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Crit Ultrasound J. 2017 Dec;9(1):10. doi: 10.1186/s13089-017-0065-0. Epub 2017 Apr 20.

Correlation of carotid blood flow and corrected carotid flow time with invasive cardiac output measurements.

Author information

1
Division of Emergency Ultrasound, Department of Emergency Medicine, Massachusetts General Hospital, 326 Cambridge Street, Suite 410, Boston, MA, 02114, USA. ima@ucalgary.ca.
2
Division of General Internal Medicine, Department of Medicine, University of Calgary, 3330 Hospital Dr NW, Calgary, AB, T2N 4N1, Canada. ima@ucalgary.ca.
3
Cardiology Division, Department of Medicine, Massachusetts General Hospital, 15 Parkman Street #800, Boston, MA, 02114, USA.
4
Division of Emergency Ultrasound, Department of Emergency Medicine, Massachusetts General Hospital, 326 Cambridge Street, Suite 410, Boston, MA, 02114, USA.
5
Department of Emergency Medicine, Hamad Medical Corporation, PO Box 3050, Doha, Qatar.
6
Department of Anaesthesia, Massachusetts General Hospital, 55 Fruit Street, Boston, MA, 02114, USA.
7
Department of Emergency Medicine, University Hospitals, Cleveland Medical Center, Case Western Reserve University, 11100 Euclid Ave, Cleveland, OH, 44106, USA.

Abstract

BACKGROUND:

Non-invasive measures that can accurately estimate cardiac output may help identify volume-responsive patients. This study seeks to compare two non-invasive measures (corrected carotid flow time and carotid blood flow) and their correlations with invasive reference measurements of cardiac output. Consenting adult patients (n = 51) at Massachusetts General Hospital cardiac catheterization laboratory undergoing right heart catheterization between February and April 2016 were included. Carotid ultrasound images were obtained concurrently with cardiac output measurements, obtained by the thermodilution method in the absence of severe tricuspid regurgitation and by the Fick oxygen method otherwise. Corrected carotid flow time was calculated as systole time/√cycle time. Carotid blood flow was calculated as π × (carotid diameter)2/4 × velocity time integral × heart rate. Measurements were obtained using a single carotid waveform and an average of three carotid waveforms for both measures.

RESULTS:

Single waveform measurements of corrected flow time did not correlate with cardiac output (ρ = 0.25, 95% CI -0.03 to 0.49, p = 0.08), but an average of three waveforms correlated significantly, although weakly (ρ = 0.29, 95% CI 0.02-0.53, p = 0.046). Carotid blood flow measurements correlated moderately with cardiac output regardless of if single waveform or an average of three waveforms were used: ρ = 0.44, 95% CI 0.18-0.63, p = 0.004, and ρ = 0.41, 95% CI 0.16-0.62, p = 0.004, respectively.

CONCLUSIONS:

Carotid blood flow may be a better marker of cardiac output and less subject to measurements issues than corrected carotid flow time.

KEYWORDS:

Cardiac output; Carotid blood flow; Carotid flow time; Carotid ultrasound

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