Passive leg raising for predicting fluid responsiveness: a systematic review and meta-analysis

We performed a systematic review and meta-analysis of studies investigating the passive leg raising (PLR)-induced changes in cardiac output (CO) and in arterial pulse pressure (PP) as predictors of fluid responsiveness in adults. MEDLINE, EMBASE and Cochrane Database were screened for relevant original and review articles. The meta-analysis determined the pooled area under the ROC curve, the sensitivity, specificity and threshold for the PLR test when assessed with CO and PP. Twenty-one studies (991 adult patients, 995 fluid challenges) were included. CO was measured by echocardiography in six studies, calibrated pulse contour analysis in six studies, bioreactance in four studies, oesophageal Doppler in three studies, transpulmonary thermodilution or pulmonary artery catheter in one study and suprasternal Doppler in one study. The pooled correlation between the PLR-induced and the fluid-induced changes in CO was 0.76 (0.73-0.80). For the PLR-induced changes in CO, the pooled sensitivity was 0.85 (0.81-0.88) and the pooled specificity was 0.91 (0.88-0.93). The area under the ROC curve was 0.95 +/- A 0.01. The best threshold was a PLR-induced increase in CO aeyen10 +/- A 2 %. For the PLR-induced changes in PP (8 studies, 432 fluid challenges), the pooled sensitivity was 0.56 (0.49-0.53), the pooled specificity was 0.83 (0.77-0.88) and the pooled area under the ROC curve was 0.77 +/- A 0.05. Sensitivity and subgroup analysis were consistent with the primary analysis. PLR-induced changes in CO very reliably predict the response of CO to volume expansion in adults with acute circulatory failure. When PLR effects are assessed by changes in PP, the specificity of the PLR test remains acceptable but its sensitivity is poor.