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 (PaO) 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 PaO ranges.

Methods: This retrospective, single-center cohort study included TBI patients receiving mechanical ventilation for ≥ 72 h. Time-weighted mean PaO 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 PaO 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 PaO-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.