In 1975, hydrocolloid dressing was introduced to absorb exudates forming a moist gel on the surface of the wound. The moist gel maintains the moist and warm wound environment suitable for growth of the granulation tissue, controls wound infection, increases rate of epithelialization and reduces pain.
Negative pressure dressing using an adhesive polyurethane film (OpSite) and suction bottle, as advised by Singh et al, is cost effective and can be adjuvant management of chronic infected wounds. Though doubts have been raised recently, topical negative pressure applied over the wound surface is supposed to increase circulation and granulation tissue, and decrease the bacterial count in the wound.
The conventional negative pressure dressing described by Mullner et al has the disadvantage of no access to the wound for the surgeon to daily irrigate the wound with local anti-microbial agent of his choice like that in LAD. However, Silverlon® (Argentum Medical, Willowbrook, Ill) that continuously emits a very high level of ionic silver into the wound bed may be placed under negative pressure dressing for better infection control for 1 week. The second tube of the LAD is help-ful in changing the wound environment and to some extent guards against the problems of tube blockage due to thick secretion and slough.
Others[25,26,42,43] have used topical negative pressure foam dressing with continuous suction between 50 mmHg-125 mmHg.With LAD as low as 30 mmHg, topical negative pressure produces satisfactory results (see Results section).
In LAD II, the bad odor was attributed to chemical (present in the wound and body secretion) degradation of nonviable tissue, discharge and degradation of shed surface epithelium.The problem of odor was reduced by daily saline LAD wash.To reduce the smell at the time of removing the LAD,multiple punctures were made in the polythene sheet and tubes were connected to wall suction (central suction) for 5 minutes.
Consistently better graft take under LAD appeared to be due to control of infection and intermittent compressions of graft between polythene sheet and recipient area, which squeezes any collection under the graft and removed by the suction.Téot et al, recently reported a strong correlation between the positive clinical effects of the VAC system and high levels in the wound of proangiogenic growth factors, such as vascular endothelial growth factor (VEGF).[44,45] High VEGF may also be responsible for better graft take.
In LAD IB and LAD II, the wound is covered with a polythene sheet that is not permeable to water vapor. In these designs the moisture was removed intermittently along with secretions by negative suction. LAD was also useful to keep the exposed tendons and periosteum viable by providing moist environment until definitive cover is provided. The pus like gel (usually a source of concern to the patients) produced due to combination of hydrocolloid material and wound secretion in hydrocolloid moist dressings was absent in LAD.The negative pressure appears to provide a competitive alternate negative channel for lymphatics and venules (channels for bacterial invasion), therefore, instead of invading the tissue, microorganisms under influence of negative pressure are directed towards the suction bottle for safe disposal.
In the present study, the average number of days required to prepare the wound under LAD was 17.05. Overall graft take under LAD was 99.87%.Twenty-four of 39 wounds (24/39) on an average 33.83 days with conventional dressing (range 7 to 120 days; median 22.5 days) did not achieve healthy granulation fit for skin grafting, but when switched to the LAD,wound preparation took an average of 13.2 days (range 3 to 32 days; median 12 days).
Overall, the LAD was found to be a safe and effective alternative to conventional dressing methods.
LAD application was easy and retained all the advantages of moist wound healing and negative pressure dressings and avoided all of their disadvantages by manipulating the wound environment by providing limited access through tubes.
Wounds. 2008;20(2):49-59. © 2008 HMP Communications
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Cite this: Limited Access Dressing - Medscape - Feb 01, 2008.