Chemical debridement can be an alternative
Here’s the story on enzymatic debridement agents
T he jury is still out on the effectiveness of chemicals for debridement, but some experts are finding that in certain situations it offers a good alternative to other methods. This is especially true when patients refuse surgery, when surgery is contraindicated, or when an occlusive dressing isn’t expected to heal a wound quickly enough.The goals of all debridement techniques essentially are the same — to remove devitalized tissue and reduce bacterial contamination — and each approach has advantages and shortcomings. Mechanical debridement (such as wet-to-dry dressing changes) is simple, inexpensive, and often effective. Yet this method:
• may take a long time before results are realized;
• can cause pain when dressings are removed;
• has been implicated in disrupting newly formed granulation tissue.
Surgical debridement is fast but can destroy surrounding viable tissue and result in inadvertent enlargement of the wound and extension of existing infections, according to Mary Lynn Moody, RPh, director of drug information at Columbia Michael Reese Hospital in Chicago and clinical assistant professor at the University of Illinois College of Pharmacy.
Chemical debridement is still somewhat controversial because clinical studies to gauge its effectiveness are scarce. In addition, chemical debridement can be very time consuming. It is used most commonly for stage II ulcers but can be used for advanced stage I and early stage III ulcers. Wounds that progress to stage III usually require surgical debridement, Moody explains.
The enzyme family
The most common chemicals used for wound debridement are enzymes that digest necrotic tissue, referred to as enzymatic debridement agents (EDAs). Arguably, the most well-known EDA is collagenase (brand name Santyl). Collagenase is also considered by many clinicians to be the most effective member of the enzyme family, Moody says.Collagenase dissolves undenatured collagen fibers, which anchor necrotic tissue to the surface of the wound, without damaging granulation tissue. It is most effective when surrounding pH ranges from 6 to 8, Moody explains; therefore, non-acidic detergents and antiseptics should be used to clean wounds prior to collagenase debridement.
Hexachlorophene and benzalkonium chloride are acidic and will adversely affect the action of collagenase, as will antiseptics containing heavy metal ions such as mercury and silver. "Normal saline is usually best for cleaning the wound in these cases," says Moody. Dakin’s solution and hydrogen peroxide are also compatible with collagenase.
The potential side effects of collagenase include skin irritation, inflammation around the edge of the wound, burning pain on the skin, and paresthesia where the ointment is applied. Occasionally, some bleeding caused by the dissolving of healthy skin occurs. It is this latter side effect of collagenase that concerns Lawrence Kollenberg, DPM, medical director of the Garland Count Foot Clinic in Hot Springs, AR, and a licensed pharmacist.
Kollenberg has worked with EDAs for about 14 years and takes exception to the contention in the collagenase entry of the Physicians’ Desk Reference that says the chemical does not attack healthy tissue. "It eats everything: necrotic tissue and healthy tissue," he says. "Because of its nonselectivity, collagenase acts to stop new fibroblasts from forming."
The low selectivity of collagenase is less of a concern for Robert S. Kirsner, MD, assistant professor of dermatology at the University of Miami School of Medicine and co-director of the Cutaneous Ulcer Rehabilitation and Education program at Columbia Cedars Medical Center in Miami. "Usually selectivity isn’t important to me because my next step is often going to be surgery, which is obviously not very selective," he says.
"During surgery, some normal tissue is going to be damaged. The idea of debridement is to get rid of bad tissue. It’s a very specific goal, and stimulation of granulation tissue is a secondary consideration," Kirsner says. "Theoretically, if you could selectively rid yourself of just necrotic tissue, that would be advantageous, but in a clinical situation, I haven’t found it to make that big a difference." Kirsner uses chemical debridement on a limited basis, preferring mechanical and surgical techniques.
