Severe brain injury ICU outcomes are associated with Cranial-Arterial Pressure Index and noninvasive Bispectral Index and transcranial oxygen saturation: a prospective, preliminary study

INTRODUCTION: The purpose of this study was to determine if noninvasive transcranial oxygen saturation (StcO(2)) and Bispectral Index (BIS) correlate with severe traumatic brain injury intensive care unit (ICU) outcomes. METHODS: This is a prospective observational study. Values of intracranial pressure (ICP), mean arterial pressure (MAP), BIS, and StcO(2 )were recorded hourly for the first six, post-injury days in 18 patients with severe brain injury. Included in the analyses was the Cranial-Arterial Pressure (CAP) Index, which is ICP/(MAP - ICP). RESULTS: After 1,883 hours of data were analyzed, we found that StcO(2 )and BIS are associated with survival, good neurological outcome, ICP ≤20, cerebral perfusion pressure (CPP) ≥60, and CAP index ≤0.30 (p ≤ 0.001). Survival and good outcome are independently associated with BIS ≥60, StcO(2 )≥70, and ICP ≤20 (p < 0.0001). BIS ≥60 or StcO(2 )≥70 is associated with survival, good outcome, CPP ≥60, ICP ≤20, CAP index ≤0.30, and fewer ICP interventions (p < 0.0001). With BIS ≥60 or StcO(2 )≥70, the rate of CPP ≥60 is 97.2% and the rate of ICP≤ 25 is 97.1%. An increased CAP index is associated with death, poor neurological outcome, and increased ICP interventions (p < 0.0001). With CAP index >0.25, MAP is not related to ICP (p = 0.16). CONCLUSION: Numerous significant associations with ICU outcomes indicate that BIS and StcO(2 )are clinically relevant. The independent associations of BIS, StcO(2), and ICP with outcomes suggest that noninvasive multi-modal monitoring may be beneficial. Future studies of patients with BIS ≥60 or StcO(2 )≥70 will determine if select patients can be managed without ICP monitoring and whether marginal ICP can be observed. An increased CAP index is associated with poor outcome.