Non-invasive stroke volume measurement and passive leg raising predict volume responsiveness in medical ICU patients: an observational cohort study

INTRODUCTION: The assessment of volume responsiveness and the decision to administer a fluid bolus is a common dilemma facing physicians caring for critically ill patients. Static markers of cardiac preload are poor predictors of volume responsiveness, and dynamic markers are often limited by the presence of spontaneous respirations or cardiac arrhythmias. Passive leg raising (PLR) represents an endogenous volume challenge that can be used to predict fluid responsiveness. METHODS: Medical intensive care unit (ICU) patients requiring volume expansion were eligible for enrollment. Non-invasive measurements of stroke volume (SV) were obtained before and during PLR using a transthoracic Doppler ultrasound device prior to volume expansion. Measurements were then repeated following volume challenge to classify patients as either volume responders or non-responders based on their hemodynamic response to volume expansion. The change in SV from baseline during PLR was then compared with the change in SV with volume expansion to determine the ability of PLR in conjunction with SV measurement to predict volume responsiveness. RESULTS: A total of 102 fluid challenges in 89 patients were evaluated. In 47 of the 102 fluid challenges (46.1%), SV increased by ≥15% after volume infusion (responders). A SV increase induced by PLR of ≥15% predicted volume responsiveness with a sensitivity of 81%, specificity of 93%, positive predictive value of 91% and negative predictive value of 85%. CONCLUSIONS: Non-invasive SV measurement and PLR can predict fluid responsiveness in a broad population of medical ICU patients. Less than 50% of ICU patients given fluid boluses were volume responsive.