Reduction in incidence of deep sternal wound infections: random or real?

Comorbidities predisposing cardiac surgical patients toward deep sternal wound infection, such as diabetes and obesity, are rising in the United States. Longitudinal analysis of risk factors, morbidity, and mortality was performed to assessed effects of these health trends on deep sternal wound infection rates.

In this retrospective analysis of all median sternotomies performed at a single institution from 1991 through 2006, demographic and surgical characteristics were identified from a prospective database. The cohort was separated into periods from 1992 through 2001 and 2002 through 2006 to identify longitudinal trends in risk factors for deep sternal wound infection. Univariate and matched multivariable analyses were performed.

Overall, study population had increased comorbidities associated with deep sternal wound infection such as obesity, diabetes, and advanced age. Deep sternal wound infections were treated in 285 of 21,000 sternotomies performed during study period (1.35%). Deep sternal wound infection rates decreased from 1.57% to 0.88% in last 5 years. Rate of deep sternal wound infection was reduced among patients with diabetes from 3.2% to 1.0%. Multivariable analysis showed diabetes and smoking to be eliminated as risk factors in last 5 years. Prolonged bypass time was the only variable independently associated with deep sternal wound infection for the entire period. Thirty-day and 1-year mortalities for deep sternal wound infection did not change significantly.

Analysis of a large series of cardiac surgical patients demonstrates significant reduction in deep sternal wound infection incidence in 15 years. Introduction of perioperative intravenous insulin may explain some observed risk reduction. Efforts should focus on prevention, because mortality remains elevated.