Prediction Of Neurological Outcome Using Bispectral Index In Patients With Severe Acute Brain Injury

ObjectiveTo establish a relation between the Bispectral Index (BIS) and other derivative parameter with the probability of consciousness recovery and outcome of the patients in a coma state due to severe acute brain injury.MethodsOne hundred and eighty-nine comatose brain-injured patients from whom sedative drugs were withdrawn at least24h before BIS recording were prospectively studied. BIS,95%spectral edge frequency (SEF), burst suppression ratio (SR), total power (TP), spontaneous electromyographic activity (EMG), and signal quality index (SQI) were recorded for30min. The neurologic condition of the patients was measured according to the Glasgow Coma Score (GCS) and Glasgow Outcome Score (GOS). Patients were followed up for assessment of consciousness recovery and outcome for30days after the injury. The studied variables were compared between the group of patients who recovered consciousness and those who did not by Mann-Whitney U test. Spearman’s correlation was used to model the relation between BIS derivative variables and patients’ neurological outcome, the area under receiver operating characteristic curve (AUC) of studied variables was used as an estimate of predictive ability of patients’ consciousness recovery and outcome.Results There were statistically significant differences between the group of patients who survived or recovered consciousness and those who did not, with respect to BIS, SR, TP, EMG, SQI, GCSBIS, APACHE Ⅱ and GOS at the30th day. The higher correlation coefficients for patients’ outcome at the30th day were0.738for GCSBIS,0.639for SR,0.591for BIS, and0.500for APACHE II, As to the patients’ consciousness recovery at the30th day, the higher correlation coefficients were0.656for GCSBIS,0.526for BIS,0.511for SR,0.491for APACHE Ⅱ. According to the area of receiver-operator characteristic curve, the better values to predict conscious and survival were GCSBISs, BIS, TP and EMG. The better parameters to predict unconscious were APACHE Ⅱ, SR and SQI. The better parameters to predict dead were SR, APACHE Ⅱ, SEF and SQI.ConclusionsThe study has demonstrated that BIS recording was related to and has a predictive ability of consciousness recovery and outcome in patients with severe acute brain injury, measured when the patients were without sedation.