The Ability Of Pleth Variability Index To Predict Fluid Responsiveness In Mechanically Ventilated Patients Under General Anaesthesia

Backgroud:Respiratory variations in the pulse oximeter plethysmographic waveform amplitude(ΔPOP) are sensitive to changes in preload and can predict fluid variability in mechanically ventilated patients.However, they cannot be easily calculated from a bedside monitor. Pleth Variability Index(PVI, Masimo Corp.,Irvine, CA)is a new algorithm that automatically calculatesΔPOP. The aim of our study was to test the ability of this new device to fluid responsiveness in mechanically ventilated patients.Objective:To evaluate the ability of pleth variability index (PVI) in predicting fluid responsiveness in mechanically ventilated patients under general anesthesia.Methods:Twenty-five patients were enclosed in this study. Induction of anesthesia was performed with dormicum (0.05mg·kg-1),propofol(1-2mg·kg-1)and fentanily(3μg·kg-1), and orotracheal intubation was facilitated with pancuronium(0.8-1mg·kg-1). Anesthesia was maintained with continous infusions of propofol in order to keep a Bispectral Index (Aspect 1000, Aspect Medical Systems, Natick, MA) between 40 and 50. All patients' lungs were ventilated in a volume of 10 ml/kg of body weight at a frequency of 8-12 cycles/min. Following anesthesia induction, PVI was continuously displayed by the Masimo Radical 7. All patients were also monitored with Vigileo/FloTrac system. Haemodynamic data (CI,SVV,MAP,HR,CVP,PVI,PI) were recorded before and after volume expansion(VE)(Hetastar 6%,7ml/kg). Fluid responsiveness was defined as an increase in CIΗ≥15%(ΔCI≥15).Results:1,SVV and PVI were significantly higher in the responders (16.0±2.6% and 20.5±3.7%) than those in the non-responders (11.6±1.4% and 13.8±2.6%) respectively (P<0.05). 2,There was a significant relationship between PVI before volume expansion and change in CI after volume expansion(r=0.683, P<0.01),the same as the changes of SVV(r=0.600,P<0.01).3,A SVV threshold of 13.5% before volume expansion was able to discriminate the responders from the non-responders with a sensitivity of 88.2% and a specificity of 87.5%. The threshold for PVI was 15.5%,the same sensitivity of 88.2% and specificity of 87.5% were obtained.Conclusion:PVI, one of the dynamic indices, can predict fluid responsiveness non-invasively in mechanically ventilated patients during general anesthesia. Objective:To evaluate the ability of Pleth Variability Index in predicting fluid responsiveness in patients ventilated with different tidal volume under general anesthesia.Methods:Fifty ASAⅠorⅡpatients aged 18-75 yr undergoing elective gastrointestinal surgy were randomly divided into 2 qroups:group C(VT=8mL/kg, n=25) and group S(VT=10mL/kg n=25). Induction of anesthesia was performed with dormicum (0.05mg·kg-1), propofol(1-2mg·kg-1) and fentanily (3μg·kg-1), and orotracheal intubation was facilitated with pancuronium(0.8-1mg·kg-1). Anesthesia was maintained with continous infusions of propofol in order to keep a Bispectral Index (Aspect 1000, Aspect Medical Systems, Natick, MA) between 40 and 50. All patients were studied after induction of general anesthesia. PVI was continuously displayed by the Masimo Radical 7. All patients were also monitored with Vigileo/FloTrac system. Haemodynamic data (CI,MAP,HR,CVP,SVI,PVI) were recorded before and after volume expansion(VE)(Hetastar 6%,7ml/kg). Fluid responsiveness was defined as an percentage increase in CI (ΔCI)≥15%.Results:1,The PVI threshold value of groups C and group S that responsed to volume expansion (17.4±5.1,22.1±5.7, respectively)was significantly higher than that of nonresponsed to volume expansion(10.2±2.3,13.1±3.1, respectively)(P< 0.01).2. There was a significant relationship between PVI before volume expansion and change in CI after volume expansion in both of the two groups(rc=0.566,rs=0.683,respectively)(P<0.01).3,A PVI threshold of 13.5% before volume expansion of group C was able to discriminate between responders and non-responders with a sensitivity of 81.3% and a specificity of 88.2%, while in group S, the threshold of 15.5% could obtain the similar consequence(a sensitivity of 88.9% and a specificity of 87.5%);Conclusion:PVI can predict fluid responsiveness non-invasively in mechanically ventilated patients with a tidal volume of 8mL/kg and lOmL/kg under general anaesthesia. The PVI threshold value that predicting fluid responsiveness is 13.5% and 15.5% respectively.