Clinical research of velocity time integral variation of the carotid artery for predicting volume responsiveness in patients me-chanically ventilated at low tidal volumes
Objective To evaluate the accuracy of velocity time integral variation(△ VTI)of the carotid artery for predicting volume responsiveness in patients mechanically ventilated at a low tidal volume.Methods A total of 50 patients,aged 50 to 70 years,American Society of Anesthesiologists(ASA)grade Ⅰ or Ⅱ,who underwent elective gastrointestinal surgery under general anes-thesia were selected.All the patients were ventilated at a low tidal volume(tidal volume 7 ml/kg)after induction of tracheal intubation under general anesthesia.When the hemodynamics became stable[before the volume loading test(VE)],the velocity time integral(VTI)and peak velocity(Vpeak)were measured by a pulsed Doppler in the middle of the carotid.The tidal volume was then temporarily changed to 9 ml/kg and VE was conducted after connecting the Vigileo system.The stroke volume(SV)was recorded before and after VE,and the stroke volume variation(△ SV)was calculated.According to △ SV,the patients were divided into two groups:a response group(group R,△SV≥15％,n=27)and a non-response group(group N,△SV＜15％,n=23).Then,all the patients were ventilated at a low tidal volume(tidal volume 7 ml/kg),when the hemodynamics became stable(after VE),VTI and Vpeak were measured in the carot-id.The △ VTI and peak velocity variation(△ Vpeak)were calculated.Furthermore,the mean arterial pressure(MAP),and heart rate were recorded before and after VE.A receiver operating characteristic(ROC)curve was plotted to analyze the △ VTI and △ Vpeak,while the cut-off value,sensitivity,specificity,area under the curve(AUC)and 95％confidence interval(CI)were calculated at the opti-mal Youden index.The accuracy of △ VTI and △ Vpeak in predicting volume responsiveness in patients mechanically ventilated at a low tidal volume was evaluated.Results Compared with those before VE,both groups showed increases in MAP(all P＜0.05),but de-creases in heart rate,△ VTI and △ Vpeak after VE(all P＜0.05).Compared with group N,group R presented decreases in MPA(P＜0.05)and increases in heart rate,△ VTI and △ Vpeak before VE(P＜0.05);and showed decreases in MAP(P＜0.05),and increases in △ VTI after VE(P＜0.05),without statistical differences in heart rate and △ Vpeak(all P＞0.05).According to ROC analysis,the cut-off value of△ VTI in predicting volume responsiveness in patients mechanically ventilated at a low tidal volume was 12.35％,with a sensitivity of 74.1％and a specificity of 91.3％,and the AUC was 0.902[(95％CI 0.820～0.984),P＜0.05].The cut-off value of △ Vpeak in predicting volume responsiveness in patients mechanically ventilated at a low tidal volume was 10.70％,with a sensitivity of 55.6％and a specific-ity of 95.7％,and the AUC was 0.873[(95％CI 0.730,0.943),P＜0.05].Conclusion △ VTI can accurately predict volume respon-siveness in patients mechanically ventilated at a low tidal volume.
Velocity time integralLow tidal volumesFluid responsiveness
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