BACKGROUND
In several lung diseases, oxidative stress can be demonstrated. This has not been shown in patients with ventilator-associated pneumonia (VAP).

METHODS
We studied plasma and bronchoalveolar lavage (BAL) samples for markers of oxidative stress, taken from patients with VAP. Seventy-eight patients likely to have VAP and 10 patients who were not suspected of having VAP were studied prospectively. A diagnosis of VAP was based on a positive quantitative mini-lavage culture of > or = 10(3) colony-forming units per ml. Blood and BAL samples were collected and analysed for thiobarbituric acid reactant substances (TBARS) and antioxidant activity.

RESULTS
Plasma and alveolar TBARS increased significantly in patients who developed VAP compared with those who did not, by 43% and 259% respectively. Red cells and alveolar glutathione peroxidase concentrations (antioxidant activity) were lower in those with VAP compared with the non-VAP group, by 43% and 68% respectively. No significant differences were found for serum superoxide dismutase activity. Significant differences were found for alveolar glutathione peroxidase concentrations over time in the VAP group. No significant differences between survivors and non-survivors were found in the blood or BAL assays, in patients with VAP.

CONCLUSIONS
VAP is associated with evidence of early oxidative stress in the alveolar fluid and blood.