[abstract] LACK OF MEASURABLE OXIDATIVE STRESS DURING HBO THERAPY IN BURN PATIENTS.

Abstract

It is well known that extended periods of hyperoxia causes oxidative lung injury. We used two markers, arterial plasma malondialdehyde (MDA) and expired breath hydrogen peroxide (EBH2O2) to evaluate the presence of oxidative stress during hyperbaric oxygen (HBO) therapy in 8 adult intubated patients treated for a variety of illnesses. 4 patients had smoke inhalation injury. All patients were treated with oxygen at 2 ATM for 90 minutes. Arterial blood and expired breath condensate were collected pre- and post-HBO treatment. MDA was measured spectrophotometrically as the thiobarbituate acid reactive adduct in plasma. H2O2 was measured spectrophotometrically by oxidation of 3,3^1,5,5^1 - tetramethylbenzidine with horseradish peroxidase and H2O2. In 8 patients 14 pre-and post-HBO determinations were made, 6.19 ± 3.02 & 6.07 ± 3.52 nmoles/ML respectively and 14 EBH2O2 pre-& post- HBO measurements, 1.07 ± 0.47 & 1.10 ± 0.65 micromoles, respectively. There were no statistically significant differentiation pre-& post- HBO in MDA & EBH2O2 values. In addition, there were no significant differences between either pre-HBO EBH2O2 or MDA levels in patients with smoke inhalation when compared to those without. Post HBO levels were also not significantly different between the two groups. We conclude that 90 minutes of HBO treatment does not lead to oxidative stress that can be measured by plasma MDA or EBH2O2. Conceivably, lung antioxidant defense mechanisms are not overwhelmed during 90 minutes of HBO and can contain the oxidative stress induced during that time period. In addition, lack of a significant pretreatment elevation of plasma MDA & EBH2O2 in smoke inhalation injuries suggests that oxidative stress may play a lesser role in the development of inhalational lung injury.