Thursday, June 23, 2011

Does Negative Pressure Promote Wound Healing? -- article review

Updated 3/2017-- all links (except to my own posts) removed as many no longer active. 

There was a recent EurekAlert which caught my attention:  No healing in a vacuum. 
Negative-pressure wound therapy probably does not promote healing. This is the conclusion of Frank Peinemann and Stefan Sauerland's meta-analysis in the current edition of Deutsches Ärzteblatt International (Dtsch Arztebl Int 2011; 108[22]: 381-9).
The press release actually contained a link to a pdf file of the article (full reference and link below).
Negative-pressure wound therapy (NPWT), also known as vacuum assisted closure,  involves covering the wound with an an airtight film and an adjustable negative pressure is applied using an electronically controlled pump.  The vacuum or negative pressure drains wound exudate.   NPWT is used for chronic persistent wounds and complicated wounds.
The article by Peinemann and Sauerland is a systematic review of the literature (English and German), aimed at  evaluating wound healing and adverse events following NPWT in comparison to conventional treatment in patients with acute or chronic wounds.  From the beginning summary:
We found reports of 9 RCTs in addition to the 12 covered by earlier IQWiG reviews of this topic. Five of the 9 new trials involved NPWT systems that are not on the market. The frequency of complete wound closure is stated in only 5 of the 9 new reports; a statistically significant effect in favor of NPWT was found in only two trials.The results of 8 of the 9 new trials are hard to interpret, both because of apparent bias and because diverse types of wounds were treated.
Data analysis used complete wound closure as the primary endpoint.  This was based on the U.S. Food and Drug Administration’s (FDA) 2006 Guidance for Industry definition for complete wound closure as “skin closure without drainage or dressing requirements.”
The following dependent variables were used as secondary endpoints:
● Adverse events, such as death, secondary amputations, fistula formation, and wound infection
● Time to complete wound closure
● Reduction in wound size
● Health-related quality of life.

In the discussion section of the article, some key summaries:
Regarding the primary endpoint of “wound closure” – results were not homogenous.  The authors notes it is currently impossible to be sure that NPWT performs better than control treatments.
Regarding the secondary endpoints
– Most articles reported “time to wound closure”  occurred quicker in NPWT groups.  The authors note “However, there were considerable differences between trials in terms of the methods used to measure and evaluate wound closure; particularly problematic is the fact that no blinding was used when this endpoint was measured.”  So for now, as with the  primary endpoint, it remains undecided.
--  The results on adverse events were not homogenous and varied depending on the specific complications.   For a number of other adverse events no statistically significant difference was detected.
The authors note that most trials of NPWT were conducted in hospitals.  They make this point in regard to the FDA report (3rd reference below):
The FDA recently issued a report on six deaths and 77 other complications that were reported within a two year period in connection with NPWT . All the deaths were caused by acute hemorrhages, and known contraindications for NPWT (e.g. a large blood vessel
exposed) had clearly been overlooked. Many of the deaths occurred in outpatient care or care homes, which highlights the need to monitor therapy.
The authors conclusion:
Although NPWT may have a positive effect on wound
healing, there is no proof that it is either superior or inferior to conventional wound treatment. Further RCTs of good methodological quality are required.

Peinemann F, Sauerland S: Negative pressure wound therapy—systematic review of randomized controlled trials; Dtsch Arztebl Int 2011; 108(22): 381–9; DOI: 10.3238/arztebl.2011.0381
An introduction to the use of vacuum assisted closure by Steve Thomas, PhD--World Wide Wounds (Last updated: May 2001)
FDA: Serious complications associated with negative pressure; 2009 (last updated 02/24/2011)

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