The pleth variability index as an indicator of the central extracellular fluid volume in mechanically ventilated patients after anesthesia induction: Comparison with initial distribution volume of glucose

BACKGROUND: The pleth variability index (PVI) has been demonstrated to be a useful, noninvasive indicator of continuous fluid responsiveness. Whether PVI can be used to assess the changes of intravascular volume status remains to be elucidated. MATERIAL AND METHODS: Using correlation analysis and receiver operating characteristic (ROC) curves, we sought a correlation between PVI and the initial distribution volume of glucose (IDVG), evaluating PVI as an indicator of the central extracellular fluid volume after anesthesia induction in patients undergoing elective abdominal surgery. RESULTS: Strong negative correlations existed between IDVG and PVI (r=-0.72), IDVG, and pulse pressure variation (PPV) (r=-0.73), and between IDVG and systolic pressure variation (SPV) (r=-0.53), P<0.01. Strong positive correlations existed between PPV and PVI (r=0.66), PVI and SPV (r=0.49), and between PPV and SPV (r=0.59), P<0.01. The areas under the ROC curve of IDVG, PVI, and SPV were significantly different from the area under a reference line. The optimal cutoff values (followed by sensitivity and specificity in parentheses) comparable to PPV over 11% as the threshold of hypovolemia were IDVG 94.5 mL/kg (75%, 100%), PVI 13% (91.7%, 77.8%), and SPV 7% (41.7%, 100%). CONCLUSIONS: Our results show that strong correlations exist among IDVG, PVI, PPV, and SPV in the evaluation of volemia. PVI can serve as a useful, noninvasive indicator of continuous central extracellular fluid volume for those patients not requiring invasive hemodynamic monitoring, but needs attention to changes in intravascular volume status for optimal fluid management.