Acute respiratory distress syndrome secondary to cardiopulmonary bypass: Do compromised plasma iron-binding antioxidant protection and thiol levels influence outcome?

Objectives: Cardiopulmonary bypass (CPB) surgery is often associated with m ild lung injury and in some patients leads to acute lung injury and acute r espiratory distress syndrome (ARDS), Aberrant plasma iron chemistry (increa sed iron loading of transferrin and/or the presence of redox-active low mol ecular mass iron) and increased plasma thiol levels are features of this ty pe of surgery and represent a potential pro-oxidant risk for oxidative dama ge. Oxidative damage is a feature of ARDS, and we hypothesized that pro-oxi dant forces may contribute to the onset and progression of ARDS. Design: Prospective, single center, observational study. Setting: University-affiliated tertiary referral cardiothoracic center. Patients: A total of 19 patients with ARDS secondary to CPB surgery and 64 patients with ARDS secondary to a variety of other predisposing causes. Interventions: Supportive techniques appropriate to the treatment of ARDS. Measurements and Main Results: Blood samples were collected into lithium he parin tubes for all patient groups on the first day of the admission of pat ients to the intensive care unit immediately after the diagnosis of ARDS. P lasma was immediately assayed for thiol content and total protein and album in levels. Plasma from patients with ARDS secondary to CPB surgery was also assayed for changes in iron chemistry. Nonsurviving patients with ARDS sec ondary to CPB surgery displayed significantly greater levels of aberrant ir on chemistry (elevated levels of iron saturation of transferrin) with decre ased iron-binding antioxidant protection and elevated plasma thiol levels t han did survivors. Plasma thiol levels in patients with ARDS secondary to o ther predisposing causes were (with the exception of lung-surgery patients) significantly elevated in survivors compared with those in nonsurvivors of the syndrome. Conclusions: Increased levels of plasma thiol appear to be associated with mortality in patients with ARDS secondary to CPB surgery.