OBJECTIVES. To investigate the epidemiology of surgical site infection in cardiac surgery patients operated on in 2006.

DESIGN. Retrospective study of a case-control sample.

SETTING. Cardiac surgery unit of a university teaching hospital in Hong Kong.

PATIENTS. Cardiac surgery patients with surgical site infection were matched by procedure type, sex, and year of surgery with non-infected patients.

MAIN OUTCOME MEASURES. Identification of risk factors for surgical site infection.

RESULTS. The infected and non-infected cardiac surgery patients did not differ in age, sex, or smoking history; however, patients with surgical site infection were significantly heavier (mean body mass index, 26.6 vs 23.9 kg/m²), P<0.046). Almost 41% of the subjects had a history of diabetes mellitus, there being a significantly greater proportion among infected than non-infected patients (53.1% vs 28.1%, P<0.042). All 37 of the patients without a diagnosis of diabetes had normal (ie <8 mmol/L) preoperative glucose levels, but 99% of them yielded evidence of subsequent glycaemic dysfunction during or after surgery. Overall, 50% of the patients had a blood transfusion during the operation, with infected patients significantly more likely to have been transfused than the non-infected ones (65.6% vs 34.4%, P<0.008).

CONCLUSIONS. There appears to be a relationship between surgical site infection in cardiac surgery patients and pre-existing (diagnosed and covert) diabetes mellitus and blood transfusion. Future studies should consider these factors in relation to surgical site infections, both in the wider surgical population and from a risk-minimisation perspective.

Key words: Blood transfusion; Cardiac surgical procedures; Diabetes mellitus; Risk factors; Surgical wound infection

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