Prevention of poststernotomy wound infections in obese patients by negative pressure wound therapy

Objective: Patients who develop sternal wound infections (SWI) following median sternotomy experience worse clinical outcomes and require longer and more costly care than patients without this complication. The majority of SWI in obese patients are triggered by the breakdown of skin sutures and subsequent seepage of skin flora. The purpose of this study was to evaluate negative pressure wound dressing treatment (NPWT) for the prevention of SWI. We hypothesized that NPWT for 6 – 7 days applied immediately after skin closure reduces the numbers of wound infections by skin flora.

Methods: In a prospective study 177 consecutive obese patients (BMI ≥30) with cardiac surgery performed via median sternotomy were analyzed. In the NPWT group (n = 102) a foam dressing (Prevena™, KCI, Wiesbaden, Germany; therapy costs: 350€/patient) was placed immediately after skin suturing and negative pressure of -125 mmHg was applied for 6 to 7 days. In the control group (n = 75) conventional wound dressings were used. Primary endpoint was wound infection within 90 days. Wound infections were defined on the basis of the criteria of the US Centers for Disease Control and Prevention (CDC). Mann-Whitney U-test and Fisher's exact test were used.

Results: Preoperative patient characteristics, comorbidities, SWI risk factors and procedure-related variables were comparable between NPWT group and control group (all p>.05). Four out of 102 (3.9%) patients with continuous NPWT suffered from wound infections compared to 12 out of 75 (16%) patients with conventional sterile wound dressing (p < 0.02). Wound infections with Gram positive skin flora were found in only one patient in the NPWT group compared to 10 patients in the control group (p < 0.01). Patients with SWI (n = 16) had to be treated by surgical debridement and secondary wound closure or by repeated revisions, including VAC therapy, resulting in an extended median overall length of hospital stay (32.5 d vs. 15.5 d) and additional therapy costs of about 9.000€ per case.

Conclusions: Negative pressure wound therapy (NPWT) over clean, closed incisions for the first 6 to 7 postoperative days significantly reduces the incidence of wound infection after median sternotomy (from 16% to 3.9%) in this high-risk group of obese patients. Considering the reduction of SWI rate and the additional therapy costs caused by SWI, negative pressure wound therapy is also cost-effective in this high-risk group of patients.