Reliability in diagnosis of brain death

Abstract

Objective: To compare some of the confirmatory investigations of brain death with clinical criteria in order to achieve the most sensitive and accurate diagnosis of brain death.

Design: All patients with isolated brain lesions and Glasgow Coma Scale (GCS) = 3 were subjected to neurological examination after ruling out hypothermia, metabolic disorders and drug intoxications and diagnosed as clinically brain-dead when the brainstem reflexes were absent and the apnea test positive.

Patients: 15 patients with clinical diagnosis of brain death entered this study.

Measurements and results: The patients were submitted to the following investigations: electroencephalogram (EEG), transcranial Doppler (TCD) of the middle cerebral arteries (MCA), cerebral blood flow measurements with the i.v. Xe-133 method (CBF) and selective cerebral angiography (CA). EEG was isoelectric in 8 patients while the remaining 7 patients showed persistence of electrical activity. TCD was compatible with intracranial circulatory arrest in 18 MCA districts, compatible with normal flow in 2 and undetectable in 10 out of 30 districts insonated. In CBF examinations, however, all the patients showed a characteristic "plateau" of the desaturation curves lasting through the whole investigation and suggestive of absent cortical flow. CA showed circulatory arrest in both carotid and vertebral arteries.

Conclusions: Our study suggests that cerebral angiography and CBF studies are the most reliable investigations whereas the role of EEG and TCD remains to be determined because of the presence of false negatives and positives.