Controversy Surrounding Wound-edge Protectors

Surgical site infections (SSIs) occur in 5% of all surgeries and up to 40% of laparotomies,^1,2 significantly increasing patient morbidity and mortality as well as health care costs.³ Despite development of techniques to reduce the incidence of SSIs such as preoperative antibiotic prophylaxis,⁴ clipping hair if needed to clear the operative site,⁵ and antiseptic skin preparation,⁶ SSIs remain one of the most frequent complications following abdominal surgery. One practice believed to reduce the likelihood of a SSI is the use of circular single-ring or dual-ring wound-edge protective devices (WEPs) designed to provide a physical barrier protecting the wound edge from visceral contamination. Single-ring WEPs have a semirigid ring that is placed into the open abdomen, with an impervious drape extending out of the abdomen over the surrounding skin. Dual-ring WEPs add a second ring attached to the external edge of the impervious drape. Controversy emerged about the efficacy of WEPs until recent meta-analyses^7,8 confirmed their efficacy in reducing SSI incidence. This Evidence Corner explores the resolution of this controversy, describing 1 large study concluding that WEPs were an ineffective waste of health care resources³ and 1 of a meta-analysis⁸ supporting WEP efficacy in preventing SSIs.

Reference: Gheorghe A, Roberts TE, Pinkney TD, Bartlett DC, Morton D, Calvert M;  West Midlands Research Collaborative; ROSSINI Trial Investigators. The cost-effectiveness of wound-edge protection devices compared to standard care in reducing surgical site infection after laparotomy: an economic evaluation alongside the ROSSINI trial. PLoS One. 2014;9(4):e95595. doi: 10.1371/journal.pone.0095595.

Rationale: Though wound-edge protectors (WEPs) had been used for more than 40 years, at the time of the ROSSINI (Reduction of Surgical Site Infection using a Novel Intervention) trial, only weak randomized, controlled trials (RCTs) supported their efficacy in abdominal surgery and no RCTs supported their cost effectiveness.

Objective: Analyze data from the large, high quality ROSSINI RCT to determine efficacy and cost effectiveness of WEPs in reducing SSI incidence.

Methods: Using cost-effectiveness analysis principles set forth by the Consolidated Health Economic Evaluation Reporting Standards (CHEERS) Statement,⁹ relevant costs of the WEP intervention plus the costs of subsequent hospital, intensive care unit, primary care, nursing visits, outpatient clinic visits, and medication were summed for all patients participating in the United Kingdom-based prospective, multicenter, observe-blinded ROSSINI trial comparing WEP use to standard of care. Patients were randomized to either receive a WEP (n = 369) or standard of care (n = 366) during the laparotomy, after which SSI surveillance followed for 30 days. Surgical teams used retraction and SSI prophylactic procedures as their choices to increase generalizability of results. Resource utilization data were collected on customized case report forms. Associated unit costs were in 2011 British pounds, based on British National Health Service sources and manufacturers costs for the WEP products used. Cost effectiveness was calculated as the utility weight of cost and resource used to derive each quality-adjusted life year (QALY). Quality-adjusted life years were calculated by multiplying the utility weight associated with each health state by the time spent in the health state, derived from patient responses to the EURO-QoL EQ-5D questionnaire administered before surgery, then 5-7 days and 30-33 days postoperatively. Mean differences between the 2 groups’ costs and outcomes were calculated after iteratively adjusting for potential bias factors. Incremental costs and effects were plotted for the WEP group relative to the non-WEP group. Cost effectiveness acceptability curves were displayed as the likelihood that each alternative treatment would be acceptable, based on user’s willingness to pay for each added unit of clinical outcome.

Results: Surgical site infections were reported in 91 (24.7%) of WEP patients and 93 (25.4%) of controls. The relationship between incremental QALYs and incremental costs was uncertain as estimates of both varied widely. More than 20% of patients had missing resource use or EQ-5D outcome data, mainly at the 30-33 day evaluation (14%). Incremental QALYs were similar for WEP (0.02131) and control subjects (0.02133), while the incremental cost of using WEP was ₤209. The cost-effectiveness acceptability curve results showed WEP 30% likely to be cost effective according to National Institute for Health and Clinical Excellence criteria. These results reporting significant cost for minimal QALY improvement were robust for all sensitivity analyses.

Authors’ Conclusions: Wound-edge protectors “are unlikely to be cost-effective compared to standard care and their use cannot be recommended.

Reference: Zhang MX, Sun YH, Xu Z, Zhou P, Wang HX, Wu YY. Wound edge protector for prevention of surgical site infection in laparotomy: an updated systematic review and meta-analysis [published online ahead of print Feb 3, 2015]. ANZ J Surg. 2015;85(5):308-314.

