Factors predisposing to median sternotomy complications. Deep vs superficial infection.

STUDY OBJECTIVES Median sternotomy infections are a serious complication of cardiac surgery. The purpose of this study was to determine the patient characteristics and operative variables that predict incidence of sternal infection, and possibly its severity. DESIGN Univariate and multivariate retrospective analysis comparing patient, operative, and post-operative data in patients with and without sternal infections. SETTING Cardiac surgery program of a 580-bed private hospital in Toledo, Ohio. PATIENTS We studied 2,317 consecutive (June 1991 to December 1994) patients undergoing cardiac surgery. RESULTS Forty-one sternal infections were documented. Of these, 21 (0.91%) were deep infections with mediastinal involvement and 20 (0.86%) were superficial. Two patients with deep infections died (2/41, 5%). Ten variables were associated with infection by univariate analysis (p < 0.05), and of these, five were independent predictors by multivariate logistic regression. These predictors were obesity (p < 0.001), insulin-dependent diabetes (p < 0.001), use of internal mammary artery grafts (p = 0.02), surgical reexploration of the mediastinum (p = 0.003), and postoperative transfusions (p = 0.01). Predictors of deep and superficial sternal infection did not differ. Length of hospitalization was substantially longer for patients with deep (32 +/- 21 days) vs superficial infection (13 +/- 10 days). CONCLUSIONS The present study confirms previous findings that obesity, insulin-dependent diabetes, and internal mammary artery grafting (especially bilaterally) increase the risk of sternal infection. In addition, chest surgical reexploration and blood transfusions were postoperative factors that predisposed patients with median sternotomy to infection. Unlike their associated morbidity and mortality, predictors of deep and superficial sternal infections are similar.