Patients with acute limb ischemia will exhibit one or more of the "six P's": pain, pallor, polar (for cold), pulselessness, parasthesias, and paralysis. However, a lack of one or more of these findings does not exclude ischemia. Pain alone may be the earliest symptom. High clinical suspicion is paramount to early intervention to save a limb. Complete arterial obstruction results in visible skin changes, with initial pallor that may be followed by blotchy, mottled areas of cyanosis and associated petechiae and blisters. Severe, steady pain in the involved extremity associated with decreased skin temperature is expected. Hypoesthesia or hyperesthesia due to ischemic neuropathy is typically an early finding, as is muscle weakness. An absent pulse distal is only so helpful. It may be an abrupt new sign of an occlusive clot or a long-standing finding of chronic vascular disease. As ischemic injury progresses, anesthesia and paralysis become evident and foreshadow impending gangrene. Preservation of light touch on skin testing is a good guide to tissue viability. Necrosis of skin and fat is a late finding.
Despite the generally held belief that limb salvage is possible with reperfusion within 4 to 6 h, tissue loss can occur with significantly shorter occlusion times. As important, mild to severe limb dysfunction is possible even with an injury involving only brief anoxia, with potential for lasting disability. The poor predictability of functional outcome after ischemic injury underscores the need to attain rapid reperfusion and not rely on a probable safe time interval until resolution of occlusion. Disability and tissue loss are inevitable after 6 h of occlusive anoxic injury.
Microemboli present clinically with pain and cyanosis in the involved digit, petechiae, and local muscle pain and tenderness at the site of infarction. Several different small areas can be affected with a shower of microemboli originating from a large or unstable source. Though mottling and decreased function may occur, pulses are preserved.
Chronic peripheral arterial insufficiency is characterized by intermittent claudication, which may progress to intermittent ischemic pain at rest. Femoral and popliteal disease often causes reproducible calf pain with activity that is relieved with rest. Pain at rest typically localizes to the foot and is aggravated with leg elevation, improves with standing, and is poorly controlled with analgesics.11 Shiny, hyperpigmented skin with hair loss and ulceration, thickened nails, muscle atrophy, vascular bruits, and poor pulses is a hallmark of chronic vascular disease. Complete arterial occlusion from thrombosis of a limb in these patients may present subacutely owing to a well-developed collateral circulation.
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