Objective To observe the effect of one-lung ventilation (OLV) on cerebral oxygen balance and energy metabolism during total intravenous anesthesia for thoracoscopic surgery.Methods Thirty patients scheduled for thoracoscopic surgery were selected.After inducing and intubating,patients were assigned to maintenance of anesthesia with propofol by target controlled infusion in order to maintain a bispectral index(BIS) between 40 and 60,and end-tidal partial pressure of carbon dioxide (PETCO2) between 30mmHg and 35mmHg.Mean arterial pressure (MAP),heart rate (HR),SpO2,PetCO2,cerebral blood flow velocity (CBFv),BIS value and nasopharyngeal temperature(NPT) were measured,always with the patients in the lateral position,in four phases:10min after beginning twolung ventilation (TLV),15 min after beginning OLV (OLV + 15),30min after beginning OLV (OLV + 30) and 60 min after beginning OLV(OLV + 60).Blood samples were drawn simultaneously and analyzed within 5min.The Da-jvO2,CERO2,CMRO2,Da-jvLac and Da-jvGlu at each phase were calculated.Results In all patients,a decrease in PaO2 [(172±85) vs (428±42);(162±54) vs (428±42);(185±61) vs (428±42)] and MAP [(70±10) vs (81 ±11) ; (71 ± 12) vs (81 ± 11)] occurred during OLV (t =15.02,13.14,23.25,20.16,18.02,all P ＜ 0.05).SjvO2 at the phase:OLV + 15 and OLV + 30 were significantly lower than those at TLV [(54.0 ± 1.2) ％ vs (65.0 ± 0.8) ％ ;(55.0±1.5)％ vs (65.0 ±0.8)％] (t =3.12,2.14,all P＜0.05).Ca-jvO2[(50 ± 12)％ vs(40 ± 12)％ ;(54±11)％ vs (40 ± 12)％],CMRO2 [(186 ±40) vs (162 ± 35);(191 ±24) vs (162 ±35)]and CERO2 [(36 ± 12) vs (30 ± 1 1) ; (35 ± 10) vs (30 ± 11)] atthephase:OLV + 15 andOLV + 30weresignificantlyhigher than those at TLV (t =5.23,4.28,1.86,2.01,8.21,10.11,all P ＜ 0.05).After OLV,Da-jvGlu [(0.45 ± 0.10) vs (0.22 ± 0.30) ; (0.52 ± 0.20) vs (0.22 ± 0.30) ; (0.40 ± 0.20) vs (0.22 ± 0.30)] significantly increased (t =6.45,12.03,15.10,all P ＜ 0.05).The differences of Da-jvLac and CBFv at every phase were not significant (P ＞0.05).Conclusion During total intravenous anesthesia,OLV resulted in an increase of consumption of cerebral oxygen and energy.It may be not good for cerebral oxygen balance and energy metabolism.The efficient prevention is necessary clinically.