More selective
Among the more selective EDAs is sutilains (brand name Travase), a proteolytic enzyme ointment that digests necrotic tissue and minimally digests collagen and healthy tissue, Moody says. Enzymatic activity becomes optimal in the very narrow pH range from to 6.8, therefore, the same precautions taken when selecting wound cleansing and disinfecting solutions for collagen apply to sutilains. Sutilains can cause burning pain, paresthesia, transient dermatitis at the application site, and occasional bleeding. Loose, wet dressings over the ointment are the best environment for this agent. Complete dressing changes should be repeated every six to eight hours, Moody advises.A third type of EDA, papain urea agents, include the drugs Accuzyme and Panafil. These also are selective agents that digest nonviable protein matter but are harmless to viable tissue, Kollenberg says. They also have the advantage of being active over a wide pH range (3 to 12). "They act on necrotic tissue present in the wound and debride only that tissue that needs to be debrided, so they don’t interfere with fibroblastic proliferation," he explains.
Two other EDAs, Elase (a combination of fibrinolysin and desoxyribonuclease) and Granulex (a combination of trypsin, balsam peru, and castor oil), are still available but not widely used, says Kollenberg, who emphasizes that chemical debridement should be used as an adjunct to, not a substitute for, other methods of debridement.
In a category of its own is the debridement agent dextranomer (brand name Debrisan), which is described as a "collagen absorbable hemostat." Dextranomer consists of spherical hydrophilic beads 0.1 to 0.3 mm in diameter that absorb wound exudate via molecular and capillary action. The beads swell to approximately four times their original size, which causes significant suction and capillary action in the spaces between the beads.
When dextranomer is wiped out of the wound with a gauze pad, Moody says, the friction of the beads against tissue also helps to break up some necrosis. It also appears to increase tissue granulation, decrease wound inflammation, and decrease pus and debris, she adds.
Clinical data are scarce
Dextranomer is chemically inert and has no chemical effect on wounds. According to the Physicians’ Desk Reference, each gram of dextranomer beads absorbs approximately 4 ml of fluid. A paste form is available for application on irregular body surfaces or hard-to-reach areas. Dextranomer is indicated for use in cleaning wet ulcers and wounds such as venous stasis ulcers, pressure ulcers, infected traumatic and surgical wounds, and infected burns. A less attractive feature of dextranomer is its relatively high cost. In addition, very little hard clinical data on its use is available.Moody explains that before the application of dextranomer, the wound should be cleaned and left moist. Dry dextranomer beads are then packed into the wound to a depth of one-fourth of an inch or greater and covered with gauze. The material should be removed and reapplied two to three times a day. Application and removal of dextranomer have reportedly caused isolated cases of transitory pain, bleeding, blistering, and erythema. Debrisan should be discontinued when the wound becomes dry and a healthy base of granulation tissue has been established.
Whatever chemical agent is chosen, it should be patient specific and patient selective, says Kollenberg. If a patient exhibits any form of adverse reaction to the chemicals being used, the chemicals should be discontinued immediately. n
The effects of common debridement agents
Collagenase• enzymatic debridement ointment
• widely considered to be very effective
• dissolves undenatured collagen fibers
• nonselective, dissolves viable tissue
• effective pH range: 6 to 8
• avoid acidic solutions for wound cleansing
• avoid medications with salts of heavy metals
• Dakin’s solution and buffered normal saline will not inhibit enzymatic activity
• generally applied once daily (unless extremely soiled wound)
• may cause irritation, inflammation of normal skin at wound edges
Sutilains (brand name Travase)
• enzymatic debridement ointment
• selectively digests necrotic tissue
• minimal collagen digestion
• use with loose, wet dressing; keep moist
• repeat dressing process every six to eight hours
• effective pH range: 6 to 6.8
• avoid acidic solutions for wound cleansing
• avoid medications with salts of heavy metals
• may cause burning pain, paresthesia, transient dermatitis at application site, occasional bleeding
Papain Urea (brand name Panafil)
• enzymatic debriding ointment
• harmless to viable tissue
• effective pH range: 3 to 12
• daily or twice daily dressing changes recommended
• medications with salts of heavy metals may inactivate the ointment
• may cause transient burning sensation on application
Dextranomer (brand name Debrisan)
• inert compound composed of microscopic beads
• available in dry or paste form
• used to clean and debride wounds
• works by molecular and capillary absorption
• may increase tissue granulation and decrease inflammation
• replace beads two to three times a day
• removal may cause intermittent pain, bleeding, blistering and erythema.
• no major adverse reactions reported n
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