Survival Advantage and PaO2 Threshold in Severe Traumatic Brain Injury

Background: Hypoxemia can adversely affect outcome after traumatic brain injury (TBI). However, the effect of high PaO2 on TBI outcomes is controversial. The primary aim of this study was to identify the optimal PaO2 range early after severe TBI. Methods: In this single-center retrospective study conducted at a level-1 trauma center, patients with severe TBI (head Abbreviated Injury Scale score > 3, admission Glasgow Coma Scale score <= 8) were included. The crude and adjusted (including chest injuries and acute respiratory distress syndrome) effects of 50 mm Hg incremental PaO2 thresholds during the first 72 hours on discharge survival were examined. Results: Data from 193 patients (44 +/- 18 y; 77% male; admission Glasgow Coma Scale score 4 +/- 2) were reviewed. Overall survival was 57%. PaO2 thresholds in increments of 50 mm Hg between 250 and 486 mm Hg (68%) were associated with discharge survival in patients with severe TBI compared with PaO2 60 mm Hg < PaO2 < threshold. This association between PaO2 thresholds and survival was sustained until a PaO2 of 486 mm Hg (adjusted odds ratio 3.4; 95% confidence interval, 1.5-7.7). Although most patients had at least 1 PaO2 >= 250 mm Hg during the first 72 hours, in-hospital hypoxemia was common (24%) and was associated with mortality (survival adjusted odds ratio 0.46; 95% confidence interval, 0.22-0.95). Conclusions: In this series, a PaO2 threshold between 250 and 486 mm Hg during the first 72 hours after injury was associated with improved all-cause survival in patients with severe TBI, independent of hypocarbia or hypercarbia.