Effect of hypothermia on coagulatory function and survival in Sprague-Dawley rats exposed to uncontrolled haemorrhagic shock.

BACKGROUND: Acute coagulopathy, hypothermia, and acidosis are the lethal triad of conditions manifested by major trauma patients. Recent animal studies have reported that hypothermia improves survival in animals subjected to controlled haemorrhagic shock. The objective of this study was to investigate the effect of hypothermia on coagulation in rats subjected to uncontrolled haemorrhagic shock.
METHODS: Thirty-two male Sprague-Dawley rats were randomly divided into four groups: normothermia (control, group N), hypothermia (group H), hypothermic haemorrhagic shock (group HS), and normothermic haemorrhagic shock (group NS). Haemorrhagic shock was induced by splenic laceration. Capacity for coagulation was measured by rotation thromboelastometry (ROTEM(®)), and was measured at baseline as well as the end of the shock and resuscitation periods. Survival was observed for 48 h post-trauma.
RESULTS: Baseline parameters were not different amongst the groups. Rats exposed to hypothermia alone did not differ in coagulation capacity compared to the control group. Clot formation time (CFT) and maximal clot firmness (MCF) in group HS decreased as the experiment progressed. Maximal clot firmness time (MCFt) in groups H and HS was significantly prolonged during shock and resuscitation compared with that in group NS. In group NS, MCF did not change significantly, but MCFt was reduced compared with baseline. Group HS had poor survival when compared with normovolaemic groups.
CONCLUSION: Blood clotted less firmly in traumatic haemorrhagic shock, and hypothermia prolonged clotting. However, clot firmness maximised rapidly under normothermic haemorrhagic shock. Haemorrhage would continue for a longer time in hypothermic haemorrhagic shock. Survival of hypothermic shock was not significantly different compared to that of normothermic haemorrhagic shock.