Correlation Of Inferior Vena Cava Blood Flow Measured By Ultrasound With Volume Status And Fluid Responsiveness

Objects To investigate the correlation between the changes of inferior vena cava（IVC）morphological or blood flow assessed by ultrasound with fluid-responsiveness.Methods In our study,44 patients were selected preparing for elective surgery undergoing general anesthesia and mechanical ventilation.They were regarded as responders and non-responders according to whether the cardiac index（CI）of them increase more than 10%or not after fluid loading.All patients were performed with tidal volume challenge and fluid challenge,respectively,then the maximum and minimum values of anterior-posterior diameter(AP_max,AP_min),longitudinal diameter(LA_max,LA_min)and maximum peak velocity(V_max)of centripetal flow of IVC were measured by ultrasound and the maximum blood flow（Q）calculated after.Blood pressure,heart rate,cardiac index（CI）and stroke volume variation（SVV）were continuously monitored using a noninvasive cardiac output monitor.All data were analyzed using SPSS19.0 statistical software,and the results were expressed as P<0.05 for statistically significant differences.Result A total of 44 patients were finally enrolled,28 cases were responders,11cases were non-responders,and 5 patients were excluded.There was no difference in general information between the two groups（p>0.05）.After tidal volume challenge,the AP variability and SVV in the responders were significantly higher than those in the non-responders,mean values of AP and V_max were smaller than the later（p<0.05）,the changes in LA,V_max,Q and CI were not significant.Before fluid challenge,the AP variability and SVV of responders were high and then became significantly lower after,and the V_max,Q and CI Significantly increased（p<0.05）,the differences of all the index between two groups became non-significant.For responders,there was a good positive correlation between V_max,Q and CI（r 0.736,0.759,respectively）,which was less affected by ventilation tidal volume（p<0.05）;and SVV had a well correlation with AP variation and V_max at tidal volume challenging（r 0.679,0.612,respectively）（p<0.05）.For non-responders,the changes of IVC indexes,SVV and CI were not significant before and after both of tidal volume challenge and fluid challenge（p>0.05）.Conclusions Ultrasound assessment of IVC morphologic changes and blood flow velocity are closely related to volume status and valuable for predicting volume responsiveness.Anterior and posterior diameter variability of inferior vena cava is more pronounced than transverse diameter,and increasing mechanical ventilation tidal volume does not avoid false-negative predictive results.The maximum peak velocity(V_max)of centripetal flow of inferior vena cava is less influenced by tidal volume,which has the potential value of predicting fluid responsiveness.