Diagnosis of Absence of Cerebral Circulation by the Ultrasonic Doppler Method as a Confirmatory Test of Brain Death

Abstract

The usefulness of a non-invasive ultrasonic Doppler method in the diagnosis of absence of cerebral circulation under brain death was studied. The probe was placed over the bilateral internal carotid and vertebral arteries of 30 patients. Angiograms showed non-filling of cerebral vessels in 15 cases, and normal cerebral circulation in the other 15 control group patients. The blood flow patterns were monitored by an audible Doppler and recorded as sonograms (flow-velocity wave forms). In patients with normal circulation, the examination showed continuous one-way flow patterns. In the patients with angiographic non-filling patterns, a discontinuous bi-directional pattern was observed in all the vessels. The difference in sonographic patterns between these two groups was also distinguishable by auscultation of the Doppler sound patterns. In 4 cases, slow filling of the cerebral circulation by contrast medium was observed before the non-filling state developed. A low velocity continuous flow pattern with a weak reverse flow element was observed in all of them. Thus, an ultrasonic Doppler study can clearly diagnose the absence of cerebral circulation by studying the four major vessels in the neck and differentiate the absence of flow from a low cerebral blood flow state.