Moderate hypothermia prevents cell injury in rats with severe haemorrhagic shock

Abstract

Abstract Background This study aimed to evaluate a possible protective and therapeutic effect of mild to moderate hypothermia in severe haemorrhagic shock. Brainstem is one of the most sensitive tissues to oxidative stress in the early phase of haemorrhagic shock. The haemorrhagic oxidative stress at various core temperatures was studied using reduced glutathione (GSH) levels and thiobarbituric acid reactive substances (TBARS) as markers of lipid peroxidation in brainstem homogenate. Methods Forty rats were divided into four groups, of which one constituted the non-bleeding normothermia control group. In all of the three study groups, the rats were bled to 40 per cent of their estimated blood volume while they were being held at normothermia, mild (32°C) or moderate (28°C) hypothermia. Mean arterial pressure, rectal temperature, heart and breathing rates were recorded during the procedures. After 1 h of shock, tissue samples were removed by craniectomy. Results The tissue levels of TBARS increased significantly in normothermic and mildly hypothermic haemorrhagic shock groups (10·74 and 8·26 nmol g−1) compared with control (3·50 nmol g−1) (P < 0·001). However, the tissue TBARS level in the moderately hypothermic group was only minimally increased (4·53 nmol g−1). GSH levels fell slightly in normothermic and mildly hypothermic bleeding rats, and were unchanged in moderately hypothermic rats. Conclusion The TBARS level, which was a predictor of oxidant damage, changed slightly during severe haemorrhagic shock when the rats were moderately hypothermic. Hypothermia had a protective effect against cell injury during haemorrhagic shock. Tissue TBARS levels correlated well with the degree of tissue damage; lower levels suggested hypothermic protection.