Negative pressure wound therapy for surgical wounds healing by primary closure

BACKGROUND: Indications for the use of negative pressure wound therapy (NPWT) are broad and include prophylaxis for surgical site infections (SSIs). Existing evidence for the effectiveness of NPWT on postoperative wounds healing by primary closure remains uncertain. OBJECTIVES: To assess the effects of NPWT for preventing SSI in wounds healing through primary closure, and to assess the cost‐effectiveness of NPWT in wounds healing through primary closure. SEARCH METHODS: In January 2021, we searched the Cochrane Wounds Specialised Register; the Cochrane Central Register of Controlled Trials (CENTRAL); Ovid MEDLINE (including In‐Process & Other Non‐Indexed Citations); Ovid Embase and EBSCO CINAHL Plus. We also searched clinical trials registries and references of included studies, systematic reviews and health technology reports. There were no restrictions on language, publication date or study setting. SELECTION CRITERIA: We included trials if they allocated participants to treatment randomly and compared NPWT with any other type of wound dressing, or compared one type of NPWT with another. DATA COLLECTION AND ANALYSIS: At least two review authors independently assessed trials using predetermined inclusion criteria. We carried out data extraction, assessment using the Cochrane risk of bias tool, and quality assessment according to Grading of Recommendations, Assessment, Development and Evaluations methodology. Our primary outcomes were SSI, mortality, and wound dehiscence. MAIN RESULTS: In this fourth update, we added 18 new randomised controlled trials (RCTs) and one new economic study, resulting in a total of 62 RCTs (13,340 included participants) and six economic studies. Studies evaluated NPWT in a wide range of surgeries, including orthopaedic, obstetric, vascular and general procedures. All studies compared NPWT with standard dressings. Most studies had unclear or high risk of bias for at least one key domain. Primary outcomes Eleven studies (6384 participants) which reported mortality were pooled. There is low‐certainty evidence showing there may be a reduced risk of death after surgery for people treated with NPWT (0.84%) compared with standard dressings (1.17%) but there is uncertainty around this as confidence intervals include risk of benefits and harm; risk ratio (RR) 0.78 (95% CI 0.47 to 1.30; I(2) = 0%). Fifty‐four studies reported SSI; 44 studies (11,403 participants) were pooled. There is moderate‐certainty evidence that NPWT probably results in fewer SSIs (8.7% of participants) than treatment with standard dressings (11.75%) after surgery; RR 0.73 (95% CI 0.63 to 0.85; I(2) = 29%). Thirty studies reported wound dehiscence; 23 studies (8724 participants) were pooled. There is moderate‐certainty evidence that there is probably little or no difference in dehiscence between people treated with NPWT (6.62%) and those treated with standard dressing (6.97%), although there is imprecision around the estimate that includes risk of benefit and harms; RR 0.97 (95% CI 0.82 to 1.16; I(2) = 4%). Evidence was downgraded for imprecision, risk of bias, or a combination of these. Secondary outcomes There is low‐certainty evidence for the outcomes of reoperation and seroma; in each case, confidence intervals included both benefit and harm. There may be a reduced risk of reoperation favouring the standard dressing arm, but this was imprecise: RR 1.13 (95% CI 0.91 to 1.41; I(2) = 2%; 18 trials; 6272 participants). There may be a reduced risk of seroma for people treated with NPWT but this is imprecise: the RR was 0.82 (95% CI 0.65 to 1.05; I(2) = 0%; 15 trials; 5436 participants). For skin blisters, there is low‐certainty evidence that people treated with NPWT may be more likely to develop skin blisters compared with those treated with standard dressing (RR 3.55; 95% CI 1.43 to 8.77; I(2) = 74%; 11 trials; 5015 participants). The effect of NPWT on haematoma is uncertain (RR 0.79; 95 % CI 0.48 to 1.30; I(2) = 0%; 17 trials; 5909 participants; very low‐certainty evidence). There is low‐certainty evidence of little to no difference in reported pain between groups. Pain was measured in different ways and most studies could not be pooled; this GRADE assessment is based on all fourteen trials reporting pain; the pooled RR for the proportion of participants who experienced pain was 1.52 (95% CI 0.20, 11.31; I(2) = 34%; two studies; 632 participants). Cost‐effectiveness Six economic studies, based wholly or partially on trials in our review, assessed the cost‐effectiveness of NPWT compared with standard care. They considered NPWT in five indications: caesarean sections in obese women; surgery for lower limb fracture; knee/hip arthroplasty; coronary artery bypass grafts; and vascular surgery with inguinal incisions. They calculated quality‐adjusted life‐years or an equivalent, and produced estimates of the treatments' relative cost‐effectiveness. The reporting quality was good but the evidence certainty varied from moderate to very low. There is moderate‐certainty evidence that NPWT in surgery for lower limb fracture was not cost‐effective at any threshold of willingness‐to‐pay and that NPWT is probably cost‐effective in obese women undergoing caesarean section. Other studies found low or very low‐certainty evidence indicating that NPWT may be cost‐effective for the indications assessed. AUTHORS' CONCLUSIONS: People with primary closure of their surgical wound and treated prophylactically with NPWT following surgery probably experience fewer SSIs than people treated with standard dressings but there is probably no difference in wound dehiscence (moderate‐certainty evidence). There may be a reduced risk of death after surgery for people treated with NPWT compared with standard dressings but there is uncertainty around this as confidence intervals include risk of benefit and harm (low‐certainty evidence). People treated with NPWT may experience more instances of skin blistering compared with standard dressing treatment (low‐certainty evidence). There are no clear differences in other secondary outcomes where most evidence is low or very low‐certainty. Assessments of cost‐effectiveness of NPWT produced differing results in different indications. There is a large number of ongoing studies, the results of which may change the findings of this review. Decisions about use of NPWT should take into account surgical indication and setting and consider evidence for all outcomes.