title: Incidence and predictors of infection in patients undergoing primary isolated coronary artery bypass grafting: a report from a tertiary care hospital in a developing country.
abstract: OBJECTIVE
  Infection following coronary artery bypass grafting (CABG) is a leading cause of morbidity, mortality, and increased length of hospital stay. Many studies have investigated the predictive value of known risk factors for infection in patients following CABG and conclusions have been variable and may reveal regional or institution-specific influence. The purpose of this prospective study was to determine the pre- and peri-operative risk factors for infection in patients undergoing coronary artery bypass surgery in a developing country.
  
  
  METHODS
  A prospective study was undertaken to collect data on 12 reported risk factors for all patients undergoing CABG during a five-year period at The Aga Khan University Hospital, Pakistan. The relationship of these risk factors to infection following CABG was evaluated.
  
  
  RESULTS
  Out of 767 consecutive patients admitted for CABG, a total of 73 (9.51%) developed 92 infections following surgery. Sternal Surgical Site Infection (SSI) developed in 30 patients (3.91%), of which 29 (96.7%) were superficial and 1 (3.33%) was deep. There were 37 leg wound infections at the site of conduit harvest, and 2 cases of infection at the intra-aortic balloon pump. There were 12 cases of sepsis and 11 urinary tract infections. There were 26 cases (35.6%) of leukocytosis and 17 patients (23.3%) showed elevated erythrocyte sedimentation rate (ESR). Staphylococcus aureus was the most frequently isolated pathogen (39.7%). Bacteremia data was not collected. Of the total cases of infection following CABG, 59 required prolonged hospitalization or readmission. Univariate analysis was performed using a p-value of <0.2 as the inclusion criteria for further analysis using logistic regression. Multivariate analysis with adjusted Relative Risk (RR) showed that diabetes (P=0.002, RR=2.3, 95% CI=1.4-4.0), obesity (P=0.036, RR=2.2, 95% CI=1.0-4.4), use of an intra-aortic balloon pump (P=0.001, RR=3.6, 95% CI=1.7-7.7), female gender (P=0.004, RR=2.5, 95% CI=0.2-0.8) and prolonged mechanical ventilation (P=<0.0001, RR=6.7, 95% CI=2.8-15.5) were independent predictors of infection in the study population.
  
  
  CONCLUSIONS
  This study suggests that diabetes, obesity, use of an intra-aortic balloon pump and female gender are independent predictors of infection in patients undergoing CABG. Early and strict diabetic control and pre-operative weight reduction may reduce the incidence of infection following CABG. Contamination of these patients may occur before, during and after the operation and efforts to curb such contamination must be intensive. Further prospective studies need to be undertaken to identify and establish these and other risk factors for infection in the region and elsewhere.
authors.affiliation: Cardiothoracic Section, Department of Surgery, Aga Khan University Hospital, Karachi, Pakistan.
authors.forename: D
authors.initials: D
authors.lastname: Ahmed
authors.forename: F H
authors.initials: FH
authors.lastname: Cheema
authors.forename: Y I
authors.initials: YI
authors.lastname: Ahmed
authors.forename: K J
authors.initials: KJ
authors.lastname: Schaefle
authors.forename: S I
authors.initials: SI
authors.lastname: Azam
authors.forename: S A
authors.initials: SA
authors.lastname: Sami
authors.forename: H M
authors.initials: HM
authors.lastname: Sharif
mesh_terms: D016009:Chi-Square Distribution; D001026:Coronary Artery Bypass / Q000009:adverse effects*; D003906:Developing Countries / Q000706:statistics & numerical data*; D005260:Female; D006785:Hospitals, University / Q000706:statistics & numerical data*; D006801:Humans; D015994:Incidence; D016015:Logistic Models; D008297:Male; D010154:Pakistan; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D013249:Sternum / Q000601:surgery; D013530:Surgical Wound Infection / Q000453:epidemiology / Q000209:etiology* / Q000382:microbiology; D013997:Time Factors; D016896:Treatment Outcome