Passive leg raising as an indicator of fluid responsiveness in patients with severe sepsis

In the management of critically ill patients, the assessment of volume responsiveness and the decision to administer a fluid bolus constitute a common dilemma for physicians. Static indices of cardiac preload are poor predictors of volume responsiveness. Passive leg raising (PLR) mimics an endogenous volume expansion (VE) that can be used to predict fluid responsiveness. This study was to assess the changes in stroke volume index (SVI) induced by PLR as an indicator of fluid responsiveness in mechanically ventilated patients with severe sepsis.

This was a prospective study. Thirty-two mechanically ventilated patients with severe sepsis were admitted for VE in ICU of the First Affiliated Hospital, Zhejiang University School of Medicine and Ningbo Medical Treatment Center Lihuili Hospital from May 2010 to December 2011. Patients with non-sinus rhythm or arrhythmia, parturients, and amputation of the lower limbs were excluded. Measurements of SVI were obtained in a semi-recumbent position (baseline) and during PLR by the technique of pulse indicator continuous cardiac output (PiCCO) system prior to VE. Measurements were repeated after VE (500 mL 6% hydroxyethyl starch infusion within 30 minutes) to classify patients as either volume responders or non-responders based on their changes in stroke volume index (ΔSVI) over 15%. Heart rate (HR), systolic artery blood pressure (ABPs), diastolic artery blood pressure (ABPd), mean arterial blood pressure (ABPm), mean central venous pressure (CVPm) and cardiac index (CI) were compared between the two groups. The changes of ABPs, ABPm, CVPm, and SVI after PLR and VE were compared with the indices at the baseline. The ROC curve was drawn to evaluate the value of ΔSVI and the change of CVPm (ΔCVPm) in predicting volume responsiveness. SPSS 17.0 software was used for statistical analysis.

Among the 32 patients, 22 were responders and 10 were non-responders. After PLR among the responders, some hemodynamic variables (including ABPs, ABPd, ABPm and CVPm) were significantly elevated (101.2±17.6 vs.118.6±23.7, P=0.03; 52.8±10.7 vs. 64.8±10.7, P=0.006; 68.3±11.7 vs. 81.9±14.4, P=0.008; 6.8±3.2 vs. 11.9±4.0, P=0.001). After PLR, the area under curve (AUC) and the ROC curve of ΔSVI and ΔCVPm for predicting the responsiveness after VE were 0.882±0.061 (95%CI 0.759-1.000) and 0.805±0.079 (95%CI 0.650-0.959) when the cut-off levels of ΔSVI and ΔCVPm were 8.8% and 12.7%, the sensitivities were 72.7% and 72.7%, and the specificities were 80% and 80%.

Changes in ΔSVI and ΔCVPm induced by PLR are accurate indices for predicting fluid responsiveness in mechanically ventilated patients with severe sepsis.