OTTAWA — The ankle-brachial index, which indicates the arterial supply to the legs, can help confirm an arterial wound in suspected cases of arterial leg ulcers, Dr. Rob Miller said at the annual conference of the Canadian Association of Wound Care.
Identification of atherosclerosis is often delayed because the wounds are insidious; 50%–70% of the artery's interior must be blocked before the tissue breaks down and wounds appear, said Dr. Miller, a dermatologist at Queen Elizabeth II Hospital in Halifax, N. S.
“The ankle-brachial index is the most effective and practical way to check for arterial disease,” Dr. Miller said. An ankle-brachial index (ABI) test requires measuring the blood pressure in both the ankle and the arm of the patient at rest, and dividing the ankle systolic pressure by the brachial systolic pressure. Blood pressure should be rechecked after the patient completes a 5-minute treadmill test. An ABI of 0.9 mm Hg or less after activity is predictive of arterial disease, and the ABI has a specificity of nearly 100% in identifying individuals without arterial disease, Dr. Miller noted.
Clinical features of arterial wounds include delayed capillary refill time, in which a toe takes more than 3 seconds to regain normal color after being gently squeezed, and Buerger's sign, in which the foot turns pale when elevated by 30 degrees and becomes red when lowered. Other signs are dry, scaly skin, soft tissue atrophy, and a lack of hair in the area of the ulcer.
ABI also may predict limb loss. Dr. Miller cited a recent study of 142 patients and 169 limbs in which chronic leg ulcers were treated with pressure relief, debridement, infection control, and moist healing. These patients could not be treated with revascularization surgery due to comorbidities and other risk factors (J. Vasc. Surg. 2006;44:108–14). Patients with ABI measurements less than 0.5 mm Hg were significantly more likely to have a limb amputated after 6 months (28%) and 12 months of treatment (34%), compared with patients with ABIs higher than 0.5 mm Hg (10% and 15%, respectively).
The treatment strategy depends on how much fluid can pass through the arteries. If perfusion status is adequate, the wound can be debrided and dressed. If perfusion status is marginal, conservative treatment consisting of minimal, judicious debridement and dressing is indicated and should be followed with a referral to a vascular surgeon if the wound isn't healing. If perfusion status is inadequate, make a referral to a vascular surgeon, Dr. Miller advised.
Surgical revascularization is the mainstay of treatment for most arterial ulcers because pharmaceutical and medical interventions have not matched its efficacy. But not all patients are candidates for surgery, and consequently the ABI measurement can help assess which of these patients who are medically managed are more likely to need amputations.
Medical management of arterial ulcers involves treating the underlying medical problems and providing proper wound care. Strategies include lipid-lowering therapy, control of hypertension and diabetes, exercise, and topical vasodilators. Avoid excessive debridement of arterial ulcers. Instead, paint the area with a povidone-iodine mix. And don't use compression therapy, because it exacerbates ischemic disease and is contraindicated for arterial ulcers.
In one study, patients with index measurements less than 0.5 mm Hg were significantly more likely to have a limb amputated after 12 months of treatment (34%), compared with patients who had index values higher than 0.5 mm Hg (15%). Courtesy Dr. Rob Miller