Acute limb ischemia (ALI) is a vascular emergency in which the arterial blood supply to one or more extremities is critically reduced. Arterial thrombosis and cardiac emboli are responsible for the majority of cases. The typical signs and symptoms of ALI include pain, pallor, pulselessness, poikilothermia, paralysis, and paresthesia of the limb distal to the site of vascular occlusion (the 6 Ps). Diagnosis relies on examination and arterial Doppler studies. Clinical findings in combination with Doppler studies are then used to categorize the limb as viable, threatened, or nonviable. Further imaging studies, e.g., digital subtraction angiography, should only be performed if they do not result in treatment delays. Management of viable and threatened limb ischemia begins with intravenous heparin followed by revascularization. Irreversible limb ischemia will inevitably progress to gangrene and requires amputation of the nonviable parts of the limb. Whether long-term anticoagulation and/or further diagnostic studies are required depends on the suspected etiology (e.g., echocardiography in suspected left atrial thrombus formation).
Arterial occlusion 
- Trauma leading to transsection, dissection, or thrombosis of a vessel
- Aortic dissection
- Compartment syndrome
- Arterial vasoconstriction
- Venous occlusion ( )
- The lower limb is affected in > 80% of cases.
- Arterial thrombosis: subacute onset; history of claudication pain
- Embolism: acute onset; history of heart disease (e.g., )
- The 6 Ps distal to the site of occlusion
Subtypes and variants
- Pain in both legs and the buttocks
- Bilaterally absent femoral, popliteal, and ankle pulses
- Erectile dysfunction
Hair tourniquet syndrome
- Definition: : a condition in which a hair or thread becomes wound around an appendage tightly, putting the appendage at risk of ischemic damage
- Epidemiology: usually affects infants
- Pathophysiology: hairs or threads inside socks or under bed sheets can become spontaneously tied round a toe and tighten with the child's movement → venous and lymphatic return is impaired → further obstruction may cause arterial occlusion and ischemic injury
- Clinical features: painful, swollen, reddened appendage with a deep groove proximal to it, in which the constricting fiber may be visible
- Treatment: prompt removal of the constricting hair or fiber, either by means of a hair-dissolving product or a scalpel
- Definition: peripheral ischemia due to prolonged treatment with vasopressors (e.g., norepinephrine)
- Pathophysiology: prolonged alpha receptor agonism → vasospasm of distal arterioles and their branches → ischemia and consequent necrosis of most distal extremities
- Clinical features: symmetrical cyanosis, coldness, and necrosis of fingers and/or toes
|Sensory loss||Muscle weakness||Pain||Hand-held Doppler signal|
|Viable||None||None||Mild to moderate||Audible flow||Audible flow|
|Threatened||Minimal||Mild to moderate||Severe||No flow||Audible flow|
|Nonviable||Anesthetic limb||Paralysis||None||No flow||No flow|
- Tests to confirm the diagnosis and identify the site(s) of occlusion
Best initial test: arterial and venous Doppler
- Diminished or absent Doppler flow signal distal to site of occlusion.
- Confirmatory test: angiography (DSA, CTA, MRA)
- Best initial test: arterial and venous Doppler
- Depending on the suspected etiology, other tests may be indicated (e.g., echocardiography if an arterial embolism is suspected).
Acute limb ischemia due to thromboembolism
- Systemic anticoagulation with an IV heparin bolus followed by continuous infusion unless a contraindication is present
- Further management depends on the severity of acute limb ischemia.
- Viable, non-threatened limb
- Threatened limb: emergent revascularization procedure within 6 hours
- Non-viable limb: limb amputation
- Acute limb ischemia due to compartment syndrome: fasciotomy (see )
- Acute limb ischemia due to a dissecting aneurysm: stenting and/or surgical repair
- Permanent nerve damage: sensory loss, muscle weakness, paralysis
- Loss of limb due to irreversible ischemia
- Reperfusion injury (postischemic syndrome)
We list the most important complications. The selection is not exhaustive.