Sternal wound complications--incidence, microbiology and risk factors.

OBJECTIVE: Sternal wound complications, i.e. instability and/or infection (mediastinitis), are important causes of morbidity in patients undergoing cardiac surgery via median sternotomy. Coagulase negative staphylococci, a normal inhabitant of the skin, have evolved as a cause of sternal wound infections. Since these opportunistic pathogens often are multiresistant, they can cause therapeutic problems.

METHODS: From 1980 through 1995 open heart surgery, was performed on 13,285 adult patients. Reoperation necessitated by sternal wound complications occurerd in 203 patients (1.5%). The incidence was 1.7% (168/9987) after coronary artery bypass grafting (CABG group) and 0.7% (35/3413) after heart valve surgery with or without concomitant CABG (HVR group).

RESULTS: Factors independently related to sternal complications in the CABG group (variable odds ratio [95% C.I.]): year of surgery, 1.9 [1.3-2.8] in 1990-1992, 2.0 [1.4-2.9] in 1993-1995; female sex, 0.4 [0.2-0.6]; diabetic disease, 1.8 [1.2-2.5]; bilateral ITA procedure, 3.3 [1.1-7.7]; and postoperative dialysis, 3.1 [1.4-6.9]. In the HVR group they were: use of ITA graft, 3.7 [1.7-7.7]; early re-exploration because of bleeding 3.0 [1.1-8.2]; and postoperative dialysis 3.1, [1.4-9.3]. Multivariate models were used to compute the risk for sternal complications in each patient. However, the prognostic models based on these risk scores provided low sensitivity and low predictive value. Patients with sternal wound complications showed no increased early mortality but worse long-term survival even after adjustment for other factors (relative hazard in CABG group 1.9 [1.2-2.8]; in HVR group 2.1 [1.1-4.3].

CONCLUSIONS: The use of ITA grafts seems to be one of the most important factors related to sternal wound complications. However, patients at truly increased risk for this complication could not be identified on the basis of the risk factors considered in this study.