title: Latitude of the study place and age of the patient are associated with incidence of mediastinitis and microbiology in open-heart surgery: a systematic review and meta-analysis.
abstract: OBJECTIVE
  We aimed to summarize the pooled frequency of mediastinitis following open-heart surgery caused by Gram-positive bacteria, including methicillin-resistant Staphylococcus aureus (MRSA), and Gram-negative bacteria.
  
  
  METHODS
  This study was a systematic review and a meta-analysis of prospective and retrospective cohort studies.
  
  
  METHODS
  We searched the literature, and a total of 97 cohort studies were identified. Random-effect model was used to synthesize the results. Heterogeneity between studies was examined by subgroup and meta-regression analyses, considering study and patient-level variables. Small-study effect was evaluated.
  
  
  RESULTS
  Substantial heterogeneity was present. The estimated incidence of mediastinitis evaluated from 97 studies was 1.58% (95% confidence intervals [CI] 1.42, 1.75) and that of Gram-positive bacteria, Gram-negative bacteria, and MRSA bacteria evaluated from 63 studies was 0.90% (95% CI 0.81, 1.21), 0.24% (95% CI 0.18, 0.32), and 0.08% (95% CI 0.05, 0.12), respectively. A meta-regression pinpointed negative association between the frequency of mediastinitis and latitude of study place and positive association between the frequency of mediastinitis and the age of the patient at operation. Multivariate meta-regression showed that prospective cohort design and age of the patients and latitude of study place together or in combination accounted for 17% of heterogeneity for end point frequency of mediastinitis, 16.3% for Gram-positive bacteria, 14.7% for Gram-negative bacteria, and 23.3% for MRSA bacteria.
  
  
  CONCLUSIONS
  Evidence from this study suggests the importance of latitude of study place and advanced age as risk factors of mediastinitis. Latitude is a marker of thermally regulated bacterial virulence and other local surgical practice. There is concern of increasing risk of mediastinitis and of MRSA in elderly patients undergoing sternotomy.
authors.affiliation: Centre for Clinical Heart Research, Department of Cardiology, Oslo University Hospital, Oslo, Norway; Oslo Centre for Biostatistics and Epidemiology, Oslo University Hospital, Oslo, Norway.
authors.forename: M
authors.initials: M
authors.lastname: Abdelnoor
authors.affiliation: Department of Cardiovascular Surgery, Oslo University Hospital, Oslo, Norway.
authors.forename: Ø A
authors.initials: ØA
authors.lastname: Vengen
authors.affiliation: Department of Cardiology, Oslo University Hospital, Oslo, Norway.
authors.forename: O
authors.initials: O
authors.lastname: Johansen
authors.affiliation: Oslo Centre for Biostatistics and Epidemiology, Oslo University Hospital, Oslo, Norway.
authors.forename: I
authors.initials: I
authors.lastname: Sandven
authors.affiliation: Department of Experimental Pathology, Immunology and Microbiology, American University of Beirut, Beirut, Lebanon.
authors.forename: A M
authors.initials: AM
authors.lastname: Abdelnoor
keywords: mediastinitis; meta-analysis; sternotomy