Dose-dependent association of hyperoxia and decreased favorable outcomes in mechanically ventilated patients with traumatic brain injury, a retrospective cohort study.

Purpose: In patients with traumatic brain injury (TBI), adequate oxygenation is crucial to optimize survival and neurological outcome. However, supranormal oxygen partial pressure (PaO₂) only leads to minor increase in cerebral oxygen delivery but can cause numerous pathophysiological disturbances. Therefore, we aimed to study effects of hyperoxia on patient outcome and identify optimum PaO₂ ranges.

Methods: This retrospective, single-center cohort study included TBI patients receiving mechanical ventilation for ≥ 72 h. Time-weighted mean PaO₂ and integrals above thresholds of 80, 100, 120, and 150 mmHg were calculated over periods of 1, 3, 7, and 14 days. The effects on in-hospital mortality and favorable functional outcome defined as Glasgow Outcome Scale (GOS) ≥ 4 were explored at discharge and after 3-6 months.

Results: From 01/2013 until 12/2021, 290 patients fulfilled the inclusion criteria. Hyperoxia was dose-dependently associated with a worsened functional outcome 3-6 months post-injury. Regarding the first 24 h, odds ratios were 0.959 (95% confidence intervals: 0.932-0.990; p = 0.009) for time-weighted mean PaO₂ and 0.955 (0.923-0.988; p = 0.008), 0.939 (0.897-0.982; p = 0.006), 0.923 (0.871-0.978; p = 0.007) and 0.922 (0.858-0.992; p = 0.029) per mmHg above 80, 100, 120 and 150 mmHg, respectively. For exposure within 72 h, odds ratios were 0.897 (0.819-0.983; p = 0.020), 0.842 (0.738-0.961; p = 0.011) and 0.832 (0.705-0.981; p = 0.029) per mmHg per day over 100, 120 and 150 mmHg, respectively. No significant association could be established between PaO₂-exposure and in-hospital mortality, GOS at discharge or the 7- and 14-day periods.

Conclusion: In this cohort, hyperoxia within 72 h after admission was dose-dependently associated with an unfavorable neurological outcome after 3-6 months.