Abstract: Background　Available studies have shown that in the monitoring of patient volume status and volume responsiveness by the FloTrac/Vigileo system，stroke volume variation（SVV） ≥ 13% indicates the patient capacity is insufficient，otherwise it is relatively sufficient，and when the tidal volume（VT） ≤ 5 ml/kg，SVV can not accurately reflect patient volume status and volume responsiveness.However，there is no clear conclusion about the specific relationship between VT and SVV.Objective　To investigate the effects of different VT on SVV in open gastrointestinal surgery，and to analyze the feasibility and accuracy of using SVV to evaluate patient volume responsiveness under different VT.Methods　Sixty patients undergoing elective open gastrointestinal surgery in Weifang People's Hospital from October 2018 to June 2019 were selected.After mechanical ventilation，the VT was adjusted to 6，8，10 and 12 ml/kg，respectively，and the mean arterial pressure（MAP），heart rate（HR），SVV and CI values were recorded.When the SVV measured at VT of 8 ml/kg was ≥13%，then rapid intravenous rehydration of 500 ml 6% hydroxyethyl starch 130/0.4 in 0.9% sodium chloride injection was performed.Then the MAP，HR，SVV and the CI under four VT conditions were measured and recorded again.Results　Before rapid intravenous rehydration therapy，MAP and HR were similar under four different VT conditions（P>0.05），while SVV differed significantly（P<0.05）.The SVV under four different VT conditions increased with the increase VT，to be specific，SVV at VT=8 ml/kg was higher than that at VT=6 ml/kg，SVV at VT=10 ml/kg was higher than that at VT=6 ml/k and VT=8 ml/kg，and SVV at VT=12 ml/kg was higher than that at VT=6 ml/k，VT=8 ml/kg and VT=10 ml/kg（P<0.05）.After rapid rehydration therapy，MAP and HR were still similar under four different VT conditions（P>0.05），while SVV still differed significantly（P<0.05）.When the ΔCI（the difference of CI before and after rapid rehydration therapy） ≥15% was defined as having response to rehydration therapy，the AUC of SVV in determining the volume responsiveness at VT=6 ml/kg，8 ml/kg，10 ml/kg and 12 ml/kg，was 0.625，0.884，0.873，and 0.856，respectively，and the corresponding diagnostic threshold was 10%，13%，16%，and 19%，respectively.Conclusion　VT has an effect on SVV.The greater the VT，the larger the measured SVV value.The SVV monitored under VT of 6-12 ml/kg can determine the blood volume status of the patient.But compared with at VT of 6 ml/kg，the SVV measured at VT=8，10，12 ml/kg can more accurately determine the capacity status and volume responsiveness of the patient under mechanical ventilation.The critical values of SVV under different VT are different.The critical values of SVV are 10%，13%，16%，and 19%，respectively，when VT=6，8，10，12 ml/kg.

Key words: Digestive system surgical procedures, Gastrointestinal tract, Tidal volume, Stroke volume, Stroke volume variability, Cardiac volume, Cardiac index

摘要： 背景　现有研究表明，患者使用FloTrac/Vigileo系统监测患者容量状态及容量反应性时，若每搏输出量变异度（SVV）≥13%，患者容量不足，反之患者容量相对充足，且当潮气量（VT）≤5 ml/kg时，SVV无法准确监测患者的容量状态和容量反应性。但是对于VT与SVV的具体关系尚未有明确结论。目的　探讨开放性胃肠道手术中不同VT对SVV的影响，并分析不同VT时使用SVV评价患者容量反应性的可行性和准确性。方法　选择2018年10月—2019年6月在潍坊市人民医院择期行开放性胃肠道手术的患者60例，机械通气后分别将VT调整至6、8、10、12 ml/kg，记录平均动脉压（MAP）、心率（HR）、SVV和心排血指数（CI），若VT=8 ml/kg时测得SVV≥13%，则快速补液500 ml，再次测量并记录4个不同VT时MAP、HR、SVV、CI。结果　快速补液前4个不同VT时MAP、HR比较，差异均无统计学意义（P>0.05）。快速补液前4个不同VT时SVV比较，差异有统计学意义（P<0.05）；其中VT=8 ml/kg时SVV高于VT=6 ml/kg时，VT=10 ml/kg时SVV高于VT=6 ml/kg和VT=8 ml/kg时，VT=12 ml/kg时SVV高于VT=6 ml/kg、VT=8 ml/kg和VT=10 ml/kg时（P<0.05）。快速补液前后不同VT时MAP、HR比较，差异均无统计学意义（P>0.05）。快速补液前后不同VT时SVV比较，差异均有统计学意义（P<0.05）。以ΔCI≥15％为标准，VT=6 ml/kg时，SVV判断容量反应性的受试者工作特征曲线下面积（AUC）为0.625，VT=8 ml/kg、VT=10 ml/kg、VT=12 ml/kg时，SVV判断容量反应性的AUC为0.884、0.873、0.856，4个不同VT时SVV的诊断阈值分别为10%、13%、16%、19%。结论　VT对SVV有影响，VT越大，测得的SVV数值越大；VT=6~12 ml/kg时监测的SVV均可以判断患者容量反应性；与VT=6 ml/kg相比，VT=8、10、12 ml/kg时测得的SVV更能准确判断患者机械通气状态下的容量反应性；不同VT时SVV临界值不同，VT=6、8、10、12 ml/kg时SVV的临界值分别为10%、13%、16%、19%。

关键词: 消化系统外科手术, 胃肠道, 潮气量, 每搏输出量, 每搏输出量变异度, 心脏容量, 心排血指数