Effects of low ambient temperature on hemodynamics and oxygen dynamics in a porcine hemorrhagic shock model

Objective 　To investigate the effects of low ambient temperature on hemodynamics and oxygen dynamics in a porcine hemorrhagic shock model. Methods 　Thirty-two healthy adult Bama miniature pigs were randomly divided into four groups (8 each): control (group C), shock under room temperature (22℃, group R), shock under low ambient temperature (–10℃, group L) and shock under normal body temperature (keep pulmonary arterial temperature ranged from 38.5 to 39.5℃, group N). The hemorrhagic shock model was reproduced by venous bleeding (40% of total blood volume), and the core temperature (pulmonary arterial temperature and rectal temperature), 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 before reproduction of shock and at different time points after hemorrhagic shock. The whole body oxygen delivery index (DO2I), oxygen uptake index (VO2I), and oxygen extraction ratio (O2ER) were calculated. Results 　Four pigs died in group N during the experiment, meanwhile, no pig died in other groups. The core temperature in group C, R and L decreased significantly compared with group N (P<0.05), and the core temperature in group L was significantly lower than that in groups C and R from 120 minutes after shock. No difference was found in hemodynamics, oxygen dynamics and prognosis between group R and group L. The HR and VO2I in group N were significantly higher than those in group L and group R, while there was no difference in other indices between the 3 groups. Conclusion 　The hemodynamics and oxygen dynamics indices don't worsen in hemorrhagic shock pigs under low ambient temperature, possibly resulting from induced hypothermia caused by anesthesia.