title: Risk factors for mediastinitis following cardiac surgery: the importance of managing obesity.
abstract: BACKGROUND
  Mediastinitis is a devastating complication of cardiac surgery. Previous studies have often observed small populations, been retrospective in design, and used a variety of definitions for mediastinitis.
  
  
  OBJECTIVE
  To identify risk factors for mediastinitis, and strategies to minimize its incidence.
  
  
  METHODS
  A prospective cohort study of 4883 adult patients who underwent cardiac surgery between October 2003 and February 2009, comparing pre- and peri-operative risk factors, microbial aetiology, requirement for re-admission, length of stay and mortality between patients with and without mediastinitis.
  
  
  RESULTS
  Ninety (1.8%) patients were diagnosed with mediastinitis. Microbial aetiology was defined for 75 patients. Staphlyocococcus aureus was the most common isolate (30 episodes; 15 due to meticillin-resistant S. aureus). Univariate analysis revealed the following pre-operative factors associated with mediastinitis: age; body mass index; diabetes; modified logistic European System for Cardiac Operative Risk Evaluation score; urgent admission; and longer pre-operative stay (P < 0.05). Associated peri-operative factors were: combined coronary artery bypass grafting plus aortic valve replacement; longer aortic cross-clamp time; and longer cardiopulmonary bypass time (P < 0.005). Multi-variate analysis revealed that higher body mass index, combined coronary artery bypass grafting plus aortic valve replacement, and older age were associated with mediastinitis (P < 0.05). Mediastinitis was associated with re-admission to hospital, longer inpatient stay and reduced long-term survival (P < 0.05).
  
  
  CONCLUSIONS
  Mediastinitis is associated with worse short-term outcomes (re-admission, length of stay) and reduced long-term survival. Obesity is the only modifiable pre-operative risk factor for mediastinitis. It may be possible to reduce risk through pre-operative weight loss programmes before elective surgery.
authors.affiliation: Department of Cardiothoracic Surgery, John Radcliffe Hospital, Headington, Oxford, UK. Electronic address: mobyrehman@gmail.com.
authors.forename: S M
authors.initials: SM
authors.lastname: Rehman
authors.affiliation: Department of Cardiothoracic Surgery, John Radcliffe Hospital, Headington, Oxford, UK.
authors.forename: O
authors.initials: O
authors.lastname: Elzain
authors.affiliation: Department of Cardiothoracic Surgery, John Radcliffe Hospital, Headington, Oxford, UK.
authors.forename: J
authors.initials: J
authors.lastname: Mitchell
authors.affiliation: Department of Clinical Biochemistry, John Radcliffe Hospital, Headington, Oxford, UK.
authors.forename: B
authors.initials: B
authors.lastname: Shine
authors.affiliation: Department of Microbiology, John Radcliffe Hospital, Headington, Oxford, UK.
authors.forename: I C J W
authors.initials: IC
authors.lastname: Bowler
authors.affiliation: Department of Cardiothoracic Surgery, John Radcliffe Hospital, Headington, Oxford, UK.
authors.forename: R
authors.initials: R
authors.lastname: Sayeed
authors.affiliation: Department of Cardiothoracic Surgery, John Radcliffe Hospital, Headington, Oxford, UK.
authors.forename: S
authors.initials: S
authors.lastname: Westaby
authors.affiliation: Department of Cardiothoracic Surgery, John Radcliffe Hospital, Headington, Oxford, UK.
authors.forename: C
authors.initials: C
authors.lastname: Ratnatunga
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001424:Bacterial Infections / Q000382:microbiology; D001026:Coronary Artery Bypass / Q000009:adverse effects*; D005260:Female; D019918:Heart Valve Prosthesis Implantation / Q000009:adverse effects*; D006801:Humans; D008297:Male; D008480:Mediastinitis / Q000453:epidemiology / Q000209:etiology* / Q000382:microbiology; D008875:Middle Aged; D009765:Obesity / Q000150:complications*; D059035:Perioperative Period; D057234:Preoperative Period; D011446:Prospective Studies; D012307:Risk Factors; D055815:Young Adult
keywords: Cardiac surgery; Mediastinitis; Obesity