Proving the effectiveness of three dynamic indices to predict fluid responsiveness in septic mechanically ventilated patients

Introduction

Fluid responsiveness is still a cornerstone in managing patients with severe sepsis and septic shock. Recently new technologies have been generated for facilitating the accuracy of predicting fluid responsiveness at the bedside, based on cardiopulmonary interaction [1, 2]. We evaluated the effectiveness and accuracy of three dynamic indices, currently available in intensive care monitoring devices, which are pulse pressure variation (PPV) [3], stroke volume variation (SVV) and pulse oximetry plethysmographic waveform variation (POPV) in septic mechanically ventilated patients [4].

Methods

A prospective clinical trial was conducted in 20 septic patients 18 years of age and older who had invasive blood pressure monitoring with an intraarterial cannula. PPV, SVV and POPV (%) were calculated and compared with the percentage cardiac index (CI) change. Patients with a CI increase induced by volume expansion >15% were classified as responders, and <15% as nonresponders. A parametric paired t test was used to compare hemodynamic parameters at baseline and after volume expansion. Student's t test was used to compare hemodynamic parameters in the responders and nonresponders groups. Receiver operating characteristic curves were used to evaluate the predictive value of various indices on fluid responsiveness. P < 0.05 was considered significant.

Results

We found a strong correlation existed for PPV for detection of a volume expansion-induced change in CI (r² = 0.794), followed by SVV (r² = 0.667), and POPV (r² = 0.633). The areas under the receiver operating characteristic curves were 0.96 for PPV (P < 0.001), 0.92 for SVV (P = 0.001), and 0.85 for POPV (P = 0.008). Respiratory variation in POPV exceeding 14% (sensitivity of 72%, specificity of 90%), SVV exceeding 11% (sensitivity 90%, specificity 92%), allowed detection of PPV exceeding 12% (sensitivity 84%, specificity 96%).

Conclusion

In the septic mechanically ventilated patients, PPV is the most effective dynamic parameter for predicting fluid responsiveness; all of PPV, SVV and POPV are well correlated with the percentage change of CI.