Abstract： Objective To observe the effect of total intravenous anesthesia (TIVA) on intrapulmonary shunt fraction and arterial oxygenation during one-lung ventilation (OLV) for thoracoscope surgery.Methods Forty patients scheduled for thoracoscope surgery were randomly assigned to two groups ( n =20),group of TIVA (A) and group of intravenous anesthesia combined with inhalational anesthesia(B).After inducing and intubating,patients were assigned to maintenance of anesthesia with propofol ( group A)or with sevoflurane ( group B) in order to maintain a BIS between 40 and 60.Mean arterial pressure (MAP),heart rate (HR),SpO2 and Paw were measured in four phases,always in the lateral position,10min after beginning two-lung ventilation (TLV),15 min after beginning OLV (OLV + 15 ),30 rain after beginning OLV ( OLV + 30) and 60 min after beginning OLV ( OLV + 60).Blood samples were drawn simultaneously and analyzed within 5 min.The Qs/Qt at each phase was calculated.Adverse events including hypotension,bradycardia,hypoxemia,delayed emergence and restlessness in recovery period were recorded.Results In all patients,a decrease in PaO2 and an increase in the Qs/Qt occurred during OLV were observed.But PaO2 values in group A were significantly higher than those in group B ( 177 ±88 vs 125 ±63;150 ±65 vs 110 ±67;188 ±69 vs 128 ±52) ( P ＜0.05).The Qs/Qt in group B was significantly higher than those in group A (34.2 ±5 vs 28.8 ±2;38.4 ±8 vs 32.1 ±6;37.1 ±2 vs 29.5 ±2,P ＜0.05).MAP values in group A were significantly lower than those in group B at the phase:OLV + 15 and OLV +30(72 ± 10 vs 88 ± 14;74 ± 12 vs 89 ± 10) ( P ＜ 0.05 ).The incidence of hypotension and delayed emergence in group A was higher than those in group B ( 10 case vs 4 case;9 case vs 2 case).The incidence of restlessness in recovery period in group B was more than those in group A (9 case vs 3 case).The differences between two groups were significant ( P ＜ 0.05).Conclusions Compared with sevoflurane-sufentanyl combined anesthesia,TIVA with propofol can efficiently decrease intrapulmonary shunt fraction and improve arterial oxygenation during OLV for thoracoscope surgery,which is good for the prevention of hypoxemia.