Risk Analysis of Deep Sternal Wound Infection and Mediastinitis in Cardiac Surgery

We read with interest the recent article by Gummert et al. on risk factor analysis of mediastinitis in cardiac surgery [1]. Based on a 1.44 % incidence of deep sternal wound infection (DSWI) in 9,303 patients undergoing cardiac surgery through full sternotomy, the group identifies use of one or two internal thoracic arteries (ITA) as bypass conduits, presence of diabetes, and increased body mass index (BMI) as significant independent perioperative risk factors for DSWI [1].

The Gummert report does not mention two recent reviews listing over 60 risk factors, including but not restricted to diabetes mellitus and ITA [2] [3]. They do not discuss the published conclusions of other investigators that multiple ITA bypasses can be performed without excessive morbidity, with low reoperation rates, and good long-term outcome [4]. Gummert's study suffers from a methodological problem common to research in this area - it concentrates on a limited number of DSWI risk factors, but does not consider all the risk factors reported in large groups of sternotomy patients [2] [3]. The modern understanding of DSWI lacks a validated concept of either the most significant risk factors or the most effective prevention guidelines for DSWI; recommendations have been typically based on theoretic rationales and suggestive evidence, with little resort to scientifically developed information [2] [3]. The Gummert study does little to improve this situation.

Gummert et al. do not list details of the particular type of sternotomy closure used in their series. They create an impression that sternal osteoporosis and suboptimal sternal closure were not considered among the risk factors influencing the DSWI incidence. The question of whether sternal instability or infection is the primary underlying problem in DSWI and mediastinitis remains unanswered. The recent literature suggests that closure stability can be improved by increasing the number of sternotomy wires [2]. Gummert et al. did not detail the technique of sternal debridement and reclosure during the course of mediastinitis, or whether this might have played a role in the 41 % mortality rate when mediastinal structures were revised more than twice [1]. A more stable mechanical fixation of the sternotomy, once dehiscence and mediastinitis occur, reduces the incidence of further complications [3] [5]. Gummert's study provides some insight into only a few of the known DSWI risk factors. Future studies in this problem should exhaustively consider and analyze the entire series of known risk factors described in the literature [2] [3] in order to evaluate possible cross-potentiations and help reduce the incidence of life-threatening DSWI.

References

• 1 Gummert J F, Barten M J, Hans C, Kluge M, Doll N, Walther T, Hentschel B, Schmitt D V, Mohr F W, Diegeler A. Mediastinitis and cardiac surgery - an updated risk factor analysis in 10,373 consecutive adult patients.  Thorac Cardiovasc Surg. 2002;  50 87-91
• 2 Losanoff J E, Jones J W, Richman B W. Primary closure of median sternotomy: techniques and principles.  Cardiovasc Surg. 2002;  10 102-110
• 3 Losanoff J E, Richman B W, Jones J W. Disruption and infection of median sternotomy: a comprehensive review.  Eur J Cardio-thorac Surg. 2002;  21 831-839
• 4 Jones J W, Schmidt S E, Miller R, Nahas C, Beall A C. Suitability and durability of multiple internal thoracic artery coronary artery bypasses.  Ann Surg. 1997;  225 785-791
• 5 Astudillo R, Vaage J, Myhre U, Karevold A, Garlund B. Fewer reoperations and shorter stay in the cardiac surgical ward when stabilizing the sternum with the Ley prosthesis in post-operative mediatinitis.  Eur J Cardio-thorac Surg. 2001;  20 133-139