Treating the wounded: New strategies in healing

Getty ImagesWe all want that magic wound-healing bullet-the one treatment or dressing or bandage to use on every wound on every patient. Sure would simplify things, wouldn't it? Unfortunately, wound healing is a complicated process and requires different approaches for optimal care. Fortunately, Emily Miller, DVM, DACVS, from the University of Missouri College of Veterinary Medicine, has laid it all out regarding what's new in wound care.

The 6 basic wound management steps

1. Prevent further contamination, such as nosocomial infections.

2. Débride necrotic tissue. Devitalized tissue incites inflammation, and as long as inflammation is there, the wound won't progress to the repair phase.

3. Remove foreign debris and contaminants-for the same reason as the necrotic tissue.

4. Ensure that the wound has adequate drainage.

5. Establish a healthy vascular wound bed. Healthy granulation tissue is essential!

6. Select appropriate methods of closing the wound if required.

Flourishing with fluid

Keep in mind that the goal for treating acute wounds is simple-to relieve any roadblocks to uncomplicated wound healing. In a nutshell, Dr. Miller says, “We want to do what we can to foster a happy, healthy wound environment to let this animal's body do its normal wound-healing thing.”

More and more these days that appears to be fostering a moist wound environment in early healing. For any wound that needs it, surgical débridement is a must, but autolytic débridement has recently been gaining ground, Dr. Miller says. This is the crux of moist wound healing. It's taking advantage of the body's own capability to débride wounds.

A note about exogenous enzymatic products

Exogenous enzymes can be used as an adjunct to lavage and surgical débridement. Most will spare healthy living tissues but can be irritating to local tissues. They can break down necrotic tissue, liquefy coagulated thick proteinaceous early wound fluid, and possibly break down biofilm of bacteria. They require contact time to work and each one is different (there is no data on which ones are considered more effective), so follow the manufacturer's recommendations for use and wound contact time.

No longer is wound fluid seen as the enemy. It contains endogenous enzymes that can selectively degrade necrotic tissue, inflammatory cells and phagocytes, Dr. Miller says. Cytokines and growth factors stimulate the formation of granulation tissue, angiogenesis and reepithelialization of the wound. And wound fluid also provides an ideal environment for phagocytosis to occur by providing optimal pH and oxygen tension.

Topical antimicrobials: a few of the old favorites

“For some reason, people really love to put things on wounds,” says Dr. Emily Miller. But nothing applied to a wound substitutes for proper wound management. Another major caveat? Very little scientific evidence exists for any topical product.

Triple antibiotic ointment.The zinc bacitracin in this combo enhances epithelialization but delays contraction. The ointment has broad-spectrum antimicrobial activity but is ineffective against Pseudomonas species. It is also better at preventing infection than treating an infection that's already established.

Silver sulfadiazine. This product also has broad-spectrum antimicrobial activity and is effective against some fungi as well. It has been the topical of choice for burn wounds because it can penetrate necrotic tissue, which many topical agents can't. Although it enhances epithelialization, it's toxic to keratinocytes and fibroblasts. In addition, it's hydrophilic, which means it promotes moist healing.

Nitrofurazone. This drug has broad-spectrum antimicrobial activity but little efficacy against Pseudomonas species. It's hydrophilic but delays epithelialization and is a known carcinogen.

Gentamicin sulfate. This is an appropriate choice when a wound is suspected to be infected with gram-negative bacteria. It also promotes epithelialization.

Patients that undergo autolytic débridement tend to be more comfortable at the wound site because it's not as painful as surgical or mechanical débridement, Dr. Miller says. However, the disadvantage is significant sometimes-this is a slow process. It may take a couple of days before it becomes noticeably effective.

New avenues of healing

While the old standbys are still around-and will be most likely for some time (see “Topical antimicrobials: A few of the old favorites”)-other approaches have been gaining attention recently. Here are a few.

Biosurgical débridement-AKA medical maggots! These creepy crawlers may make your skin crawl, but they may turn out to be very beneficial in wound management, Dr. Miller says. At the moment they're being studied more in human medicine than veterinary.

Wound-healing enhancers-sweet! These two wound-healing enhancers you'd expect to find in your kitchen rather than your wound-care arsenal.

• Honey. Some claim that honey enhances wound débridement, reduces edema (it's hypertonic to the wound, so it draws fluid out of surrounding tissues) and inflammation, promotes granulation and epithelialization, and has some antibacterial activity. Dr. Miller is reserving judgment. “There is no current data that this is doing better than other wound management strategies,” she says. “It sounds great, but is it actually working? I'm not sure.”

If you do use honey for treating wounds topically, Dr. Miller recommends unpasteurized medicinal grade honey. 

• Granulated sugar. Like honey, sugar's benefits seem to arise from its hypertonic character. It's purported to reduce edema, have some antibacterial properties, accelerate sloughing of any devitalized tissue and promote granulation of the wound. The main challenge? Experts recommend using a 1-cm-thick layer over the wound to be effective. Talk about messy!

Circling the drain? Another goal for wound-healing therapy is to provide adequate drainage. What's new here is … ready for it? Vacuum-assisted drainage! This technique uses open-cell sterile polyurethane foam that can be trimmed to the wound size. This is then sealed to the wound with an adhesive drape to which a vacuum is attached. The vacuum-generated pressure draws the wound fluid into a reservoir.

Applying subatmospheric pressure (negative 125 mm Hg to be exact) is thought to increase blood flow to the wound tissues, increase the speed with which granulation tissue forms and reduce microorganism numbers (although this effect has not been reproduced). A significant benefit is that this method of wound treatment allows for bandage changes every two days or so, depending on how exudative the wound is.

Bandages. So what's new in bandages? Two words: interactive dressings. These primary (closest to the wound) layers are semiocclusive and nonadherent. They're hydrophilic, helping create the desired moist healing environment, but can cause maceration of normal skin, so they should be applied only to the wound bed. Some can modulate cell activity and growth factor release. They are highly absorbent, which allows a longer time between bandage changes-and that's a beautiful thing. There are two getting attention right now:

• Calcium alginate. Made from seaweed, calcium alginate comes in ropes and sheets for different wound types. It stimulates granulation and epithelialization. Fair warning: When it's doing its job, over time it turns into a viscous, jelly-like substance against the wound and secondary bandage layer, so it needs to be rinsed off. It can be used during inflammatory and repair phases of healing. Depending on how exudative the wound is, bandage changes should occur every one to five days.

• Dr. Emily Miller and MarvinPolyurethane foam. This material is even more absorbent than calcium alginate, is comfortable for the patient, and promotes epithelialization and wound contraction. It conforms well to wounds and can be used as a filler in deep wounds. However, it can result in reduced granulation tissue formation. It also can be used in the inflammatory and repair phases of wound healing and again, depending on the amount of exudate a wound is producing, this dressing needs to be changed every three to seven days.