Cost-effectiveness analysis of single use negative pressure wound therapy dressings (sNPWT) compared to standard of care in reducing surgical site complications (SSC) in patients undergoing coronary artery bypass grafting surgery

There has been advances in infection control practices and wound dressings yet surgical site infections (SSI) remains common in patients undergoing surgery [1‐4]. European Centre for Disease Prevention and Control (ECDC) reports that SSI are among the most common healthcare-associated infections (HAIs) which occur after surgery in the area of the body where the surgery took place. European-wide SSI incidence rates range from 0.7% in knee prosthesis to 9.7% in colon surgery [2]. Reddy et al. [3], reported that approximately 0.3–5% of median sternotomy incisions are affected by complications, such as infection and dehiscence.

Surgical site infections impacts on morbidity, health- related quality of life, longer post-operative hospital stays, additional surgical procedures, mortality and increased costs [4‐10]. Graf et al. [6] estimated the financial loss to a hospital due to deep sternal wound infection following coronary artery by-pass surgery to be $12,482 (€9154) in Germany. In the United Kingdom, attributable median hospital length of stay (LOS) due to SSI for cardiac patients is estimated to be 23 days and the attributable median costs due to SSI are £11,003 ($8517- $15,395) respectively [10].

Many strategies have been introduced to control SSI, ranging from antibiotics prophylaxis, dressings and new protocols including the use of single use negative pressure wound therapy (sNPWT). Evidence on the clinical effectiveness of sNPWT is accumulating rapidly [11, 14, 15] and has been shown to be effective in reducing SSI in closed incisions such as in caesarean-section, orthopaedic and cardiac surgery. Cost-effectiveness studies have been performed in patients undergoing caesarean-section [13] and Orthopaedic surgery [12], however the cost-effectiveness of sNPWT following cardiothoracic surgery has not been reported.

This study therefore examined the cost-effectiveness of sNPWT PICO^◊ (Smith & Nephew, Hull, UK) compared with standard care dressing (standard post-operative dressings) in preventing surgical site complications defined as dehiscence and sternotomy infections in patients undergoing coronary artery by-pass (CABG) surgery from a Germany Insurance payer’s perspective.

To describe the clinical problem, we constructed a decision analytic model in Microsoft Excel 2016 (Microsoft Corporation, Redmond, WA, US) to simulate the expected outcomes and costs of patients undergoing CABG surgery. The mean age of patients that were modelled is 65 years, which represents the mean age of the majority of patients included in the studies were baseline and effectiveness data were drawn from [16, 17]. Following skin closure, one group would be managed by sNPWT while the other group would receive standard of care dressings. The modeled patients may develop complications of sternotomy wounds which in this model was defined as SSI (superficial and deep wound infections) or dehiscence. The complications are assumed to result in readmissions and revision surgery in some cases as shown in Fig. 1. The model assumed a proportion of patients could die from natural causes and also die due to surgery. The perspective adopted was that of the Statutory Health Insurance payers in Germany. The economic model adopted a 12 week time horizon to enable the both superficial and deep infection to manifest themselves. Superficial SSI usually occurs within 30 days after surgery while deep SSI normally occurs within 30 to 90 days following surgery [1]. No discounting was done for both costs and outcomes due to a shorter time horizon (12 weeks). The schematic representation of the model is shown below in Fig. 1, showing the branches of the complications node, there are similar branches for the no complications node not shown in the figure.

The total mean costs per patient in the sNPWT group were lower than the total mean costs per patient in the standard care group. The use of sNPWT was associated with more QALYs and fewer wound related complications compared to the use of standard care. Overall, the use of sNPWT is a dominant strategy (cost-saving) compared to standard care as it costs less and results in better clinical outcomes as shown in Table 3.

This study examined the cost-effectiveness analysis of sNPWT compared to standard of care dressings in preventing SSI for patients undergoing CABG. The results of the study suggest that treating patients undergoing CABG with sNPWT is cost-saving resulting better clinical outcomes (0.311 more QALYs) and cheaper overall, with cost savings of €586 per patient. The probability of sNPWT being cost-effective is 100%, indicating decision certainty and little chance of error in a decision based on this cost-effectiveness analysis.

A limited number of cost-effectiveness studies evaluating the use of sNPWT in closed incisions have been published [12, 13] and they conclude that negative pressure wound therapy is cost-effective. However, to our knowledge, there is no published data on cost-effectiveness analysis of sNPWT in preventing wound complications following CABG surgery. This may be explained by lack of clinical evidence to support sNPWT as we found out during the literature search. As noted earlier, we are aware of an ongoing clinical trial comparing sNPWT with standard care following CABG surgery (Dr Carlos Velasco; Hospital Juan Canalejo, Spain; personal communication).

The model adopted a number of conservative assumptions so the projected savings may actually under-estimate the true financial impact. For instance, we only captured SSI as an outcome and did not include other outcomes such as healing. Potentially infected wounds will take longer to heal and might develop into chronic wounds which are costly to treat [24]. Equally, dressing changes was not captured as an outcome, however we know based on previous studies that infected wounds would require more dressing changes making the model conservative favoring the strategy with more SSIs. For instance there were few dressing changes in the sNPWT group (p = 0.002) compared to standard care after hip and knee surgery, while there were more wounds with superficial infections in the standard care arm [11].

Given the diversity of health systems across the world, the results of this analysis should be interpreted with caution. We acknowledge that the reimbursement systems, relative prices, and treatment practices, are important issues that vary from country to country hence country-specific assumptions may be required. However, we note that our cost-effectiveness results were tested in sensitivity analysis and the RCT measured SSI in a standard way using the ECDC matrix. A study by Hansen 2012, found that there was a high degree of concordance between European and US case definitions of healthcare-associated infections [25]. Therefore, the measurement of SSI in a standard way suggests that the results of the RCT which drive the cost-effectiveness are likely to be replicated in setting with similar baseline risks. Furthermore, our model is based on clinical data that comes from a single center RCT, multi center trials should be preferred as they yield data which is easily generalisable. We therefore encourage other scholars to update the economic model once additional evidence becomes available.

Our analysis found sNPWT to be less costly and more effective (dominant), resulting in an overall cost decrease of €586 per patient when used prophylactically in patients undergoing coronary artery by-pass surgery. These results remained stable in sensitivity analyses with bigger savings identified in sub-groups of patients with elevated risk of surgical site complications such as those patients with diabetes, obese and smokers. We however recommend that additional economic studies should be conducted as new evidence on the use of sNPWT in CABG patients becomes available to validate the results of this economic analysis.