Should normothermia be restored and maintained during resuscitation after trauma and hemorrhage?

Background: Although hypothermia often occurs after trauma and has protecti ve effects during ischemia and organ preservation, it remains unknown wheth er maintenance of hypothermia or restoring the body temperature to normothe rmia during resuscitation has any deleterious or beneficial effects on hear t performance and organ blood flow after trauma-hemorrhage, Methods: Male rats underwent laparotomy (i.e., induced trauma) and were exs anguinated to and maintained at a mean arterial pressure of 40 mm Hg until 40% of the maximum shed volume was returned in the form of Ringer's lactate . Body temperature decreased from approximately 36.5 degrees C to below 32 degrees C, The animals were then resuscitated with four times the volume of maximal bleedout with Ringer's lactate. In one group, body temperature was rewarmed to 37 degrees C during resuscitation, In another group, body temp erature was maintained at hypothermia (32 degrees C) for 3 hours after resu scitation, In an additional group, the body temperature was kept at 37 degr ees C during hemorrhage as well as during resuscitation. Left ventricle per formance parameters such as maximal rate of left ventricular pressure incre ase and decrease (+/-dP/dt(max)) were measured up to 4 hours. Cardiac outpu t and regional blood flow were determined by radioactive microspheres at 4 hours after the completion of resuscitation, Results: The maintenance of normothermia during hemorrhage or prolonged hyp othermia after resuscitation depressed the left ventricular performance par ameters, cardiac output, and regional blood flow in various organs. Rewarmi ng the body to normothermia during resuscitation, however, significantly in creased heart performance, cardiac output (from hypothermia 16.2 +/- 1.4 to 22.3 +/- 1.4 mL/min per 100 g body weight,p < 0.05) and total hepatic bloo d flow (from hypothermia 117.5 +/- 5.3 to 166.0 +/- 9.3 mL/min per 100 g ti ssue, p < .05), Conclusion: Our data indicate that restoration of normothermia during resus citation improves cardiac function and hepatic blood flow compared with hyp othermia.