A critical review of the hemodynamics in assessment of volume responsiveness by using passive leg raising (PLR)

Background: The monitoring and regulation of cardiovascular function are increasingly based on dynamic indices. The aim of the present review is to scrutinize the history, physiological foundation, development, statistical apparatus and clinical impact on morbidity and mortality of one of the maneuvers leading to a dynamic index of fluid responsiveness, viz. the passive leg raising. Principal findings: Tracing the development of PLR from the early 80-ies revealed contrasting and irreconcilable perceptions of physiological mechanism in PLR and an increasing consensus on the formalities in analyzing results of validation studies in terms of ROC analysis, gray zones and Bayesian statistics resulting in the demonstration of good ability of PLR to predict volume responsiveness in an experimental setting. The impact on decreased morbidity and mortality, however, is absent in clinical trials involving PLR vs normal care. Conclusion: The passive leg raising manoeuvre is lacking in a consistent physiological modelling of the cardiovascular system, the purpose of the manoeuvre is ill-defined, the execution and timing are unclear and monitoring in the longer term leaves much to be desired. This serves to corroborate that the manoeuvre so far hasn't demonstrated a significant benefit in terms of survival in a clinical context. A call for an alternative approach is presented.