Therapeutic hypothermia limited to the resuscitation period does not prolong survival after severe hemorrhagic shock in rats.

OBJECTIVE

Controlled hypothermia induced during hemorrhagic shock (HS) has been shown previously to improve survival in HS rat outcome models. We hypothesized that hypothermia (34 degrees C) induced immediately with reperfusion would also improve survival.

METHODS

Twenty-four rats were lightly anesthetized with halothane and maintained spontaneous breathing. The rats underwent: an HS phase I of 75 min, with an initial blood withdrawal of 2.5 mL/100 g over 15 min, followed by either additional blood withdrawal or re-infusion in order to maintain a mean arterial pressure (MAP) of 30 mmHg over 60 min; a resuscitation phase II of 60 min with return of shed blood and infusion of lactated Ringer's solution to maintain a MAP of 75 mmHg; and an observation phase III without anesthesia for 72 h. Five minutes before the start of phase II, 12 rats were randomized into either a normothermia (38 degrees C) group or hypothermia (34 degrees C) group. The rectal temperature in each group was carefully maintained during the 60-min period of phase II. Survival at 72 h, as well as gut damage were assessed.

RESULTS

All 24 rats survived beyond phases I and II. At 72 h, 8 of 12 rats survived in the hypothermia group, while and 6 of 12 survived in the normothermia group (p=0.64). Intestines of the 72 h survivors were macroscopically normal. In rats that died during phase III, total gut scores did not differ statistically between the groups (1.2+/-0.6 versus 1.0+/-0.9).

CONCLUSION

Brief resuscitative hypothermia of 60 min duration induced immediately with reperfusion after HS did not improve survival in this model.