SLR - October 2017 - Travis M. Johnson

Does Negative-Pressure Wound Therapy Influence Subjacent Bacterial Growth? A Systematic Review

Reference: Glass GE, Murphy GRF, Nanchahal J. Does Negative-Pressure Wound Therapy Influence Subjacent Bacterial Growth? A Systematic Review. J Plast Reconstr Aesthet Surg. 2017 Aug; 70(8), 1028–1037.

Scientific Literature Review

Reviewed By: Travis M. Johnson, DPM
Residency Program: The Western Pennsylvania Hospital, Pittsburgh, PA

Podiatric Relevance: Negative pressure wound therapy (NPWT) has become a mainstay of wound care in both the clinic and hospital settings since the publication of the seminal papers by Argenta and Morykwas in 1997 with widespread applications in open wound and more recently over sutured wounds of the lower extremities. The purported mechanisms of action, including bacterial clearance at the wound bed among others, have been widely accepted despite the publication of several studies that challenge that assumption. The true influence of NPWT on the microbiome of the subjacent wound remains unknown secondary to the many confounding variables that exist in studies that were designed to uncover it. The present systematic review sought to scrutinize all preexisting experimental and clinical data to definitively determine if negative pressure therapy works at least partially by decreasing the bacterial burden of the wound.

Methods: A search was performed in accordance with the Cochrane Highly Sensitive Search Strategy guideline of PubMed, Ovid Medline, the Cochrane database of systematic reviews and the Cochrane controlled trials register. Studies that met inclusion criteria were those that quantitatively measured the influence of NPWT on bacterial growth within the subjacent wound. Among those included were in vivo and in vitro studies, animal models, human clinical studies and randomized controlled trials. Excluded studies were those published prior to the modern description of NPWT (pre-1997), studies that reported qualitative data only and those that lacked a control. All papers considered for inclusion had their quality assessed using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) thereby drawing reasoned conclusions about each study’s quality of evidence.

Results: The main review was conducted on 24 papers that reported quantitative data on the effect of negative pressure wound therapy on the bacterial environment of the subjacent wound. Of the 24, there were 10 experimental studies, four randomized controlled trials and six clinical studies. Also included were four studies that evaluated NPWT with periodic installation. Seven studies concluded NPWT significantly reduced the wound bioburden at least one point in time relative to the control. However, eight of the included papers reached the conclusion that NPWT did not influence the bioburden independently. Five studies reported the selective suppression of nonfermentative gram-negative bacilli.

Conclusions: The assumption that NPWT works in part by reducing the bacterial bioburden of the subjacent wound is an oversimplification. The results of this systematic review call into question the findings of Morykwas et al, which have been used as justification for the use of NPWT on contaminated wounds under the expectation that it assists in cleaning the wound. Instead, the authors conclude that the effect is likely species dependent and that NPWT should be used in conjunction with surgical debridement. There is existing evidence that negative pressure therapy suppresses the proliferation of NFGNB, such as Pseudomonas aeruginosa. This effect may open that previously occupied niche for exploitation by gram-positive cocci. The authors state that the results of this systematic review warrant caution in the use of NPWT when highly virulent gram-positive cocci have been isolated. Additionally they advise caution with the length of NPWT therapy and the frequency of dressing changes. 

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