Evidence Corner: Sternal Incision Infections

Dear Readers:   Coronary artery bypass grafting (CABG) saves lives and is a preferred treatment option for acute coronary artery symptoms resulting from arterial obstruction.¹ Surgical site infections (SSI) occur in 2%–20% of patients within 30–60 days after CABG surgery with 0.5%–5% categorized as more serious deep sternal wound infections (DSWI), including mediastinitis.² Considerable research has been devoted to identifying risk factors for these SSI and minimizing their likelihood. The two studies reviewed in this edition of Evidence Corner highlight the economic impact of SSI following CABG surgery. One offers a simple intervention to decrease their incidence. Laura Bolton, PhD, FAPWCA Adjunct Associate Professor Department of Surgery, UMDNJ WOUNDS Editorial Advisory Board Member and Department Editor

Deep Sternal Wound Infections

  Reference: Graf K, Ott E, Vonberg RP, Kuehn C, Haverich A, Chaberny IF. Economic aspects of deep sternal wound infections. Eur J Cardiothorac Surg. 2010;37(4):893–896.   Rationale: Deep sternal wound infections (DSWI) can complicate CABG surgery, potentially increasing related costs and extending the length of stays in hospitals (LOS) and intensive care units (ICU).   Objective: Determine the length of hospital and ICU stay and total costs of care for patients undergoing CABG who do or do not experience a postsurgical DSWI.   Methods: Between January 2006 and March 2008, a case-control study compared total costs of care for patients undergoing CABG surgery versus without a DSWI in an acute care hospital in Germany. DSWI patients (n = 17) were included if they met Centers for Disease Control and Prevention (CDC) criteria for developing a DSWI during the hospital stay after CABG surgery. For each DSWI patient, two control patients (n = 34) with no signs or symptoms of DSWI during the postoperative hospital stay were matched on important SSI risk variables including surgery diagnosis-related group, age (± 5 years), gender, and duration of hospital stay before surgery (± 2 days). Each control patient had at least as long a period of being at risk for infection as the matched patient with a DSWI. Outcomes measured were median costs of a CABG case, LOS, and length of ICU stay.   Results: Median overall costs of a CABG case with DSWI was €36,261 ($51,246) compared to €13,356 ($18,875) without a DSWI (P P = 0.0006). DSWI added 1 day to the normal median 5.3-day ICU stay for a CABG patient.   Authors’ Conclusions: DSWI represent an important economic factor for hospitals managing patients undergoing CABG surgery. Appropriate infection control measures to prevent DSWI are recommended.

Hydrocolloid Dressings Prevent CABG Surgical Site Infection

  Reference: Teshima H, Kawano H, Kashikie H, et al. A new hydrocolloid dressing prevents surgical site infection of median sternotomy wounds. Surg Today. 2009;39(10):848–854.   Rationale: CDC guidelines recommend covering surgical wounds for 24–48 hours, but covering wounds after this interval is not discussed resulting in varied practice. Hydrocolloid dressings (HCD) may perform well as a post-surgical dressing because they maintain a moist environment and protect from secondary infection.   Objective: Compare incidence and costs of SSI in patients undergoing CABG surgery whose median sternotomy wounds were dressed with an occlusive HCD or a polyurethane foam-film dressing (PFD) in an acute care hospital in Japan.   Methods: A cohort of 253 consecutive patients undergoing CABG surgery between January 2002 and December 2005 were assigned to be dressed with either a HCD (n = 117) or a PFD (n = 136) on each full-length median sternotomy incision. Surgery was standardized, as was fascia or subcutaneous tissue closure with interrupted non-resorbable nylon and final skin closure with staples. HCD, randomly assigned for use by younger surgeons, were left in place for the first 7 postoperative days (POD). PFDs, randomly assigned for use by senior surgeons, were removed after 48 hours according to CDC guidelines, allowing wound evaluation and then replaced with an occlusive adhesive wound dressing left in place until POD 7, after which both groups received the occlusive adhesive follow-up dressing as needed until completion of treatment. Dressing integrity and wound infection signs were checked daily through the translucent HCD and to the extent possible with the PFD dressing left in place unless changed per protocol. Outcomes measured included dressing cost, mortality, and SSI graded according to CDC criteria as either superficial (involving skin and/or subcutaneous tissue) or deep (DSWI involving muscle and/or bone). SSI treatment consisted of intravenous antibiotics bactericidal to organisms cultured from the SSI, given until the chest and pericardial tubes were removed. All patients were followed up by interview 2 weeks, 3 months, and 1 year after surgery. SSI risk factors were determined using univariate and multivariate logistic regression analysis.   Results: HCD and PFD groups did not differ in preoperative or in perioperative profiles except for longer aortic cross-clamp and extracorporeal circulation times for the HCD group. There were fewer SSI (P P 2, chronic obstructive pulmonary disease, insulin-dependent Type 2 diabetes mellitus and bilateral internal thoracic artery involvement.   Authors’ Conclusions: This study clearly demonstrated effectiveness of the new HCD as a cost effective sternotomy incision dressing preventing SSI even when bilateral internal thoracic arteries were involved.

