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

Abstract

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 > or =15% after volume infusion (responders). A SV increase induced by PLR of > or =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.

Figure 1

Patient positioning during the four stages of measurement. After each change in position, two minutes elapsed before readings were recorded. The angle of elevation of the head or legs was 45 degrees. The patient's position was not changed between stages three and four.

Figure 2

Stroke volume change by stage for responders and non-responders. Each measurement is represented as a percent change from the measurement taken during stage one (* P < 0.001, Bonferonni adjusted level of significance 0.01). SV = stroke volume.

Figure 3

Individual percent change in stroke volume during passive leg raise for responders and non-responders. The dashed line represents the cutoff value of 15%. The squares represent the means with SD of the two groups (* P < 0.001, Bonferonni adjusted level of significance 0.01). PLR = passive leg raise; SV = stroke volume.

Figure 4

Receiver operating characteristic curves for predicting response to volume expansion. The dashed line represents the percent change in stroke volume (SV) during passive leg raise (PLR), the dotted line the stage one SV, and the solid line the stage one central venous pressure (CVP).

Figure 5

Bland-Altman plot of log-transformed difference against mean for paired stroke volume measurements from stages one and three. The dashed lines represent the log-transformed upper and lower limits of agreement (95% confidence interval for repeated measurements). SV = stroke volume.