Gordon Dow, M.D., FRCPC
Section of Infectious Diseases, Department of Internal Medicine
The Moncton Hospital,
Moncton, NB

Wound Care
Although measures to optimize perfusion to the affected limb and displacing and minimizing mechanical forces at the effected area are critical to expediting healing of a diabetic foot ulcer, wound care is an important adjunctive measure. Wound care can be summarized as follows:

Local Debridement
Wound debridement is an essential aspect of local wound care. All non-viable tissue acts as a foreign body which promotes bacterial proliferation and wound deterioration. Sharp surgical debridement has been proven to accelerate wound healing and should be aggressively and frequently carried out, except in the setting of wound ischemia, where this process should be minimized until tissue revascularization is accomplished.²

Chemical Debridement
Chemical debridement has been less well studied. The most commonly used chemical debriding agent is the Edinburgh University Solution Of Lime (EUSOL) which is a calcium hypochlorite solution containing <.25% w/v available chlorine, usually administered as a half-strength wet to dry solution three to four times per day. This agent has come under significant criticism for potential injury to underlying viable tissue. However there is currently no firm clinical data to prove that this agent delays wound healing when used appropriately.³ In light of the controversy surrounding this agent, it should be applied only by those familiar with its use for necrotic wounds where aggressive sharp debridement leaves residual necrotic material due to technical difficulties or is contraindicated.

Enzymatic Debridement Agents
These have an uncertain role, the two most common available agents being collagenase, and a combination of papain and urea. Unfortunately there is inadequate randomized clinical trial data to define the role for these agents.

Mechanical Debridement
This is generally carried out by saline wet to dry dressings. There are many disadvantages to this which include injury to normal tissue, pain and the necessity for frequent dressing changes. Saline wet to dry dressings should be used only on a short term basis and restricted to infected necrotic wounds.

Autolytic Debridement
This technique involves the use of dressings which permit a moist wound environment so that host neutrophils and macrophages will clear away all devitalized tissue. This is an excellent means of wound debridement but is slow and should not be used in infected wounds.

Maggot Therapy
The beneficial effect of maggot therapy for debridement of diabetic foot ulcers has now been demonstrated and was first described by Baron Larrey, physician-in-chief to Napoleon's armies.⁴ It is largely used for wounds that cannot be debrided by other means. Depending on the size and depth of the wound, 50-1,000 sterile maggots, approximately 24-48 hours old, are applied two to four times per week and left on for a period of 24-72 hours. A two-week course is successful for most patients with diabetic foot ulcers. While this appears to be an exceedingly effective means of debriding difficult wounds, maintaining a supply of sterile maggots and the obvious aesthetic drawbacks of this form of therapy will limit its use until better randomized trials become available.

Irrigation
Wound irrigation has been shown to accelerate the rate of healing of chronic wounds and probably does so by removing bacteria and adherent proteinaceous tissue exudates which can act as a foreign body. Irrigation pressure should likely be maintained between 8-15 psi as pressures below that range are likely less effective while pressures exceeding that range may be injurious. Pressure in this range can be achieved by using a 20 ml syringe with an 18 gauge plastic angiocatheter. Under most circumstances, saline solution is a sufficient irrigant. This can be made by adding 2 tsp. of salt to 1 litre of boiling water for home care use. Although there are numerous wound cleansers on the market with surfactant activity in the irrigating solution, these do have some increased tissue toxicity compared to saline. Their role should be limited to those wounds with excess necrotic debris rather than a wound with healthy granulation tissue.

