Objective:

To characterize temporal dynamics of systemic and pulmonary oxidative stress in patients with severe traumatic brain injury during the first 7 days and assess associations with arterial oxygenation parameters and clinical severity scores.

Approach:

• Study Design: Prospective observational cohort study.
• Setting: First-level trauma centre intensive care unit over 12 months.
• Participants: Forty mechanically ventilated adult patients with isolated severe brain injury.
• Interventions: No therapeutic intervention; standard intensive care management maintained.
• Outcome Measures: Concentrations of oxidative stress markers measured in serum and bronchoalveolar lavage fluid at three time points.

Key Findings:

• Antioxidant enzyme concentrations decreased progressively (p < 0.001), while oxidative damage markers increased.
• Lower PaO2 values were associated with higher 8-OHdG levels in serum (r = -0.64) and bronchoalveolar lavage fluid (r = -0.55).
• PaO2 was positively associated with antioxidant enzyme concentrations and serum MDA concentration.
• Early PaO2 values above 100 mmHg were associated with higher 28-day mortality in an unadjusted analysis (p < 0.05), but this finding requires cautious interpretation.

Interpretation:

Severe isolated brain injury is associated with progressive systemic and pulmonary oxidative stress, with a complex relationship between arterial oxygenation and oxidative stress.

Limitations:

• The exploratory study design limits causal inferences.
• Findings regarding PaO2 and mortality require cautious interpretation due to lack of support from fully adjusted models.

Conclusion:

The relationship between arterial oxygenation and oxidative stress may depend on timing and oxygen exposure levels.