Introduction: The purpose of this study was to determine if noninvasive transcranial oxygen saturation (StcO2) 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 StcO2 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 StcO2 and BIS are associated with survival, good neurological outcome, ICP </=20, cerebral perfusion pressure (CPP) > or =60, and CAP index < or =0.30 (p < or = 0.001). Survival and good outcome are independently associated with BIS > or =60, StcO2 > or =70, and ICP < or =20 (p < 0.0001). BIS > or =60 or StcO2 > or =70 is associated with survival, good outcome, CPP > or =60, ICP < or =20, CAP index < or =0.30, and fewer ICP interventions (p < 0.0001). With BIS > or =60 or StcO2 > or =70, the rate of CPP > or =60 is 97.2% and the rate of ICP< or = 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 StcO2 are clinically relevant. The independent associations of BIS, StcO2, and ICP with outcomes suggest that noninvasive multi-modal monitoring may be beneficial. Future studies of patients with BIS > or =60 or StcO2 > or =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.