Diabetes mellitus is a major risk factor for the development of cardiovascular disease, including peripheral arterial occlusive disease (PAOD) or peripheral arterial disease. Approximately 20% of the 12 million Americans identified in the Framingham Heart Study as having symptomatic PAOD were diabetics. 1 However, this estimate may be low.
Nurse practitioners must be able to identify PAOD and initiate treatment quickly.
Experts believe over one-half of diabetic patients with PAOD are asymptomatic, approximately one-third have claudication, and the remaining patients have extremely severe symptomatic disease. Claudication is defined as intermittent pain, cramping, or aching in the lower extremities that occurs when walking, and is relieved by rest. Severe disease may present as resting claudication, gangrene, and need for amputation. Severe disease is also termed "critical limb ischemia." The greatest risk factors for the development of PAOD include smoking and diabetes mellitus. African Americans and Hispanic diabetics have the greatest risk. Other risk factors include aging, hypertension, hyperlipidemia, and duration of diabetes greater than 10 years.
PAOD in Diabetics
Peripheral arterial occlusive disease in diabetic patients is a major risk factor for lower extremity amputation and yet, to date, there are no guidelines for the prevention, identification, and treatment of PAOD in diabetic patients. Twenty percent of diabetic patients older than 40 years of age have PAOD and 29% of diabetic patients over 50 years of age have PAOD. Twenty-seven percent of diabetic patients with PAOD will have disease progression within 5 years; 4% of those patients will require amputation, and 20% will experience nonfatal cardiovascular events such as myocardial infarction or stroke. 1 In patients with chronic limb ischemia, 30% will have amputations and 20% will die within 6 months. 1
In 2003, the American Diabetes Association developed a consensus statement addressing the issue of PAOD in the diabetic patient. The full consensus statement can be found in the December 2003, issue of Diabetes Care or online at http://www.care.diabetesjournals.org/egi/content/full/26/12/3333. 1 Since diabetes is one of two major risk factors for the development of PAOD and because over one-half of diabetic patients may have the disease but be asymptomatic, it is imperative that nurse practitioners have a strong suspicion of PAOD in diabetic patients and the ability to identify the disease and initiate treatment quickly.
Identifying PAOD
In the past, identification of PAOD was done by clinically analyzing reported symptoms of claudication or absence of palpable peripheral pulses. However, these methods are insensitive and may not identify patients early enough. A more sensitive test is the ankle-brachial index (ABI). The ABI is obtained by measuring systolic blood pressures in the ankles and arms via a Doppler and then calculating a ratio between the two. When compared to angiographically determined arterial disease, measuring ABI is 95% sensitive and almost 100% specific. 1 However, sensitivity decreases in the elderly and in some diabetic patients who have artificially elevated pressures. Calcified, poorly compressible vessels, and vessel stenosis in these patients account for potential inaccuracies.
Evaluation
Evaluation of the potential PAOD patient includes a detailed history and physical examination. The history should include ambulation. The physical exam should concentrate on potential PAOD findings such as dependent rubor, pallor with elevation, absence of hair growth on the lower extremities, dystrophic toenails, cool and dry skin, and weak or absent pedal pulses. Examination of pulses of the lower extremity should include the femorals and popliteals, as well as the pedal pulses. After taking the history and completing the physical examination, calculate the ABI.
To correctly perform the ABI, place the patient recumbent for 5 minutes. Next, measure the systolic blood pressure in both arms and use the higher value for the brachial portion of the index. Then, measure the systolic blood pressure in the ankles using the dorsalis pedis and posterior tibial arteries. Place the blood pressure cuff just above the ankle and use a Doppler for ascertaining the systolic blood pressure. As with the brachial portion, use the higher ankle systolic pressure value. Divide the brachial reading into the ankle reading to get the ABI (see Table: "Ankle-Brachial Index").
Other Tests
In patients who have poorly compressible arteries or in patients who warrant follow-up, additional testing should be ordered. Potential additional tests include vascular evaluation, treadmill testing, duplex sonography, magnetic resonance angiography, x-ray angiography, and transcutaneous partial pressure of oxygen. Vascular lab evaluation includes segmental pressures and pulse volume recordings at the toe, ankle, calf, low thigh, and high thigh. The values help to determine vessel lesion location. Treadmill testing can illicit claudication symptoms and can also determine if the treatment for PAOD is working. Sonography and magnetic resonance imaging can identify specific lesions and/or blood vessel wall abnormalities and invasive angiography can be useful prior to surgical procedures such as angioplasty.
Testing diabetic individuals for PAOD should be considered, along with the normal vital signs of blood pressure, heart rate, respiratory rate, and temperature. Smoking is also a major risk factor, so a smoking history should be obtained at each visit. In diabetics, feet are evaluated at every visit. Peripheral arterial occlusive disease screening should be done in all diabetics by the age of 50 years, and in younger diabetics with risk factors such as smoking, hypertension, hyperlipidemia, or diabetes for longer than 10 years. Screening is done using the ABI. In patients with a normal ABI, a rescreen should be done in 5 years. In patients with abnormal ABI measurements, treatment should be initiated and rescreening done on a reduced schedule. It may be helpful to complete an ABI at least on a yearly basis, along with checking for microalbuminuria.
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