Rationale: Preventing SSIs is more cost effective than treating them. Wound-edge protectors have been reported effective in preventing SSI in some abdominal surgery studies, but not others, causing controversy about WEP efficacy in reducing SSI incidence.

Objective: Update a systematic review of WEP effects on SSI following laparotomy.

Methods: Authors searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, and secondary references for English-language RCT evidence testing effects on SSI incidence resulting from use or non-use of a WEP during a laparotomy. Titles and abstracts were evaluated for inclusion by 2 independent reviewers who were blinded to source authors and institutions and who resolved disagreements by discussion. Evidence quality was based on standardized criteria including randomization, baseline comparability of groups, and potential bias. Meta-analysis of the main outcome, SSI incidence, was performed using the Review Manager (RevMan) 5.2 (The Nordic Cochrane Centre, The Cochrane Collaboration, Copenhagen, Denmark) applying a random effects model with relative risk of a pooled effect on SSI expressed as a 95% confidence interval. A 2-tailed Z-test estimated significance of the difference between WEP and control treatment effects, with I² tests of data heterogeneity and funnel plot estimates of potential publication bias. Subset analyses explored effects of single-ring vs dual-ring WEPs and baseline levels of wound contamination.

Results: Eleven RCTs on 2344 patients undergoing laparotomy between 1977 and 2013 in Asia, Europe, or the United States were included in the analysis. Most subjects were undergoing gastrointestinal surgery, except for 1 study each on Cesarean section or appendectomy. Definitions of SSI differed across studies and were defined using either the Centers for Disease Control and Prevention or the study authors’ criteria. Most studies were at high risk of clinical or methodological bias, with significant (P = 0.002) heterogeneity. Single-ring WEPs used in 6 RCTs (1589 subjects) did not show a significant reduction of SSI following laparotomy (P = 0.17). Asymmetry of the funnel plot suggested existence of unpublished small studies with negative results. After introduction of dual-ring WEPs in 2005, five RCTs on 755 laparotomy patients randomized to receive either dual-ring WEP or standard of care did report significantly reduced SSI incidence with a dual-ring WEP (P < 0.0002). Combined meta-analysis of all 11 WEP RCTs also reduced SSI incidence (P = 0.0008). Subset analyses showed that a WEP significantly reduced SSI incidence on contaminated incisions (RR 0.43, 95% CI 0.26–0.72), but not on clean/contaminated or dirty incisions. This effect remained significant even when antibiotic prophylaxis was used as standard of care.

Authors’ Conclusions: Wound-edge protectors reduce the incidence of laparotomy SSI compared to standard of care in contaminated incisions.

Zhang and colleagues⁸ clarify the controversy surrounding WEP efficacy, presenting compelling evidence that WEP use reduces the likelihood of SSI in contaminated laparotomy incisions. Their study points out that effects are less likely to be seen on clean/contaminated incisions, which are already at low SSI risk, or on dirty incisions, soiled before WEP application. Zhang and coauthors also note that the more consistent capacity of dual-ring WEPs to reduce SSI compared to single-ring WEPs may result from improvements in SSI prevention protocols between the year 2000, when the last single-ring WEP study began, and when dual-ring WEPs were introduced in 2005. Their findings were confirmed by a meta-analysis by Mihaljevic et al⁷ which included 16 RCTs (3695 patients) conducted from 1972 to 2014, concluding that WEPs significantly reduce SSI likelihood by 32% to 35%. Their broader meta-analysis⁷ calculated that 15 patients would need to be treated with a WEP to prevent 1 SSI. 

One can learn from the ROSSINI RCT cost-effectiveness analysis³ how study protocols and assumptions can obscure clinically important findings like those reported in the 2 meta-analyses.^7,8 The authors’ intent to enhance generalizability by allowing staff to choose methods of SSI prevention³ may have increased SSI variability and likelihood. Consistent practice of an SSI prevention bundle reduces both incidence and costs of SSI in colorectal surgery.¹⁰ Gheorghe et al³ note another limitation of their study in failing to include dressing costs in their economic analysis, assuming it was adequately covered within nursing visits. They neglected to address the fact that wound dressings affect likelihood of infection. Traditional gauze dressing use is associated with 3 to 5 times the incidence of acute surgical^11,12 or all wound infections¹³ compared to moisture-retentive hydrocolloid or film dressings. Using this simple fact can enhance SSI outcomes or incidence of all wound infections. Not consistently using SSI prevention bundles or moisture-retentive dressings places any study of SSI at risk of wide variability and elevated infection rates. If SSIs are to be used as performance indicators¹⁴ for institutions or clinical practice, it may be well to heed this important evidence as well as WEP efficacy in reducing contaminated laparotomy SSI.

Laura Bolton, PhD
Department of Surgery,
Rutgers Robert Wood Johnson Medical School, 
New Brunswick, NJ

Disclosure: This article was not subject to the WOUNDS peer-review process.