Correlation of noninvasive cerebral oximetry with cerebral perfusion in the severe head injured patient: A pilot study

Background: Traumatic brain injury (TBI) is a leading cause of morbidity and mortality in trauma patients. Cerebral perfusion pressure (CPP) directed ICU management is recommended for patients with severe TBI. It, however, requires an invasive device to measure intracranial pressure (ICP). Transcranial cerebral oximetry is a noninvasive method utilizing near-infrared technology to indirectly measure cerebral saturation (Stco(2)). Methods: A prospective observational study was performed at a Level I trauma center. Data were collected hourly for the first 6 days on four patients with severe TBI. Each patient had ICP monitoring and Stco(2) (INVOS, Somanetics) assessed from each frontal lobe. CPP directed care was used. Results: Four patients with TBI, with admission GCS scores of 4. 4. 7, and 8. all had subdural hematomas and contusions; three had subarachnoid hemorrhage (SAH); one had an epidural hematoma (the only death; day 6); two had craniotomies. In the first 48 hours when CPP 70, Stco2 was 71 +/- 9, while it was 61 9 when CPP < 70 (p < 0.0001). This relationship was constant for all study days, with p < 0.0001. Moreover, CPP < 70 correlated with Stco(2) with r = 0.81 and r(2) = 0.66. Stco(2) greater than or equal to75 was associated with CPP greater than or equal to 70 96.4% of the time (95% CL, 94.3-98.5%). Stco2 < 55 was associated with CPP < 70 68.2% of the time (95% CL, 57-79.4%). Also, 13.4% of observations with CPP ? 70 had Stco(2) < 60, suggesting the potential of cerebral ischemia in the face of ''normal'' CPP. The Stco(2) patches were user-friendly and not technically finicky. Conclusion: In this pilot study, Stco(2) correlated significantly with CPP. A Stco2 75 suggests that CPP is adequate, while < 55 suggests an inadequate CPP. Although these results should be confirmed in a larger study, Stco(2) may serve as a noninvasive measurement of cerebral perfusion in the patient with a TBI or, at the very least, a sensitive indicator for the need to begin monitoring the ICP.