Transient iron overload with bleomycin detectable iron in the plasma of patients with adult respiratory distress syndrome.

BACKGROUND

A retrospective study was conducted to evaluate iron status in plasma samples collected from five patients with the adult respiratory distress syndrome (ARDS) who had bleomycin detectable iron in at least one sample. Ten patients with ARDS with no evidence of bleomycin detectable iron and 10 healthy individuals served as controls.

METHODS

Evidence of iron overload was established by measuring the percentage saturation of plasma transferrin. In each case the bleomycin assay for redox active, chelatable iron was used to measure plasma levels of non-transferrin bound iron in the low micromolar range; assays for total plasma iron and transferrin were performed to establish a diagnosis of transient iron overload. The effect of this on the ability of transferrin to act as a plasma antioxidant was assessed using two different assay systems.

RESULTS

The five patients with evidence of transient iron overload (mortality 4/5) represented 33% of the total population of patients with ARDS (mortality 5/10) managed by the unit during the study period. All had low molecular mass iron detectable in their plasma and had clinical and biochemical evidence of multiorgan system failure as well as liver impairment. Compared with the ARDS and normal control populations, transferrin and albumin levels were low and the former failed to act as a plasma antioxidant in preventing free radical mediated damage to detector molecules.

CONCLUSIONS

Patients with ARDS are thought to be under severe oxidative stress from their disease and from treatment with high inspired oxygen concentrations. A subgroup of patients with ARDS has been identified who displayed evidence of transient iron overload as a result of which their plasma iron binding antioxidant protection was greatly compromised. This finding must be considered a serious additional risk factor for oxidative stress.