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Peripheral arterial disease is defined as an ankle-brachial index (ABI) of <0.9 (see ABI definition below). The disease prevalence is 4.3% in Americans under age 40 years; prevalence climbs to 15.5% in those over 70 years of age. High-risk individuals (such as those over 70 years, or those over 50 years with risk factors such as diabetes or tobacco use), should be evaluated carefully when complaints are indicative of possible occlusive arterial disease. This time-sensitive condition can lead to irreversible changes in peripheral nerves and skeletal muscle tissue in 4 to 6 hours. The most frequently involved arteries, in descending order, are the femoropopliteal, tibial, aortoiliac, and brachiocephalic.
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Patients with acute arterial limb ischemia typically present with one of the “six Ps”: pain, pallor, poikilothermia (coldness), pulselessness, paresthesias, and paralysis. Pain is the earliest symptom and may increase with elevation of the limb. Changes in skin color with mottling, splotchiness, and cool temperature are common. One of the early signs of ischemic limb pain may present as muscle weakness. Limb viability may be in question when there is acute anesthesia progressing to paralysis. A decreased pulse distal to the obstruction is an unreliable finding for early ischemia, especially in patients with peripheral vascular disease and well-developed collateral circulation. Claudication refers to a cramplike pain, ache, or tiredness that is brought on by exercise and relieved by rest. It is reproducible, resolves within 2 to 5 min of rest, and reoccurs at consistent walking distances. The pain of acute limb ischemia is not well localized, is not relieved by rest or gravity, and can be a worsening of chronic pain (if it is caused by a thrombotic event).
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Diagnosis and Differential
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Although thromboembolic disease is the most common cause of acute arterial occlusion, the differential diagnosis may include: catheterization complications, vasculitis, Raynaud disease, thromboangiitis obliterans, blunt or penetrating trauma, or low-flow shock states such as sepsis. Most commonly, a history of an abruptly ischemic limb in a patient with atrial fibrillation or recent myocardial infarction is strongly suggestive of an embolus. A history of claudication suggests a thrombosis.
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For more objective testing, a handheld Doppler can document blood flow or its absence in the affected limb. Duplex ultrasonography can detect an obstruction to flow with sensitivity greater than 85%. In addition, the ABI can be easily measured in the emergency department. Using a blood pressure cuff, place a Doppler US at the brachial artery and record the pressure of occlusion. Repeat the procedure on the leg, measuring the occlusion pressure of the posterior tibial and dorsalis pedis arteries. The ABI is the leg occlusion pressure divided by the arm occlusion pressure; normal ABI is >0.9. With arterial occlusion with a blood pressure cuff, the ABI usually is markedly diminished with a ratio between 0.9 and 0.41. A ratio lower than 0.41:1 is usually found in limbs with critical ischemia. ...