Wound Disinfectants
There is currently no evidence to support the use of disinfectants either for wound irrigation or in wet to dry dressings. This would particularly apply to hydrogen peroxide, povidone, and various alcohols. These agents have been shown to have minimal impact on reducing bacterial counts within a wound, damage host tissue, delay wound healing and increase the rate of wound infection.⁵ There is a growing body of evidence to suggest that short term use of acetic acid (vinegar) in a dilute solution may be an exception to this rule concerning disinfectants.⁶ Lowering the pH on the surface of a wound has been demonstrated to accelerate wound healing. A dilute vinegar and water solution is also a superb means of eradicating local Pseudomonas sp. wound infection. It likely has similar activity against gram negative rods and anaerobic flora, and consequently can improve odor control. It should therefore be considered as an irrigating solution or a foot soak in infected necrotic wounds, particularly if associated with Pseudomonas sp or anaerobic flora. A commonly used dilution is 15 ml of 5% vinegar per 250 ml of water or saline. A foot soak should not exceed 10-15 minutes.

Although iodine containing disinfectants are generally detrimental to wound healing, Codexomer iodine ointment or paste is a safe product which absorbs wound exudate and decreases superficial bacterial burden.

A variety of silver impregnated dressings are currently available. These also are capable of reducing bacterial burden on the surface of a wound without injuring granulation tissue.

Wound Dressings
There has been a massive proliferation of advanced wound dressings in Canada over the past ten years with the result that there are now hundreds of different dressings to choose from. The available literature suggests that these advanced dressing materials are more convenient, comfortable and cost-effective in comparison to saline moistened dressings, but have not been convincingly shown to dramatically increase the rate of wound healing (except for superficial ulcerations). Because of this vast array of products, it is often beneficial to have a wound care expert participate in the management of diabetic ulcers. What is placed on a wound is far less important than the primary measures of pressure relief and treatment of ischemia. If a wound is infected and exudative there is still a role for saline wet to dry dressings or the use of salt-impregnated gauze packings. For wounds that are not infected but still contain a great deal of excess exudate, then an absorptive dressing such as a fiber or foam dressing may be used. Alginate dressings are useful post debridement to assist hemostasis and absorb exudate. Topical hydrogels are very effective for wounds that are not exudative or infected and are usually applied on a once daily basis. There is inadequate evidence of benefit for hydrocolloids to recommend their use for most diabetic foot ulcers.

Global Patient Care
While local wound care, as described above, is of importance, diabetes is a systemic disease with multiple associated comorbidities, and these should all be addressed in a patient with an active diabetic foot ulcer. All patients should have optimization of glycemic control. Impaired glucose control has been associated with impaired wound healing and increased infection. Blood pressure should be well-controlled in all patients; angiotensin converting enzyme inhibitors are the agents of choice in this population. As the primary cause of death for persons with a diabetic foot ulcer is cardiovascular disease, all patients should undergo aggressive lipid-lowering therapy and should be given once-daily aspirin and smoking discontinuation advice. Perfusion pressure in the diabetic extremity ulcer should be optimized, particularly in the setting of ischemia. Not only does this involve revascularization, but should also include treatment of underlying heart failure, mobilization of edema and avoidance of tight-fitting hosiery and footwear.

Hyperbaric Oxygen Therapy (HBOT)
There have been seven studies evaluating the use of HBOT for diabetic foot lesions, two of which were randomized controlled trials.⁷ In both of these latter trials, there was a significant reduction in the rate of major amputation. This benefit appears most apparent for the sub-group with full-thickness gangrene (Wagner Grade IV Lesions). Given the high cost of this procedure, uncertain criteria for patient selection and limited scientific evidence, it should be offered primarily for patients with severe grade IV lesions, and hopefully a large randomized multi-center trial will further clarify its role. HBOT should not be used as a replacement for aggressive surgical revascularization, particularly as severe ischemia reduces the efficacy of HBOT. Topical oxygen therapy is not HBOT and has not been shown to improve wound healing in diabetes.

Summary
Multiple adjunctive measures are available to supplement management of diabetic foot ulcers. These measures are both local (wound irrigation, debridement, advanced dressings) and systemic (glycemic control, blood pressure control, lipid management, anti-platelet agents, smoking discontinuation, control of edema/heart failure and HBOT). Because of this wide range of adjunctive measures, management of diabetic foot ulceration requires a multidisciplinary approach.

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