hrs animals.
Conclusions—In a rat model of CPR, a shorter duration of mild hypothermia induced rapidly and early following ROSC improved post-resuscitation microcirculation, myocardial and cerebral functions and survival equally or better than prolonged duration of hypothermia following resuscitation.
- Received August 15, 2011.
- Accepted October 27, 2011.
- Copyright © 2011, American Heart Association, Inc. All rights reserved. Unauthorized use prohibited