Is bispectral index monitoring an alternative method for diagnosis of brain death?

Introduction

EEG and cerebral angiography is usually mandatory beside clinical examination for the diagnosis of brain death. In recent years, for head trauma patients correlation was found between the Glasgow Coma Scale (GCS) and the bispectral index (BIS) that was dependent on the analysis of EEG. We studied whether BIS monitoring is an alternative method or not.

Materials and methods

Thirteen patients received in the ICU with deep coma between February 2004 and September 2004 were included in the study. GCS was ≤ 5 for all patients during ICU admittance. The reasons for coma were intracranial hemorrhagia, head trauma, cerebral anoxia. After the clinical diagnosis of brain death was made, all patients underwent EEG monitoring. Clinical inspection and EEG were made twice for 24 hours, BIS monitoring was performed for 2 hours after the detection of brain death.

Results

BIS values were 0 for 12 patients and 5 for one patient. Bioelectric silence was detected in all EEGs of all patients.

Discussion

BIS, which depends on bispectral analysis of EEG parameters, is used in the ICU for evaluation of sedation level. A meaningful correlation between neurologic status GCS and BIS has been reported for coma patients without sedation. Our findings are in line with these studies. BIS seems to be an alternative method for diagnosis of brain death with the advantage of easy application. However, EMG activity and cardiovascular hyperpulsatility may cause artifacts and false BIS evaluations. We believe that more studies are necessary for routine application of this new method.