Summary of Evidence of Clinical Outcomes
Reference: Samson DJ, Lefevre F, Aronson N. Wound-Healing Technologies: Low-Level Laser and Vacuum-Assisted Closure. Evidence Report/Technology Assessment: Number 111. Rockville, Md: Agency for Healthcare Research and Quality; 2004. AHRQ Publication 05-E005-2.
Rationale: The Agency for Healthcare Research and Quality (AHRQ) sponsored a technology assessment of wound healing effects of low-level laser and negative pressure wound therapy (NPWT) through its Evidence-Based Practice Centers (EPCs) as requested by the American Association of Health Plans. Only NPWT evidence will be described here.
Objective: This systematic review summarized evidence of efficacy and safety of NPWT on wound healing in order to provide comprehensive, science-based information on which to base wound care decisions about these technologies.
Methods: The authors summarized English-language articles describing randomized, controlled, human clinical trials applying NPWT to chronic and acute wounds in settings across the continuum of care from hospitals to home care. They searched MEDLINE and EMBASE literature through June 2004 and the Cochrane Controlled Trials Register with most recent evidence from 2003. Primary efficacy outcomes were incidence of complete wound closure or time to complete closure. Adverse events measured safety. Secondary outcomes were facilitation of surgical closure, need for debridement, infections, pain, quality of life, improved cosmesis, and activities of daily living.
Results: Six controlled studies of NPWT with a collective total of 135 patients were identified. All were rated poor quality on the standardized study quality scale, generally due to lack of initial comparability of the treatment groups, poor randomization (except for the Moues study reported below), small numbers of patients, and inappropriate analyses. All studies used V.A.C.® Therapy™ (KCI, San Antonio, Tex) as the experimental treatment. Controls were typically moist dressings changed once daily. Incidence of complete healing was reported in only 1 study, in which 2 of 20 (10%) healed in the NPWT group and 2 of 15 (13%) patients healed when dressed with gel, pad, or enzyme products. There were no statistically significant healing time differences and mixed results for wound dimensions, wound volume reduction, and wound complications. KCI provided additional protocols, which, if successfully completed, may allow more definitive conclusions about the efficacy of NPWT.
Conclusions: The authors concluded that the currently available body of evidence was insufficient to support conclusions about the effectiveness of NPWT in the treatment of wounds.
Vacuum Effects on Wound Bacterial Burden and Closure
Reference: Moues CM, Vos MC, van den Bemd GJ, Stijnen T, Hovius SE. Bacterial load in relation to vacuum-assisted closure wound therapy: a prospective randomized trial. Wound Repair Regen. 2004;12(1):11–17.
Rationale: Negative pressure wound therapy has been used increasingly in the management of contaminated acute and chronic wounds with little scientific proof of its mechanism of action in wound care.
Objective: The objective of the study was to compare healing outcomes and bacterial burden of open wounds being prepared for surgical closure managed with either NPWT or saline gauze.
Methods: Patients with open full-thickness wounds that could not be surgically closed immediately due to chronic status, infection, or contamination were randomly assigned to up to 30 days’ management with NPWT or moist gauze. Negative pressure wound therapy (n=29) administered 125mmHg of continuous negative pressure therapy through a polyurethane foam dressing with pore size of 400–600mm changed every 48 hours. Gauze (n=25) moistened with 0.9% sodium chloride solution plus optional 0.2% nitrofuralin, 1% acetic acid, or 2% sodium hypochlorite was changed at least twice daily as needed to manage exudate. All wounds were debrided as clinically necessary. The healing outcome was assessed every 48 hours and analyzed using Kaplan-Meier “survival” time until the wound was rated “ready for surgical therapy” defined as having a clean, red, granulated wound bed. Wound surface area was measured by tracing immediately after debridement on enrollment and at least once during treatment. Biopsies free of wound surface exudate were harvested from each wound center at varying periods during treatment and cultured under aerobic and anaerobic conditions.
Results: There were no statistically significant differences between the NPWT and moist gauze groups in median time to reach wound status “ready for surgical therapy” in bacterial load reduction of aerobic or anaerobic microorganisms or in percent of wounds with <105 colony-forming units wound biopsy bioburden at the study end. Wound surface area reduction was significantly greater in the 13 NPWT-treated wounds than in the 15 gauze-treated wounds for which this measure was reported (p<0.05), but these results were not related to the biopsy bioburdens.
Conclusions: Negative pressure wound therapy positively affected wound area reduction but not time to reach “ready for surgical therapy” status as compared to moist gauze. The effect on wound area reduction was not associated with a significant quantitative reduction in wound bacterial load.
The limited evidence currently available appears insufficient to support clinical efficacy of NPWT in increasing the probability of complete healing or reducing time to healing or preparation for surgical closure. With a few exceptions, the literature lacked rigorous reporting of these accepted healing outcomes. From a clinical perspective, the typical control dressing in this evidence, gauze, is of doubtful virtue in wound care.1–3 No evidence was available comparing wound healing, wound-related pain, safety, or health economic efficacy of NPWT with wound care products more advanced than gauze, such as alginate or other fibrous or composite dressing designed to manage heavily exuding wounds. In terms of meeting wounds’ clinical needs, NPWT appears to serve a measurable function of managing large volumes of wound exudate, but its clinical safety and efficacy for healing remain to be established, particularly relative to modern wound care.
1. van Rijswijk L. Moist dressings: bridging the gap between research and practice. Adv Skin Wound Care. 2004;17(5):254–255.
2. Kerstein MD, Gemmen E, van Rijswijk L, et al. Cost and cost effectiveness of venous and pressure ulcer protocols of care. Disease Management and Health Outcomes. 2001;9(11):651–636.
3. Bolton L, McNees P, van Rijswijk L, et al. Wound healing outcomes using standardized care. J Wound Ostomy Continence Nurs. 2004;31(3):65–71.
* V.A.C. and Vacuum Assisted Closure are registered trademarks of KCI Licensing, Inc., an affiliate of KCI, USA, Inc., San Antonio, Tex