A Pilot Assessment of Carotid and Brachial Artery Blood Flow Estimation Using Ultrasound Doppler in Cardiac Surgery Patients

Objectives To estimate carotid and brachial artery blood flow with Doppler ultrasound in cardiac surgery patients and relate such estimates to cardiac index, lactate levels, and markers of renal function. Design A prospective observational study. Setting A teaching hospital. Participants Twenty-five elective cardiac surgery patients. Interventions The authors measured bilateral carotid and brachial artery blood flows using Doppler ultrasound and, simultaneously, cardiac index using a pulmonary artery catheter; lactate and serum creatinine levels; and urine output. The relationship between these indices and biomarkers was assessed statistically. Measurements and Main Results Median carotid arterial blood flow was estimated at 0.323 L/min (interquartile ratio [IQR], 0.256-0.429 L/min) on the right and 0.308 L/min (IQR, 0.247-0.376 L/min) on the left at baseline. Median brachial arterial blood flow was estimated at 0.063 L/min (IQR, 0.039-0.115 L/min) on the right and 0.063 L/min (IQR, 0.039-0.081 L/min) on the left at baseline. There was a weak correlation between right- and left-sided flows (brachial: rho = 0.285; carotid: rho = 0.384) and between brachial and carotid flow (right: rho = 0.135, left: rho = 0.225). There also was a weak correlation between cardiac index and brachial flow (right: rho = 0.215; left: rho = 0.320) and carotid flow (left: rho = 0.159) immediately after surgery, and no correlation 1 day after surgery (right brachial: rho = -0.010; left brachial: rho = -0.064; left carotid: rho = -0.060). There were no significant correlations between carotid or brachial flows and lactate and serum creatinine levels or urine output. Conclusions In cardiac surgery patients, Doppler-estimated carotid and brachial arterial blood flows have only a weak correlation with cardiac index and no correlation with lactate or creatinine levels or urine output. Thus, Doppler estimation of these blood flows cannot be used to provide noninvasive estimates of cardiac index in patients after cardiac surgery.