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 (Stco2).
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 Stco2 (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 Stco2 with r = 0.8l and r2 = 0.66. Stco2 ≥75 was associated with CPP ≥ 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 Stco2 < 60, suggesting the potential of cerebral ischemia in the face of “normal” CPP. The Stco2 patches were user-friendly and not technically finicky.
Conclusion : In this pilot study, Stco2 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, Stco2 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.