Carotid vs. aortic velocity time integral and peak velocity to predict fluid responsiveness in mechanically ventilated patients. A comparative study

Background: The carotid artery velocity-time integral (CVTI) and the carotid Doppler peak velocity (cDPV), as well as measures of their variation induced by the respiratory cycle, have been proposed as fast and easy to obtain ultrasound measures for assessing fluid responsiveness in intensive care unit patients. To investigate this possibility, we conducted a prospective observational study in hemodynamically unstable patients under mechanical ventilation. Methods: From May 1 to December 31, 2019, we conducted a prospective observational study involving 50 hemodynamically unstable patients under mechanical ventilation. We obtained a total of 800 Doppler ultrasound measurements from the left common carotid artery and at the level of the aortic annulus in the apical five-chamber view. The two measurements were performed before and after a 7 mL/kg fluid challenge and within the first hour of the onset of hemodynamic instability. The maximum Doppler peak velocity, the minimum Doppler peak velocity, and the maximum and minimum VTI at both the aortic and carotid level were acquired. Results: Twenty-eight (56%) patients showed a ≥15% increase in AoVTI after the fluid challenge, and were therefore identified as "fluid responders". All Doppler measurements were always significantly greater (P<0.0001) in fluid responders in relation to both carotid and aortic parameters. Good agreement between the above-mentioned measurements was found: Cohen's kappa coefficient between the carotid and aortic ΔDPV was 0.76 (95% CI 0.58-0.94); and between the Carotid and Aortic ΔVTI it was 0.84 (95% CI 0.68-0.99). Conclusions: CDPV was found to predict fluid responsiveness in unstable mechanically ventilated patients.