• Clinical science

Acute limb ischemia

Abstract

Acute limb ischemia is a vascular emergency with a critically reduced arterial blood supply of one or more extremities. Most cases are caused by arterial embolisms originating in the heart, especially the left atrium. Arterial thrombosis is responsible for the majority of remaining cases. Regardless of the severity, ALI almost always presents with limb pain. Further symptoms include, e.g., pallor, coldness, and no pulse in the affected extremity. Diagnostics should always include a physical examination and arterial and venous doppler studies. Further imaging studies, such as digital subtraction angiography, should only be performed if this delay of treatment does not threaten the extremity. Clinical findings in combination with doppler studies are then used to categorize the limb as either viable, threatened, or nonviable. Management of viable and threatened limb ischemia begins with intravenous heparin followed by revascularization. Irreversible limb ischemia requires immediate amputation of the limb. Postoperatively and depending on the etiology, longterm anticoagulation and further diagnostic studies might be necessary (e.g., echocardiography in suspected left atrial thrombus formation).

Etiology

Pathophysiology

  • Ischemic tolerance time, after which irreversible tissue damage begins to take place
    • Skin: 12 h
    • Musculature: 6–8 h
    • Neural tissue: 2–4 h

Clinical features

  • The 6 Ps (according to Pratt)
    • Pain
    • Pallor
    • Pulselessness
    • Paralysis
    • Paresthesia
    • Poikilothermia
  • Embolism: acute onset; medical history of heart disease (e.g., atrial fibrillation)
  • Arterial thrombosis: subacute onset; medical history of arterial occlusion
  • Exam shows decreased peripheral sensitivity, pulse, and motor skills

References:[1]

Subtypes and variants

(Acute) Leriche syndrome

Occlusion at the bifurcation of the aorta usually presenting with:

Hair tourniquet syndrome

  • Definition: a medical condition wherein a hair or other thread gets wound around an appendage tightly, so as to put it at risk of ischemic damage.
  • Epidemiology: usually affects infants
  • Pathophysiology: hairs or thread inside socks or under bed sheets become spontaneously tied round a toe and tighten with the child's movement → the 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 fibre may be visible.
  • Treatment prompt removal of the constricting hair or fiber, either by means of a hair dissolving product or a scalpel.

Stages

The severity of ALI is assessed through physical examination and doppler studies and can range from viable to nonviable limb (irreversible ischemia).

Sensory loss Muscle weakness Pain Hand-held Doppler signal
Arterial Venous
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

References:[1]

Diagnostics

  • Best initial test: arterial and venous doppler
  • Confirmatory test: angiography (DSA, CTA, MRA)
    • Digital subtraction angiography (DSA) is the imaging modality of choice.
    • Should only be performed if delaying treatment for further imaging does not threaten the extremity
  • Depending on the suspected etiology, other tests may be indicated (e.g., echocardiography if an arterial embolism is suspected).

References:[1]

Treatment

  • 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
        1. Urgent angiography to localize the site of the occlusion
        2. Revascularization procedure (open or catheter-directed) within 6–24 hours
      • Threatened limb: emergent revascularization procedure within 6 hours
        • First-line: catheter-directed thrombolysis and/or percutaneous mechanical thromboembolectomy (e.g., balloon catheter embolectomy)
        • Second-line: open thromboembolectomy
      • Non-viable limb: limb amputation
  • Acute limb ischemia due to compartment syndrome: fasciotomy (see compartment syndrome)
  • Acute limb ischemia due to a dissecting aneurysm: stenting and/or surgical repair

Complications

References:[1]

We list the most important complications. The selection is not exhaustive.