Iron deficiency is associated with higher mortality in patients undergoing cardiac surgery: a prospective study

Background: Iron deficiency is frequent in patients undergoing cardiac surgery. The relevance of iron deficiency, however, is ill defined. Therefore, our study aimed to investigate the impact of iron deficiency (ferritin <100 mu g L-1) with or without concomitant anaemia on clinical outcome after cardiac surgery. Methods: In this prospective observational study, 730 patients undergoing elective cardiac surgery were assigned into four groups according to their iron status and anaemia. Mortality, serious adverse events (SAES), major cardiac and cerebrovascular events (MACCEs), allogenic blood transfusion requirements, and length of hospital stay were assessed during a 90-day follow-up period. The effect of iron deficiency on these outcomes was first calculated in models adjusting for anaemia only, followed by two multivariate models adjusting for anaemia and either the EuroSCORE II or any possible confounders. Results: The presence of iron deficiency (ferritin <100 mu g L-1) was associated with an increase in 90-day mortality from 2% to 5% in patients without anaemia, and from 4% to 14% in patients with anaemia. Logistic regression resulted in an odds ratio of 3.5 (95% confidence interval: 1.5-8.4); P=0.004. The effect persisted in both multivariate models. Moreover, iron deficiency was associated with an increased incidence of SAES, MACCEs, transfusion, and prolonged hospital stay. Conclusions: Preoperative iron deficiency (ferritin <100 mu g L-1) was independently associated with increased mortality, more SAES, and prolonged hospital stay after cardiac surgery. These findings underline the importance of preoperative iron deficiency screening in the context of a comprehensive patient blood management programme, and highlight its importance as a research topic in cardiac surgery.