Acute limb ischemia (ALI) is a limb-threatening condition that is a true surgical emergency as delays over 6 hours are associated with limb loss or permanent loss of function. Chronic limb ischemia is also an emergency, but less so as collateral circulation is often present that can mitigate additional ischemia. Both conditions are often diagnosed late because they can mimic a number of other more common conditions that cause leg pain or weakness.

To accurately assess and diagnose this condition, the clinician needs to eliminate other possible diagnoses such as sciatica, deep vein thrombosis (DVT), stroke, and ankle sprain as the leg weakness can cause secondary falls. For example, DVT typically presents as redness and swelling in the lower limb but not mottling or darkening of the skin. Cellulitis also causes redness but not mottling or darkening of the skin. An electrolyte abnormality would cause diarrhea because of low potassium levels but the lower limbs usually are not affected.

Acute limb ischemia is usually caused by embolism and more rarely can be caused by aortic dissection or knee dislocation. Cancer and chemotherapy may predispose patients to acute limb ischemia. The clinical presentation of ALI typically involves some combination of pain, numbness, weakness, cold, and/or discoloration. This discoloration is typically pallor but may be darkening or, in some cases of chronic ischemia, dependent rubor that can look cellulitic. Warmth or swelling are not typically present and if seen would be suggestive of DVT or infection. Pulses are typically diminished but may feel symmetric in milder cases. The foot is typically cooler as well, but not always.


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If ALI is suspected, an ankle-brachial index should be measures at the bedside as soon as possible. This is calculated as the systolic BP in the ankle divided by that in the arm. A normal value is >0.9 and a value <0.5 signifies severe ischemia. Diagnostic testing for ALI should include arterial duplex ultrasound, computed tomography angiogram, or both.

Workup to determine the cause of the embolism may include radiographs of traumatic injury, electrocardiogram, echocardiogram, or CT angiogram of the aorta. An elevation in creatinine kinase may be an early clue of more severe disease and at-risk muscles.

Treatment should be initiated immediately once the diagnosis is established, or sometimes earlier if severe disease is strongly suspected. This treatment may include consulting vascular surgery and/or interventional radiology for definitive care and aspirin and/or heparin for temporizing care.

The patient in this case was referring to interventional radiology and underwent thrombolysis of acute limb ischemia.

Brady Pregerson, MD, is an emergency physician at Tri-City Medical Center in Oceanside, California and at Scripps Coastal Urgent Care in Oceanside, California.

Reference

Pregerson DB. Vascular surgery: limb ischemia. In: Emergency Medicine 1-Minute Consult Pocketbook. 5th ed. 2017;5:343. https://em1minuteconsult.com/?page_id=1227