title: A prospective observational cohort study to identify the causes of anaemia and association with outcome in cardiac surgical patients.
abstract: OBJECTIVE
  Preoperative anaemia is associated with increased morbidity and mortality. We sought to determine the relative frequencies of the different causes of anaemia including absolute and functional iron deficiency, and the association of different haematological parameters, including plasma hepcidin, a key protein responsible for iron regulation, with outcomes after cardiac surgery.
  
  
  METHODS
  Prospective observational study between January 2012 and 2013; 200 anaemic cardiac surgical patients were recruited and 165 were studied. Detailed blood and bone marrow analysis was performed. Primary outcome was days alive and out of hospital.
  
  
  RESULTS
  Mean (SD) haemoglobin (Hb) was 102 (8) g/L for women and 112 (11) g/L for men. Regarding outcomes, 137 (83%) patients were transfused at least one unit of red blood cells; 30-day mortality was 1.8% (three patients). Functional iron deficiency was diagnosed in 78 patients (47%). Plasma hepcidin concentration was the only haematological variable associated with outcome, with mean days alive and out of hospital 2.7 (95% CI 0.4 to 5.1) days less if hepcidin ≥20 ng/mL compared with <20 ng/mL (p=0.024). Multivariable analysis showed that the association between hepcidin and outcome was independent of risk (European System for Cardiac Operative Risk Evaluation), transfusion and Hb.
  
  
  CONCLUSIONS
  Functional iron deficiency was the most common cause of anaemia but was not associated with outcome. The only haematological parameter that was associated with outcome was hepcidin concentration, which is a novel finding and introduces further complexity into our understanding of the role of iron and its regulation by hepcidin. We propose that future research should target patients with elevated hepcidin.
authors.affiliation: Department of Anaesthesia, Papworth Hospital, Cambridge, UK.
authors.forename: Matthew
authors.initials: M
authors.lastname: Hung
authors.affiliation: Department of Anaesthesia, Papworth Hospital, Cambridge, UK.
authors.forename: Erik
authors.initials: E
authors.lastname: Ortmann
authors.affiliation: Department of Haematology, Addenbrookes Hospital, Cambridge, UK.
authors.forename: Martin
authors.initials: M
authors.lastname: Besser
authors.affiliation: Department of Haematology, Addenbrookes Hospital, Cambridge, UK.
authors.forename: Pedro
authors.initials: P
authors.lastname: Martin-Cabrera
authors.affiliation: Division of Surgery and Interventional Science, University College London, London, UK.
authors.forename: Toby
authors.initials: T
authors.lastname: Richards
authors.affiliation: Department of Anaesthesia, Papworth Hospital, Cambridge, UK.
authors.forename: Marcus
authors.initials: M
authors.lastname: Ghosh
authors.affiliation: Department of Research and Development, Papworth Hospital, Cambridge, UK.
authors.forename: Fiona
authors.initials: F
authors.lastname: Bottrill
authors.affiliation: Department of Statistics, London School of Hygiene and Tropical Medicine, London, UK.
authors.forename: Timothy
authors.initials: T
authors.lastname: Collier
authors.affiliation: Department of Anaesthesia, Papworth Hospital, Cambridge, UK.
authors.forename: Andrew A
authors.initials: AA
authors.lastname: Klein
mesh_terms: D000368:Aged; D000740:Anemia / Q000097:blood / Q000453:epidemiology / Q000209:etiology / Q000628:therapy; D001803:Blood Transfusion / Q000379:methods; D001856:Bone Marrow Examination; D006348:Cardiac Surgical Procedures / Q000009:adverse effects / Q000379:methods / Q000401:mortality; D015331:Cohort Studies; D005260:Female; D006331:Heart Diseases / Q000601:surgery*; D006454:Hemoglobins / Q000032:analysis; D064451:Hepcidins / Q000032:analysis / Q000097:blood; D006801:Humans; D007501:Iron / Q000378:metabolism; D000090463:Iron Deficiencies; D008297:Male; D011183:Postoperative Complications / Q000453:epidemiology / Q000209:etiology; D011300:Preoperative Care / Q000379:methods; D012307:Risk Factors; D013223:Statistics as Topic; D006113:United Kingdom / Q000453:epidemiology
chemical_list: D006454:Hemoglobins; D064451:Hepcidins; D007501:Iron
keywords: CARDIAC SURGERY