Surgical wounds healing by secondary intention : characterising and quantifying the problem, identifying effective treatments, and assessing the feasibility of conducting a randomised controlled trial of negative pressure wound therapy versus usual care

Abstract Background: Most surgical incisions heal by primary intention (i.e. wound edges are apposed with sutures, clips or glue); however some heal by secondary intention (i.e. the wound is left open and heals by formation of granulation tissue). There is, however, a lack of evidence regarding the epidemiology, management, and impact on patients’ quality of life of these surgical wounds healing by secondary intention (SWHSI), resulting in uncertainty regarding effective treatments and difficulty in planning care and research. Objectives: To derive a better understanding of the nature, extent, costs, impact and outcomes of SWHSI, effective treatments and the value and nature of further research. Design: Cross-sectional survey; inception cohort; cost-effectiveness and value of implementation analyses; qualitative interviews; and a pilot, feasibility randomised controlled trial (RCT). Setting: Acute and community care settings in Leeds and Hull, Yorkshire, UK. Participants: Adults with (or for qualitative interviews, patients or practitioners with previous experience of) a SWHSI. Inclusion criteria varied between the individual Workstreams. Interventions: The pilot, feasibility RCT compared negative pressure wound therapy (NPWT) – a device applying a controlled vacuum to a wound via a dressing - with Usual Care (no NPWT). Results: Survey data estimated that treated SWHSI have a point prevalence of 4.1 per 10,000 population (95% CI: 3.5 to 4.7). SWHSI most frequently occurred following colorectal surgery (n=80, 42.8% - Cross-sectional survey, n=136, 39.7% - Inception cohort), and were often planned before surgery (n=89, 47.6% - Survey, n=236, 60.1% - Cohort). Wound care was frequently delivered in community settings (n=109, 58.3%) and most patients (n=184, 98.4%) received active wound treatment. Cohort data identified hydrofibre dressings (n=259, 65.9%) as the most common treatment, although 29.3% (n=115) participants used NPWT at some time during the study. SWHSI healing occurred in 81.4% (n=320) of participants at a median of 86 days (95% CI: 75 to 103). Baseline wound area (p=<0.01), surgical wound contamination (determined during surgery) (p=0.04) and wound infection at any time (p=<0.01) (i.e. at baseline or post-operatively) were found to be predictors of prolonged healing. Econometric models, using observational, cohort study data, identified that with little uncertainty, that NPWT treatment is more costly and less effective than standard dressing treatment for the healing of open surgical wounds: Model A (ordinary least squares with imputation): Effectiveness: 73 days longer than those who did not receive NPWT (95% Credible Interval (CrI): 33.8 to 112.8); Cost Effectiveness (Associated incremental quality adjusted life years): -0.012 (SE 0.005) (Observables); -0.008 (SE 0.011) (Unobservables) , Model B (Two Stage Model – Logistic and linear regression): Effectiveness: 46 days longer the those who did not receive NPWT (95% CrI: 19.6 to 72.5); Cost Effectiveness (Associated incremental quality adjusted life years): -0.007 (Observables) and -0.027 (Unobservables) (SE 0.017). Patient interviews (n=20) identified initial reactions to SWHSI of shock and disbelief. Impaired quality of life characterised the long healing process, with particular impact on daily living for patients with families or in paid employment. Patients were willing to try any treatment promising wound healing. Health professionals (n=12) had variable knowledge of SWHSI treatments, and frequently favoured NPWT despite the lack of robust evidence, The pilot, feasibility RCT screened 248 patients for eligibility and subsequently recruited and randomised 40 participants to receive NPWT or Usual Care (no NPWT). Data indicated that it was feasible to complete a full RCT to provide definitive evidence for the effectiveness of NPWT as a treatment for SWHSI. Key elements and recommendations for a larger RCT were identified. Limitations: This research programme was conducted in a single geographical area (Yorkshire and the Humber, UK) and local guidelines and practices may have affected treatment availability and so may not represent UK wide treatment choices. A wide range of wound types were included, however, some wound types may be underrepresented meaning this research may not represent the overall SWHSI population. The lack of RCT data on the relative effects of NPWT in SWHSI resulted in much of the economic modelling being based on observational data. Observational data, even with adjustment, does not negate the potential for unresolved confounding to affect the results. This may reduce confidence in the conclusions drawn and may lead to calls for definitive evidence from an RCT. Conclusions: This research has provided new information regarding the nature, extent, costs, impacts and outcomes of SWHSI, treatment effectiveness and the value and nature of future research; addressing previous uncertainties regarding the problem of SWHSI. Aspects of our research indicate that NPWT is more costly and less effective than standard dressing for the healing of open surgical wounds. However, because this conclusion is based solely on observational data it may be affected by unresolved confounding. Should a future RCT be considered necessary, its design should reflect careful consideration of the findings of this programme of research. Trial registration: Pilot, feasibility RCT registration: ISRCTN12761776. Funding: This project was funded by the NIHR Programme Grants for Applied Research (RP-PG-0609-10171).