Brainstem auditory evoked potentials in toxic, metabolic and anoxic coma

The aim of this study was to evaluate the efficacy of brainstem auditory evoked responses as a prognostic tool in conditions of coma which interfere with cerebral metabolism. Thirteen patients in coma resulting from different systemic disorders (barbiturate intoxication, cardiac arrest, chronic hepatic insufficiency) were included in the study. Brainstem auditory evoked potentials were recorded and patients were graded according to the results. When used in conjunction with other clinical parameters (Glasgow Coma Scale), brainstem auditory evoked potentials provided a more reliable prognostic tool than the traditional EEG exam alone. A good correlation was found between electrophysiological data and clinical outcome not only in barbiturate (toxic) coma, but also in hepatic (metabolic) coma. Of particular significance was the disappearance of the components which follow wave III (grade 2), leading to a fatal outcome in all three patients in hepatic coma.