Ultrasound Assessment of the Change in Carotid Corrected Flow Time in Fluid Responsiveness in Undifferentiated Shock

Objectives: Adequate assessment of fluid responsiveness in shock necessitates correct interpretation of hemodynamic changes induced by preload challenge. This study evaluates the accuracy of point-of-care Doppler ultrasound assessment of the change in carotid corrected flow time induced by a passive leg raise maneuver as a predictor of fluid responsiveness. Noninvasive cardiac output monitoring (NICOM, Cheetah Medical, Newton Center, MA) system based on a bioreactance method was used. Design: Prospective, noninterventional study. Setting: ICU at a large academic center. Patients: Patients with new, undifferentiated shock, and vasopressor requirements despite fluid resuscitation were included. Patients with significant cardiac disease and conditions that precluded adequate passive leg raising were excluded. Interventions: Carotid corrected flow time was measured via ultrasound before and after a passive leg raise maneuver. Predicted fluid responsiveness was defined as greater than 10% increase in stroke volume on noninvasive cardiac output monitoring following passive leg raise. Images and measurements were reanalyzed by a second, blinded physician. The accuracy of change in carotid corrected flow time to predict fluid responsiveness was evaluated using receiver operating characteristic analysis. Measurements and Main Results: Seventy-seven subjects were enrolled with 54 (70.1%) classified as fluid responders by noninvasive cardiac output monitoring. The average change in carotid corrected flow time after passive leg raise for fluid responders was 14.1 ± 18.7 ms versus –4.0 ± 8 ms for nonresponders (p

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