Lack of association between carotid artery volume blood flow and cardiac output

Objective. The correlation of cardiac output and cerebral perfusion is uncl ear. We tested this potential association by correlating cardiac output dat a obtained by echocardiography and cerebral blood flow data as determined b y color M-mode measurements of carotid artery blood flow. Methods. We studi ed 43 patients with a broad spectrum of cardiac performance by means of tra nsthoracic echocardiography. in these patients, different cardiac indices s uch as stroke volume, ejection fraction, and heart minute volume were deter mined. The data were correlated with volumetric flow measurements (color M- mode duplex system) of the common carotid arteries bilaterally. Results. He art minute volume ranged from 1.632 to 9.836 mL/min (mean SD, 4.652 +/- 1.6 21 mL/min); ejection fraction ranged from 18% to 76% (mean, 48% +/- 16%). T he relative fraction of carotid volume flow compared with heart minute volu me was 15% +/- 6%. There was no correlation between ejection fraction, stro ke volume, or heart minute volume and absolute volume flow in the carotid a rteries when being adjusted for age. There was a highly significant inverse correlation (r = -0.8; P < .0001) of the relative fraction of the carotid volume flow (carotid volume flow/heart minute volume [percent]) and the hea rt minute volume. Conclusion. Our data support the concept that cerebral bl ood flow is independent of cardiac output.