Bispectral index monitoring for early detection of brain death

We sought to determine the utility of the bispectral index (BIS) as a tool for clinical evaluation of the moment of brain death (BD).

During a period of 12 months, 54 BDs were registered in our unit, of which 28 were included in the organ donation protocol; 24 fulfilled the requirements of our retrospective observational study. Continuous BIS monitoring was performed using an XP BIS monitor and BIS Quatro sensor evaluating the BIS and the suppression ratio (SR). In almost all cases, sonographic monitoring with transcranial Doppler ultrasound (TCD) was performed every 8 to 12 hours until the diagnosis of BD.

We detected a gradual decrease in BIS and increase in SR when the patients underwent clinical progression to BD. At the moment of BD diagnosis, all cases showed BIS 0 and SR 100. In 9 cases the follow-up TCD showed a BD pattern, moments before a BIS 0 and SR 100 appeared. In 18 cases, at the moment of BIS 0/SR 100, TCD showed BD. In all 24 cases, BD diagnosis was confirmed by means of neurological examination and electroencephalogram (EEG).

BIS monitoring is a continuous, simple method that is easy to interpret. It can help in clinical evolution and the decision of the BD moment. In our series, cerebral circulatory cessation (TCD) preceded BIS 0 and SR 100 values. The BIS prematurely detected the start of cerebral circulatory cessation, alerting us of BD.