Effect of moderate hypothermia in the treatment of canine hemorrhagic shock.

Abstract

This study evaluated a possible protective and therapeutic effect of moderate hypothermia in the treatment of severe hemorrhagic shock. A modified Wiggers shock preparation was used. Normothermic dogs (Group I, N = 6) were maintained at normal body temperature throughout hemorrhagic shock and resuscitation. In Group II, hypothermia was initiated after 15 minutes of hemorrhagic shock (N = 12) and maintained for 60 minutes after fluid resuscitation. Animals were then rewarmed with Group IIA (N = 7) receiving sodium bicarbonate to correct acidosis, while Group IIB (N = 5) did not; all dogs were studied for an additional 120 minutes. During shock heart rate was lower in both hypothermic groups (IIA and IIB) compared to normothermic dogs (85.0 +/- 3.9, 77.7 +/- 4.6 vs. 136.7 +/- 4.2, respectively, p less than 0.05), while +dP/dt (mmHg/s) remained stable in all dogs. Furthermore, pH was lower in the hypothermic (Groups IIA and IIB) compared to normothermic animals at this time period (Group IIA: 7.19 +/- 0.02, Group IIB: 7.13 +/- 0.02 vs. Group I: 7.24 +/- 0.02). Arterial pCO2 was higher in the hypothermic hemorrhagic shock Groups IIA and IIB compared to normothermic group (34.5 +/- 2.2, 37.4 +/- 2.2 vs. 20.3 +/- 20,3 +/- 2.0, p less than 0.05) due to hypothermia-depressed respiration. A higher myocardial O2 consumption and a negative myocardial lactate balance occurred in the normothermic animals during hemorrhagic shock. After resuscitation and rewarming, stroke volume (mL/beat) and cardiac output (L/min) were lower in hypothermic animals with persistent acid-base derangements (12.6 +/- 2.5, 1.3 +/- 3.0, respectively) compared to hypothermic dogs with acid-base correction (20.1 +/- 3.3, 2.2 +/- 0.3) and normothermic dogs (24.6 +/- 3.0, 3.0 +/- 0.3, p less than 0.05), while myocardial O2 extraction and myocardial lactate production were higher. Results suggest hypothermia decreases the metabolic needs and maintains myocardial contractile function in hemorrhagic shock. Hypothermia may have a beneficial effect and, with normalization of acid-base balance, a therapeutic role in hemorrhagic shock.