Clinical Perspective

  Highly skilled coronary artery bypass surgery would seem to call for an optimal wound environment to prevent bacteria from undoing the surgeon’s work. These two studies confirm the economic burden that a deep or a shallow SSI adds a significant economic and clinical burden to CABG surgery. The Japan study suggests that HCD dressings in situ for 7 days may reduce the likelihood of post-CABG SSI. Teshima et al point out that their results highlight the HCD as a potential advance in surgical dressing interventions rather than suggesting a deficiency of PFD, which have proven safe and effective as a widely used postoperative dressing, changed every 24–48 hours. The contribution of surgical experience to this result remains to be explored.   Whether this striking reduction of SSI results from less frequent wound exposure to the environment or to HCD capacity to seal out microorganisms and seal in healing molecules and fluids remains to be tested in future studies. The required PFD dressing change 48 hours after surgery in the Japan study may have exposed the sternotomy incisions to exogenous organisms at a time when they were highly susceptible to microbial invasion. Teshima et al reported that unlike the nearly transparent HCD, changing the PFD was necessary on POD 2 to allow wound evaluation and because the PFD became soiled.   Prior research on cardiothoracic surgery patients in Australia3 reported no DSWI in thin HCD-dressed (n = 267) sternotomy wounds compared to 2% each in groups dressed with a transparent film (n = 227) or a dry absorbent (n = 243) dressing (P = 0.0536). A similar study in The Netherlands⁴ showed no SSI advantage of a transparent film dressing (2.6% SSI) compared to a water- and air-permeable absorbent dressing (3.3% SSI) both changed on postoperative day 2. Mertz et al⁵ reported that HCD protected wounds from S aureus and P aeruginosa in a swine wound model where both organisms reached the wound through the transparent film dressing within 24–48 hours.   HCD sealing capacity may contribute importantly to wound protection, preventing SSI. Growing evidence suggests HCD use in preventing acute and chronic wound infections.^5,6 It may be time to explore the importance of HCD and/or changing surgical dressings less frequently in helping to prevent SSI, particularly as one can evaluate clinical signs and symptoms of SSI without removing a thin HCD.

References

1. Eagle KA, Guyton RA, Davidoff R, et al. ACC/AHA 2004 guideline update for coronary artery bypass graft surgery: a report of the American College of Cardiology/American Heart Association Task Force on Practice Guidelines (Committee to Update the 1999 Guidelines for Coronary Artery Bypass Graft Surgery). Circulation. 2004;110(14):e340–e437. 2. Swenne CL, Lindholm C, Borowiec J, Carlsson M. Surgical-site infections within 60 days of coronary artery by-pass graft surgery. J Hosp Infect. 2004;57(1):14–24. 3. Wynne R, Botti M, Stedman H, et al. Effect of three wound dressings on infection, healing comfort, and cost in patients with sternotomy wounds: a randomized trial. Chest. 2004;125(1):43–49. 4. Segers P, de Jong AP, Spanjaard L, Ubbink DT, de Mol BA. Randomized clinical trial comparing two options for postoperative incisional care to prevent poststernotomy surgical site infections. Wound Repair Regen. 2007;15(2):192–196. 5. Mertz PM, Marshall DA, Eaglstein WH. Occlusive wound dressings to prevent bacterial invasion and wound infection. J Am Acad Dermatol. 1985;12(4):662–668. 6. Hutchinson JJ, McGuckin M. Occlusive dressings: a microbiologic and clinical review. Am J Infect Control. 1990;18(4):257–268. 7. Wiechula R. The use of moist wound-healing dressings in the management of split-thickness skin graft donor sites: a systematic review. Int J Nurs Pract. 2003;9(2):S9–S17.