THE USE OF A PROTEASE INHIBITOR DRESSING IN COMBINATION WITH NEGATIVE PRESSURE WOUND THERAPY
INTRODUCTION Surgical Site Infections (SSI) continue to be a devastating complication in cardiac surgery. There are known risk factors such as obesity, diabetes and immunosuppression that can influence the development of sternal wound infection which, ultimately, can lead to complete wound dehiscence. Negative Pressure Wound Therapy (NPWT) is widely used as a treatment for sternal dehiscence as it promotes healing by the drainage of excessive fluid and debris by mechanical deformation of the wound1. However, in our experience, some wounds become static despite NPWT and require further assessment regarding barriers to wound healing. Elevated protease levels can be one such barrier. METHOD AND RESULTS This case study discusses the post-operative management of a 57 year old gentleman who was referred to the tissue viability service with an infected, dehisced sternal wound following an orthotopic heart transplant. His condition was further complicated by the diagnosis of pyoderma gangrenosum to the peri- wound skin. Day 33 Debridement of wound and subcutaneous Post op necrotic tissue and negative pressure wound therapy (NPWT) was applied in theatre. Day 36 Wound 30% slough and 70% granulation tissue. Day 39 Multiple lesions were noted under and surrounding the drape. Referral to dermatology and biopsy taken of peri-wound skin. Wound sloughy and visible wires. Day 40 Wound review: sloughy with pale green exudate: pericardial effusion fluid. Returned to theatre for exploration and re- application of NPWT. Calcium alginate Sorbsan Plus commenced under drape.
Day 41 Confirmation Pyoderma Gangrenosum to chest lesions. Day 44 Sternal wound debridement, wires tightened and reapplication of NPWT in theatre. Day 57 Wound measured: 19.7cm x 5.5cm x 2.5cm 10% slough 90% granulation tissue. Sternal wires visible. On wound assessment it was clear that the wound was not progressing along an expected trajectory. Given minimal changes following antibiotic treatment elevated proteases were considered as a possible barrier to wound healing. It was decided to line the wound bed with UrgoStart Contact to inhibit the protease activity. Pyoderma Gangrenosum lesions improving, drier and bruising decreasing. UrgoStart Contact commenced as wound liner. Day 61 Wound Measured: 19cm x 5.5cm x 2.2cm 10% slough, 90% granulation tissue. Day 64 Wound Measured: 20cm x 4cm x 1cm 10% slough, 90% red granulation tissue. More granulation noted over sternal wires. Day 69 Wound Measured 20cm x 5.2cm x 1.5cm 20% slough, 80% granulation tissue. Less sternal wires visible. Lesions dried and healed to most areas. UrgoStart Contact + NPWT renewed. Day 71 Wound Measured 19cm x 4.9cm x 0.9cm 89% red granulation tissue, 1% visible wire, 10% slough. Day 76 Wound Measured 19cm x 4.9cm x 0.9cm 10% slough, 90% granulation tissue. No wires visible. UrgoStart Contact + NPWT renewed. Day 81 UrgoStart Contact + NPWT renewed Prepared for discharge and continuation of dressing renewals by District Nurses Day 105 Wound Measured 17cm x 4cm Post op 5% slough, 5% adipose, 90% granulation UrgoStart Contact.
DISCUSSION It is acknowledged that if wounds do not progress as expected along the appropriate healing trajectory, given the correct treatment, there is a risk of the wound becoming static. With such surgery and frequent return visits to theatre the specialist clinician, on recognising the reduced progression of wound healing, must amend the planned wound care immediately. Matrix metalloproteinases (MMPs) are enzymes a type of protease that are essential for breaking down proteins in order for new tissues to form during normal wound healing2. However, when levels of MMPs are too high, present for lengthy periods and are in the wrong places they can destroy proteins required for healing to take place2. In this case study whilst antibiotics had dealt with infection there was little progress in wound healing leading the tissue viability nurse specialists to suspect an imbalance of MMPs within the wound. The protease inhibitory dressing, UrgoStart® Contact, is a contact layer with TLC-NOSF Technology (polyester mesh impregnated with hydrocolloid, petroleum jelly and protease inhibitor NOSF particles3,4) and the rationale for Tissue Viability’s choice for use was: • Promotes faster healing and improves patients’ quality of life • Neutralises excess proteases (MMPs) • Re-establishes wound equilibrium • Additional benefits of: pain-free dressing changes, moist wound-healing environment, history of good tolerance and proven stimulation of fibroblast proliferation • Additionally it has been clinically proven in a Double-blind Randomised Controlled Trial Furthermore, an extra reasoning for use was previous success under NPWT. Within this trust it is not routinely used as first line with NPWT but if wound progression is not as expected UrgoStart Contact is chosen. CONCLUSION Although this is a single patient case study it does begin to highlight the possibilities for using UrgoStart Contact under NPWT. It allows inhibition of MMPs whilst harnessing the known benefits of NPWT for both wound healing and mechanical wound support, particularly in the sternal region. This gentleman’s wound went on to heal completely within weeks of discharge