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Crit Care Med. 2018 Nov;46(11):e1040-e1046. doi: 10.1097/CCM.0000000000003356.

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

Author information

1
Division of Pulmonary and Critical Care, Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA.
2
Department of Medicine, David Geffen School of Medicine at UCLA, Los Angeles, CA.
3
Medical School, David Geffen School of Medicine at UCLA, Los Angeles, CA.
4
UCLA Clinical and Translational Science Institute, David Geffen School of Medicine at UCLA, Los Angeles, CA.
5
Department of Health Policy and Management, Fielding School of Public Health at UCLA, Los Angeles, CA.
6
Department of Medicine Statistics, David Geffen School of Medicine at UCLA, Los Angeles, CA.
7
Division of Pulmonary and Critical Care, Department of Medicine, Weill Cornell Medical College, New York, NY.
8
Department of Anesthesiology, David Geffen School of Medicine at UCLA, Los Angeles, CA.

Abstract

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 < 0.001). Receiver operating characteristic analysis demonstrated that change in carotid corrected flow time is an accurate predictor of fluid responsiveness status (area under the curve, 0.88; 95% CI, 0.80-0.96) and a 7 ms increase in carotid corrected flow time post passive leg raise was shown to have a 97% positive predictive value and 82% accuracy in detecting fluid responsiveness using noninvasive cardiac output monitoring as a reference standard. Mechanical ventilation, respiratory rate, and high positive end-expiratory pressure had no significant impact on test performance. Post hoc blinded evaluation of bedside acquired measurements demonstrated agreement between evaluators.

CONCLUSIONS:

Change in carotid corrected flow time can predict fluid responsiveness status after a passive leg raise maneuver. Using point-of-care ultrasound to assess change in carotid corrected flow time is an acceptable and reproducible method for noninvasive identification of fluid responsiveness in critically ill patients with undifferentiated shock.

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