The reliability of carotid ultrasound in determining the return of pulsatile flow: A pilot study

Manual palpation of pulses is unreliable in detecting pulsatile flow in human participants, complicating the assessment of return of spontaneous circulation after cardiac arrest. Ultrasound may offer an alternative. This study's objective was to investigate whether return of pulsatile flow in humans can be reliably assessed by common carotid artery ultrasound. We conducted a single-blinded randomised study of common carotid artery ultrasound using 20 cardiopulmonary bypass patients to model the return of pulsatile flow. Synchronised time-stamped videos of radial artery invasive blood pressure and 10 two-dimensional or 10 colour Doppler ultrasounds were recorded. Three independent reviewers recorded the timestamp where they considered pulsatile flow was first visible on ultrasound. Ultrasound times were compared to the onset of arterial line pulsatile flow and reliability assessed by intraclass correlation coefficient. The median difference between radial artery and ultrasound flow time (interquartile range (range)) was 24 seconds (5-40 (0-93)) for two-dimensional and 5 seconds (2-17 (-28 to 188)) for colour Doppler. The intraclass correlation coefficient for two-dimensional ultrasound was 0.86 (95%CI 0.63-0.96) and 0.32 (95%CI -0.01 to 0.71) for colour Doppler. The median (interquartile range (range)) mean arterial pressure where ultrasound flow occurred for two-dimensional ultrasound was 62 mmHg (49-74 (33-82)) and 56 mmHg (52-73 (43-83)) for colour Doppler. In our pilot study, two-dimensional ultrasound was reliable in detecting the return of pulsatile flow. Colour Doppler detected pulsatile flow earlier and at lower mean arterial pressure but was not reliable, although a larger study is needed to determine colour Doppler's utility.