Acute Metabolic and Endocrine Effects of Induced Hypothermia in Hemorrhagic Shock

Background Hypothermia is considered harmful in trauma patients. In surgery, hypothermia is occasionally used to reduce metabolism and protect the brain. Recent studies in animals have also shown protective effects of hypothermia in hemorrhagic shock. The aim of this study was to evaluate the metabolic and endocrine effects of induced hypothermia in hemorrhagic shock. Methods Half of the individually calculated blood volume was removed from 17 anesthetized piglets. They were then randomized to normothermia or hypothermia and followed for 4 hours after hemorrhage. Results In the hypothermic pigs, arterial PO2 increased from 10.3 +/- 0.7 to 16.4 +/- 0.9 kPa, but it remained unchanged in the normothermic group. The serum levels of potassium increased from 3.9 +/- 0.2 to 5.0 +/- 0.2 mmol/L in the normothermic group. In the hypothermic pigs, the potassium levels temporarily decreased from 3.8 +/- 0.1 to 3.0 +/- 0.1 mmol/L but then returned to baseline levels. The levels of serum catecholamines surged in both groups during hemorrhage. They remained elevated in normothermic pigs but declined in the hypothermic group. Conclusion In porcine hemorrhagic shock, induced hypothermia increases arterial oxygen tension and stabilizes serum levels of potassium and catecholamines.