Cath Lab Digest

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Index: Ostomy Wound Management 2011;57(12):30–35

Abstract

  Pain upon negative pressure wound therapy (NPWT) dressing removal has been reported and is believed to be associated with the observation that granulation tissue grows into foam. Wound tissue damage upon removal of the foam may cause the reported pain. Calcitonin gene-related peptide (CGRP) and substance P are neuropeptides that cause inflammation and signal pain and are known to be released when tissue trauma occurs. The aim of this controlled in vivo study was to compare the expression of CGRP and substance P in the wound bed in control wounds and following NPWT and foam or gauze dressing removal. Eight pigs with two wounds each were treated with open-pore structure polyurethane foam or AMD gauze and NPWT of 0 (control) or -80 mm Hg for 72 hours. Following removal of the wound filler, the expression of CGRP and substance P was measured, using arbitrary units, in sections of biopsies from the wound bed using immunofluorescence techniques. Substance P and CGRP were more abundant in the wound edge following the removal of foam than of gauze dressings and least abundant in control wounds. The immunofluorescence staining of the wound edge for CGRP was 52 ± 3 au after the removal of gauze and 97 ± 5 au after the removal of foam (P <0.001). For substance P, the staining was 55 ± 3 au after gauze removal and 95 ± 4 au after foam removal (P <0.001). CGRP and substance P staining was primarily located to nerves and leukocytes. The increase in CGRP and substance P immunofluorescence was especially prominent in the dermis but also was seen in subcutaneous and muscle tissue. Using gauze may be one way of reducing NPWT dressing change-related pain. New wound fillers designed to optimize granulation tissue formation and minimize pain issues presumably will be developed in the near future.

Keywords: animal model, controlled study, negative pressure wound therapy, pain, dressing

Potential Conflicts of Interest: This study was supported by the Swedish Medical Research Council, Lund University Faculty of Medicine, the Swedish Government Grant for Clinical Research, Lund University Hospital Research Grants, the Swedish Medical Association, the Royal Physiographic Society in Lund, the Ake Wiberg Foundation, the Anders Otto Swärd Foundation/Ulrika Eklund Foundation, the Magn Bergvall Foundation, the Crafoord Foundation, the Anna-Lisa and Sven-Erik Nilsson Foundation, the Jeanssom Foundation, the Swedish Heart-Lung Foundation, Anna and Edvin Berger’s Foundation, the Märta Lundqvist Foundation, Lars Hierta’s Memorial Foundation, and Prospera (Forth Worth, TX).

  The most commonly used wound filler materials for negative pressure wound therapy (NPWT) are open-pore polyurethane foam or cotton gauze (eg, Kerlix, AMD gauze, Covidien, Mansfield, MA) dressings.¹ The results of in vivo studies have shown that dressing choice can affect the healing process, because both the amount and characteristics of granulation tissue are different when foam or gauze dressings are used.^2-4 In a preclinical experimental wound models in dogs and pigs, newly formed granulation tissue was found to be thick but fragile; when gauze was used, the newly formed tissue was thinner and more stable.^2,5 Thick granulation tissue is beneficial for rapid wound healing, but results from a clinical study of patients indicate this may lead to problems such as fibrosis, scarring, and contractures as the wound heals.⁴

  Gauze often is used for NPWT because of its moldability and ease of application, advantages described by Jeffery et al⁶ in a review of treatment modalities for wounds in military personnel caused by landmines and other explosive devices.