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 (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.