Abstract:Objective : To investigate the effect of Shenmai injection on vascular endothelial active facters nitric oxide (NO) and endothelin-1 (ET-1), and pulmonary gas exchange induced by tourniquet deflation in patients undergoing lower extremity surgery. Method : Twenty-six patients scheduled for unilateral lower extremity surgery were randomly divided into 2 groups: control group (group C, n=14) and Shenmai injection group (group SM, n=12). All the patients agreed to a combined spinal-epidural anesthesia at the L2 -L3 interspace and a radial artery catheter was placed for sampling. Patients in group SM were injected Shenmai injection 0.6 mL·kg-1 and physiological saline 100 mL,while patients in group C were injected equal volume of normal saline instead 15 min before tourniquet inflation. Blood samples which were used for blood gas analysis and measurement of nitric oxide (NO) and endothelin-1 (ET-1) were taken before tourniquet inflation (T0, baseline) and 30 min (T1), 2 h (T2), 6 h (T3), 24 h (T4) after tourniquet deflation. Result : Compared with the baseline values at T0, in group C at T3 PaO2 and the levels of NO were significantly decreased, while PA-aDO2 and the levels of ET-1 at T3 were significantly increased (P<0.05 or P< 0.01), in group SM, the levels of NO at T3 were significantly decreased (P<0.05 ). Compared with group C, the changes of PaO2, PA-aDO2, NO and ET-1 were significantly mitigated in group SM. Conclusion : The concentrations of NO and ET-1 is connected with the pulmonary gas exchange impairment induced by tourniquet application. Shenmai injection can improve the pulmonary gas exchange based on rising the level of NO, reducing the level of ET-1.