Study Of Fluid Responsiveness Of Pleth Variability Index And Central Venous Pressure

Objective: Pleth variability index(PVI) is a robust indicator of fluid responsiveness during volume change. In this study, we compared the sensibility of PVI to that of central venous pressure(CVP) when the blood volume changed in patients undergoing intraoperative acute normovolemic hemodilution(ANH) and acute hypervolemic hemodilution(AHH).Methods: Thirty patients were randomly divided into two groups: ANH group(n=15)and AHH group(n=15). All patients received general anesthesia and were mechanically ventilated. Estimated blood volume(EVB) was calculated based on the body weight and sex of each patient. Date were recorded at 5 time-points in the ANH group: baseline(T0),after withdrawal of 5%(T1) and 10% of EVB(T2), and after replacement with an equal volume of 6% hydroxyethyl starch 130/0.4(HES) in 5% of EBV increments to baseline(T3 and T4). There were three time points in the AHH group: baseline(T0), after 5%(T1)and 10% expansion of the EBV with 6% HES(T2). At each time-point, PVI, CVP, and other hemodynamic parameters measurements such as heart rates and blood pressure were obtained. Analysis of regression was performed to show the correlation of PVI and CVP with volume change.Results: During ANH, the value of PVI significantly increased from 16±3 to 20±7after removal of 10% EBV(p<0.05), and returned to a final value of 13±5 after volume replacement. The value of CVP remained unchanged after removal 5% and 10% the EBV,but increased from 11±2 to 14±2 during volume replacement(p < 0.05). During AHH,there was a significant reduction in PVI after 10% expansion of the EBV compared with baseline(from 21±5 to 14±8, p<0.05), and there was a significant increase in CVP after expansion of the EVB compared with baseline(from 9±11 to 2±2, p<0.05). Analysis of regression showed that there was a good correlation between PVI and volume withdraw(r=0.798,p<0.01), between PVI and volume expansion(r=0.596,p<0.05), and betweenCVP and volume expansion(0.682,p<0.05).Conclusion: PVI is a more sensitive parameter for volume than CVP during ANH; on the other hand, both PVI and CVP are well correlated with volume change during AHH.