ObjectiveTo investigate the effect of lung-protective ventilation mode on stroke volume variation (SVV) in patients receiving selected thoracotomy. MethodsTwenty patients of the American Society of Anesthesiology (ASA) class Ⅰ or class Ⅱ were selected for this study, with no drugs administrated before operation. In addition to standard hemodynamic monitoring, SVV and cardiac index (CI) were recorded at the following eight time points: spontaneous breathing when awake and at supine position (T₁), spontaneous breathing when awake and at lateral position (T₂), general anesthesia with two-lung ventilation and at supine position (T₃), general anesthesia with one-lung ventilation under lung-protective strategy and at supine position (T₄), general anesthesia with two-lung ventilation and at lateral position (T₅), general anesthesia with one-lung ventilation under lung-protective strategy and at lateral position (T₆), combined anesthesia with one-lung ventilation under lung-protective strategy when skin incision (T₇), and combined anesthesia with one-lung ventilation under lung-protective strategy when pleural dissection (T₈). The changes of heart rate (HR), mean arterial pressure (MAP), SVV, and CI were observed at the above eight time points; and the relation of SVV with HR, MAP and CI was discussed. Homogenity test of variances was used to analyze the data of the four indices; the use of further statistical scheme was judged by the result of homoscedasticity. A Pearson correlation analysis was used for SVV with HR, MAP, and CI. ResultsHomogenity of variance test showed that the changes of SVV and HR at T₁ -T8 had no significant difference (P>0.05), while the changes of MAP and CI had significant difference (P<0.05). LSD multiple comparison indicated significant differences for the followings (P<0.05): SVV between T₂ and T₅, CI among T₁ and T_3-8, CI among T₂ and T_4,6,7,8, MAP among T₁ and T_3,4,6,7,8, MAP among T₂ and T_3,4,6,7,8, and MAP between T₄ and T₅. We also found that SVV had negative correlation with CI (r=-0.267, P=0.018). ConclusionThe change of body position (from supine to lateral position) in patients without hypovolemia before operation has no significant impact on SVV and HR; one-lung ventilation under lung-protective strategy has no noticeable effects on SVV, HR, MAP or CI. Anesthetic factor can cause the drop of MAP and CI, and the action of passive position change under anesthesia can result in the rise of MAP and CI. Alteration of SVV has negative correlation with CI, but the correlation is weak.