Findings of Brain Death with the Use of Carotid Duplex Ultrasonography

Abstract

Introduction Brain death is the complete and irreversible loss of cerebral and brain stem function. Although transcranial Doppler may be helpful in establishing the diagnosis, conventional carotid duplex ultrasound is not typically used in this condition. Case Report We describe the case of a 43-year-old woman with a past medical history of cardiac transplantation who was transferred from an outside hospital for hemodynamic monitoring and treatment. The patient had bladder surgery 1 day previously and suffered a prolonged cardiac arrest postoperatively. On arrival, she was comatose and ventilator dependent. Clinical examination revealed no brain stem reflexes (absent pupillary, corneal and oculocephalic reflexes). Brain death was suspected, although right upper-extremity flexion movements were noted. A carotid duplex ultrasound was ordered by the neurological service and performed using an Advanced Technology Laboratory HDI 5000 (Philips, Ultrasound, Bothell, Washington) machine with a linear 7–4 MHz transducer. Abnormal pulsed Doppler signals were detected demonstrating low velocity, bidirectional flow in the common and external carotid and the vertebral arteries. The internal carotid arteries demonstrated bizarre bidirectional and high resistive signals. Computed tomography showed diffuse cerebral edema and loss of gray-white matter differentiation. An electroencephalogram performed the next day demonstrated seizure activity correlating to her right upper extremity movements and indicative of some brain function retention. The patient died soon after. Conclusion Carotid duplex ultrasonography is not usually used in the diagnosis of brain death. Findings are characterized by a lack of diastolic flow or reverberating (to-and-fro pattern) flow and small systolic peaks in early systole on transcranial Doppler. This pattern is caused by a lack of adequate arterial perfusion. Cerebral angiography may reveal nonfilling of the intracranial arteries. Other diagnostic modalities, including computed tomography and electroen-cephalography, can be used with clinical findings to confirm brain death. In our case, carotid duplex ultrasonography was useful in assessing for brain death, although the patient (as later found) did not meet all neurological criteria. Vascular technologists should be aware of these unusual duplex findings in the evaluation of the comatose patient.