Negative pressure wound therapy improves treatment of soft tissue injury blast infection.

Image: CC 

Key study points:

1. Regulated negative pressure therapy (RNPT) reduced bacterial load compared to gauze dressings.
2. RNPT induced granulation tissue formation earlier than gauze dressings.
3. RNPT did not alter the aerobic and aerobic bacterial composition of wounds.

Primer:  Wound management has, for many years, relied on gauze dressings and frequent dressing changes to minimize the worsening of infection.  Only since the 1990s has the advent of negative pressure therapy for wound healing become relevant, with an increasing list of indications that now span everything from acute to chronic wounds.  In the Iraq war, blast injuries comprise about 80% of combat-related injuries, and, given the myriad of foreign bodies, have a high likelihood of developing infection.  This study focused on simulating the soft tissue blast injuries in pigs to assess the efficacy of different levels of negative pressure wound therapy as compared to gauze dressings.

Background reading:

1. Pirela-Cruz MA, Machen MS, Esquivel D. Management of large soft-tissue wounds with negative pressure therapy-lessons learned from the war zone. J Hand Ther. 2008;21:196–202;quiz 203.

This [randomized] study: 28 pigs were obtained for this study, with each receiving a small blast injury to each hip (56 in total).  The pigs were then randomized into 7 groups after 2 days of injury to allow infection to develop. One group was to receive gauze dressings changed multiple times per day, and the other six groups to be placed on RNPT.   Under RNPT, wound area and depth decreased significantly in the -10 to -25 kPa groups in comparison to the gauze group (p < 0.05). No tissue necrosis developed in the RNPT groups, whereas when the necrotic area increased in the gauze group, some of it was due to infection.  RNPT also decreased the wound closure time:  gauze pads took ~26.6, RNPT at any pressure level never took more than ~24.1 days, with most groups in the 19-21 days range on average (p < 0.05 vs. gauze).   In terms of bacterial load, the -10 to -35 kPa RNPT helped decreased the aerobic bacterial load to 10⁶ and 10⁵ after 1 and 6 days of treatment.  For gauze dressings, it took 6 and 14 days, respectively.  In the process of reducing bacterial load, the RNPT did not alter the ratio of aerobic to anaerobic bacteria.  Finally, with regard to granulation tissue formation, there were also significant differences, with the -15 kPa group observing granulation tissue after 1 day, and the gauze group only after 8 days.

In sum: This randomized study reasserts on multiple levels that RNPT can be particularly effective at dealing with complicated wounds.  Blast injuries have been the major type of injury in the Iraq war, and can particularly benefit from such treatment because of their high likelihood of developing infection.  This paper provides strong evidence to suggest that it can decrease time of wound healing, increase the rate of granulation tissue formation, minimize necrotic tissue formation, and reduce the overall bacterial load.  One limitation in this study is that it was completed in pigs, and level of differences seen when treated with RNPT in pigs may be different than that in humans.  Nonetheless, assuming that the physiology isn’t strikingly different, it would be reasonable to expect the results in humans to be similar and statistically significant.

Click to read the study in [Annals of Surgery]

By [DM] and [AH]

© 2012 2minutemedicine.com. All rights reserved. No works may be reproduced without written consent from 2minutemedicine.com. DISCLAIMER: Posts are not medical advice and are not intended as such. Please see a healthcare professional if you seek medical advice.