Perioperative blood transfusion is predictive of poststernotomy surgical site infection: marker for morbidity or true immunosuppressant?

To analyze risk factors for the development of adult poststernotomy surgical site infections (SSIs), we performed a retrospective case-control study at a tertiary care hospital. Case patients with poststernotomy SSI between June 1999 and January 2001 were matched to control subjects without poststernotomy SSI according to date of procedure and age. Data were collected on known SSI risk factors. Of 711 procedures, we identified 38 cases with SSI and 114 matched controls. Univariate analysis revealed that receipt of transfused blood (odds ratio [OR], 3.19; 95% confidence interval [CI], 1.54-6.62), diabetes (OR, 2.90; 95% CI, 1.27-6.59), length of stay before hospitalization (OR, 1.19 per day; 95% CI, 1.02-1.37 per day), and American Society of Anesthesia score (OR, 2.19; 95% CI, 1.04-4.64) were significantly associated with SSI. Multivariate analysis revealed that transfusion (OR, 3.21; 95% CI, 1.41-7.31) and diabetes (OR, 3.65; 95% CI, 1.42-9.36) were predictors for SSI. The exact role of blood transfusion in the pathogenesis of SSI, whether as a direct immunosuppressant or a surrogate marker for morbidity, remains unresolved.