The bispectral index, a useful adjunct for the timely diagnosis of brain death in the comatose trauma patient

Abstract

Background The bispectral index (BIS) is a processed electroencephalographic value (awake = 100, isoelectric = 0). The relationship of BIS and brain death (BD) is assessed. Methods BIS was evaluated in GCS 3 head-injured patients with BD (no brain function including apnea) or near BD (no apnea or negative ancillary test [cerebral perfusion and electroencephalogram]). Results In 27 patients, there were 37 BD evaluations (apnea assessment or ancillary test). BD was confirmed in 62% (n = 23). However, 38% (n = 14) showed near BD. BD BIS is 3 ± 5 and near BD BIS is 36 ± 31 ( P = .002). In the 23 BD patients, BIS was <20 for 7 hours ± 6 hours before a BD evaluation was performed. Of 14 near BD evaluations, 9 (64%) had BIS ≥20. BIS <20 for predicting BD had a sensitivity of 100% (23/23), a positive predictive value of 84% (23/28), and a negative predictive value of 100% (9/9). Conclusions Distinguishing brain death and near brain death in severely comatose trauma patients is complex. By indicating the likelihood of brain death, BIS is an adjunct for efficient evaluation.