Risk factors of infected sternal wounds versus sterile wound dehiscence

Sterile sternal dehiscence (SSD) and sternal wound infections (SWIs) are two complications of median sternotomy with high rates of morbidity. Sternal wound complications also carry significant economic burden, almost tripling patients' hospital costs and are considered a nonreimbursable "never event" for Medicare. Historically, SDD and SWI have been recognized as discrete entities, but nonetheless continue to be categorized as a singular complication in literature. The purpose of this study was to determine specific patient demographic and perioperative predictors of SSD and SWI.

An institutional review board-approved, retrospective study of 8098 consecutive patients who underwent cardiac surgery at Columbia University Medical Center between January 2008 and December 2013 was conducted. Patients were categorized into three groups: no sternal wound complication, SSD, or SWI. Statistical analysis was performed using univariate and multivariate logistic regression analysis.

Of 8098 patients, there were 73 patients (0.9%) with SSD and 40 (0.5%) with SWI who required plastic surgical consultation, debridement, and flap closure. In univariate analysis of SSD, positive predictors (i.e., "risk" factors) were age >42 years, prior surgery this admission, ≥2 arterial conduits, internal mammary artery (IMA) grafting with or without previous IMA grafting, body mass index (BMI) >30 (obese), CHF, diabetes requiring medication, respiratory failure, and unplanned cardiac reoperation; negative predictors (i.e., "protective" factors) were no arterial conduits and extubation within 24 h. In univariate analysis of SWI, positive predictors were IMA grafting with or without previous IMA grafting, postoperative hematocrit urgent/emergent surgical priority, BMI >30 (obese), cardiac ejection fraction <40%, and respiratory failure; negative predictors were no arterial conduits and elective surgical priority. In multivariate regression, BMI >30, diabetes requiring medication, and respiratory failure were determined to be significant positive predictors of SSD, and IMA grafting with or without prior IMA grafting and respiratory failure were significant positive predictors for SWI; no significant negative predictors were identified.

This study found that SSD and SWI have many common significant predictors consistent with findings that increased BMI, use of IMA grafts, poor cardiac reserve, and postoperative respiratory failure confer increased risk of sternal wound complications. Additionally, this study also found that there were predictors unique to each entity supporting that SSD and SWI may be related but are not a singular entity. Recognition and prevention of significant positive and negative predictors of SSD and SWI may be valuable in preoperative counseling, operative planning, and postoperative management. Although sternal wound complications can be successfully managed by plastic surgical intervention, preventing the development of median sternotomy complications may curb costs incurred by both patients and health care systems.