Effect of environmental hypothermia exposure on hemodynamics and oxygen metabolism during general anesthesia in a pig model of hemorrhagic shock

Abstract

Objective To evaluate the effect of environmental hypothermia exposure on hemodynamics and oxygen metabolism during general anesthesia in a pig model of hemorrhagic shock. Methods Twelve pathogen-free Bama miniature pigs of both sexes, weighing 20-24 kg, were divided into 2 groups(n=6 each)using a random number table: room temperature group(group RT)and environmental hypothermia group(group EH). The animals inhaled 2% isoflurane for maintenance of anesthesia.The pigs were placed at room temperature(20-22℃)and at low temperature(-10 ℃)in group RT and group EH, respectively.Hemorrhagic shock was induced by withdrawing blood from the right femoral artery within 20 min(30 ml/kg). Before withdrawing blood(T1), immediately after the end of withdrawing blood(T2), and at 1, 2, 3, 4 and 5 h of shock(T3-7), heart rate, mean arterial pressure, mean pulmonary artery pressure, cardiac index and systemic vascular resistance index were recorded.Blood samples were collected from the right femoral artery and internal jugular vein for blood gas analysis, and lactic acid concentrations, hemoglobin, arterial oxygen partial pressure, arterial oxygen saturation, and mixed venous oxygen saturation were recorded.Oxygen delivery index, oxygen consumption index and O2 extraction rate were calculated. Results Compared with group RT, heart rate at T3-7, cardiac index and oxygen delivery index at T5-7, oxygen consumption index at T1-7, O2 extraction rate at T2-6, and lactic acid concentrations at T5-7 were significantly decreased, and mean arterial pressure at T4, 5, mean pulmonary artery pressure at T4-7, systemic vascular resistance index at T3-7, and mixed venous oxygen saturation at T2-6 were increased in group EH(P<0.05). Conclusion Environmental hypothermia exposure inhibits cardiac compensatory responses, increases the peripheral vascular resistance, and aggravates oxygen dysmetabolism during general anesthesia in a pig model of hemorrhagic shock. Key words: Hypothermia; Shock, hemorrhagic; Hemodynamics; Oxygen consumption