Comparing Changes in Carotid Flow Time and Stroke Volume Induced by Passive Leg Raising

Determining volume responsiveness in critically ill patients is challenging. We sought to determine if passive leg raise (PLR) induced changes in pulsed wave Doppler of the carotid artery flow time could predict fluid responsiveness in critically ill patients.

Medical intensive care unit patients ≥18 years old with a radial arterial line and FloTrac/Vigileo monitor in place were enrolled. Pulsed wave Doppler of the carotid artery was performed to measure the change in carotid flow time (CFT_C) in response to a PLR. Patients were categorized as fluid responders if stroke volume increased by ≥15% on a Vigileo monitor. The main outcome measure was the accuracy of CFT_C to detect a change in response to a PLR. We also calculated the percentage increase in CFT_C that could predict fluid responsiveness.

We enrolled 22 patients. Using an increase of ≥24.6% in the CFT_C in response to PLR to predict fluid responsiveness there was a sensitivity of 60%, specificity of 92%, positive likelihood ratio of 7.2, negative likelihood ratio of 0.4, positive predictive value of 86%, negative predictive value of 73% and receiver operating characteristic of 0.75 (95% CI: 0.54-0.96).

CFT_C performs well compared to stroke volume measurements on a Vigileo monitor. The use of CFT_C is highlighted in resource-limited environments and when time limits the use of other methods. CFTc should be validated in a larger study with more operators against a variety of hemodynamic monitors.