Hypothermia reduces resuscitation fluid volumes required to maintain blood pressure in a rat hemorrhagic shock model

Abstract

To examine the hypothesis that resuscitative hypothermia would (1) reduce fluid requirements and reactive oxygen species production during a period of resuscitation and (2) improve survival after hemorrhagic shock (HS) in rats. Sixteen rats underwent an HS phase (phase I: 0-75 minutes), with pressure-controlled HS at a mean arterial pressure of 30 mm Hg ± 5 mm Hg; a resuscitation phase (phase II: 75-150 minutes), with fluid resuscitation to maintain mean arterial pressure ≥75 mm Hg; and an observation phase (phase III: from 150 minutes to 72 hours). During phase II, eight rats were randomized into a normothermia group (group 1: 38°C) or a hypothermia group (group 2: 34°C). Fluid requirements during phase II and survival at 72 hours were compared between groups. Plasma levels of Vitamin E and %coenzyme Q9 (%CoQ9) were also assessed. The fluid requirement during resuscitation in phase II was 8.2 ± 1.4 mL/100 g in group 1 versus 2.1 mL/100 g ± 0.7 mL/100 g in group 2 (p < 0.01). Vitamin E level decreased to 10.8 μmol/L ± 1.8 μmol/L during HS in all rats. After resuscitation, it was restored to a baseline level of 15.9 μmol/L ± 3.1 μmol/L in group 2 but remained at 10.2 μmol/L ± 0.8 μmol/L in group 1 (p < 0.05). %CoQ9 did not differ significantly between the groups. At 72 hours, six of eight rats in group 1, and all rats in group 2 survived (NS). In a rat HS model, hypothermia during resuscitation from HS reduces resuscitation fluid volume required to maintain blood pressure and restores Vitamin E to the baseline level, and appears to have no adverse impact on long survival after HS.