The Effect Of Tidal Volume Challenge On The Assessment Of Fluid Responsiveness Of Dynamic Indicator Under The Mode Of Pressure-controlled Ventilation Volume Guaranteed

Objective To investigate the effect of tidal volume challenge on the prediction of volume responsiveness of patients with pulse pressure variability and stroke volume variability under the pressure-controlled ventilation volume guaranteed mode.Methods Sixty patients of both sexes,aged 18～64 yr,with body mass index of 18.5～23.9 kg/m²,of American Society of Anesthesiologists physical statusⅠorⅡ,scheduled for elective resection of gastrointestinal tumor with general anesthesia,were enrolled in the study.After intravenous anesthesia induction and before the start of the surgery,the patients were firstly ventilated by PCV-VG with tidal volume（V_T）6 ml/kg predicted body weight,the maximum airway pressure was set as 30mm H₂O,positive end expiratory pressure was set as 3～5cm H₂O,P_ETCO₂was maintained as 35～45mm Hg.And the pulse pressure variability（PPV₆）and stroke volume variability（SVV₆）were recorded,then TVC was performed,which increased V_Tfrom 6 ml/kg to 8 ml/kg predicted body weight for 1 minute,and the PPV₈and SVV₈were recorded.The variation of PPV and SVV（ΔPPV andΔSVV）were calculated after TVC（ΔPPV=PPV₈–PPV₆,ΔSVV=SVV₈–SVV₆）.When TVC was completed,the V_Twas reduced back to 6ml/kg predicted body weight for fluid challenge.Increase in cardiac index after fluid challenge≥15% was considered to be a positive response.Eligible patients were divided into groups of responders or non-responders.The receiver operating characteristic curve for each indicator in determining fluid responsiveness was drawn.Results The results of receiver operating characteristic curve analysis showed that the area under the curve for PPV₆,SVV₆,PPV₈,SVV₈,ΔPPV andΔSVV in determining fluid responsiveness（95%confidence interval）was 0.57（0.43～0.72）,0.62（0.47～0.76）,0.83（0.73～0.87）,0.76（0.64～0.88）,0.95（0.90～1.00）and 0.91（0.86～0.99）,respectively,the cutoff value of PPV₈,SVV₈,ΔPPV andΔSVV was 10.5%,13.5%,4.5% and 5.5%,respectively,the sensitivity was 75%,78%,88% and 85%,respectively,and the specificity was 88%,87%,95% and 98%,respectively.Conclusion The ability to assess the fluid responsiveness ofΔPPV andΔSVV was better than that of PPV and SVV during the low-tide ventilation under PCV-VG ventilation mode.Tidal volume challenge is helpful to improve the ability of PPV and SVV to assess the fluid responsiveness.