The Incidence and Magnitude of Cerebral Desaturation in Traumatic Brain Injury: An Observational Cohort Study

Background: Cerebral ischemia in patients with traumatic brain injury (TBI) may propagate secondary neurological injury. Episodes of cerebral ischemia can be revealed through the use of cerebral oximetry monitoring. The objective of this study was to determine the incidence and severity of regional cerebral oxygen (rSO(2)) desaturation (rSO(2)<65%) in patients with severe TBI. Secondary outcomes included changes in other monitoring parameters associated with cerebral desaturation. Materials and Methods: In this single-center prospective observational cohort study, cerebral oximetry data were collected continuously for up to 72 hours in 18 adult patients with a diagnosis of severe nonpenetrating TBI who were being mechanically ventilated and undergoing intracranial pressure (ICP) monitoring an in intensive care unit in Canada. Mean arterial pressure (MAP), ICP, and cerebral perfusion pressure were collected at 5-minute intervals during the study period. Results: Twelve of 18 (67%) patients experienced an episode of cerebral desaturation. The median (interquartile range) nadir rSO(2) was 57% (51% to 62%). The duration of desaturation was 265 (57 to 1277) minutes or 8.1% (2.6% to 26.0%) of recording time. In all patients, a linear regression analysis of the area under threshold of 65% for rSO(2) was moderately correlated with the area above an ICP threshold of 20 mm Hg (R (2)=0.52; P<0.01). Similarly, there was a modest correlation between rSO(2) and MAP (R (2)=0.41; P<0.01). These relationships also held true for those patients who experienced cerebral desaturation. Patients having episodes of ICP >20 mm Hg were 6 times more likely to have a cerebral desaturation (relative risk: 6.0; 95% confidence interval: 1.3-34.7). Conclusions: Cerebral desaturations occur frequently in patients with severe TBI, and their duration can be protracted. Episodes of desaturation were moderately correlated with increased ICP and decreased MAP.