Effects of environmental hypothermia on hemodynamics and oxygen dynamics in a conscious swine model of hemorrhagic shock.

BACKGROUND Hypothermia is associated with poor outcome in trauma patients; however, hemorrhagic shock (HS) model with anesthetized swine was different from that of clinical reality. To identify the effects of environmental hypothermia on HS, we investigated hemodynamics and oxygen dynamics in an unanesthetized swine model of HS under simulating hypothermia environment. METHODS Totally 16 Bama pigs were randomly divided into ambient temperature group (group A) and low temperature group (group B), 8 pigs in each group. Venous blood (30 mL/kg) was continuously withdrawn for more than 15 minutes in conscious swine to establish a hemorrhagic shock model. Pulmonary arterial temperature (Tp), heart rate (HR), mean arterial pressure (MAP), pulmonary arterial pressure (PAP), pulmonary arterial wedge pressure (PAWP), central venous pressure (CVP), cardiac output (CO), hemoglobin (Hb), saturation of mixed venous blood (SvO2) and blood gas analysis were recorded at the baseline and different hemorrhagic shock time (HST). The whole body oxygen delivery indices, DO2I and VO2I, and the O2 extraction ratio (O2ER) were calculated. RESULTS Core body temperature in group A decreased slightly after the hemorrhagic shock model was established, and environmental hypothermia decreased in core body temperature. The mortality rate was significantly higher in group B (50%) than in group A (0%). DO2I and VO2I decreased significantly after hemorrhage. No difference was found in hemodynamics, DO2I and VO2I between group A and group B, but the difference in pH, lactic acid and O2ER was significant between the two groups. CONCLUSION Environmental hypothermia aggravated the disorder of oxygen metabolism after hemorrhagic shock, which was associated with poor prognosis.