The effects of hyperoxia on the neurological outcomes of patients with severe traumatic brain injury (TBI) are still controversial. We examined whether the partial pressure of arterial oxygen (PaO2) and hyperoxia were associated with neurological outcomes and survival by conducting post-hoc analyses of the Brain Hypothermia (B-HYPO) study, a multi-center randomized controlled trial of mild therapeutic hypothermia for severe TBI. The differences in PaO2 and PaO2/fraction of inspiratory oxygen (P/F) ratio on the 1st day of admission were compared between patients with favorable (n = 64) and unfavorable (n = 65) neurological outcomes and between survivors (n = 90) and deceased patients (n = 39). PaO2 and the P/F ratio were significantly greater in patients with favorable outcomes than in patients with unfavorable neurological outcomes (PaO2: 252 ± 122 vs. 202 ± 87 mm Hg, respectively, p = 0.008; P/F ratio: 455 ± 171 vs. 389 ± 155, respectively, p = 0.022) and in survivors than in deceased patients (PaO2: 242 ± 117 vs. 193 ± 75 mm Hg, respectively, p = 0.005; P/F ratio: 445 ± 171 vs. 370 ± 141, respectively, p = 0.018). Similar tendencies were observed in subgroup analyses in patients with fever control and therapeutic hypothermia, and in patients with an evacuated mass or other lesions (unevacuated lesions). PaO2 was independently associated with survival (odds ratio 1.008, p = 0.037). These results suggested that early-stage hyperoxia might be associated with favorable neurological outcomes and survival following severe TBI.
Keywords: P/F ratio; PaO2; TBI; hyperoxia.