Acute Limb Ischemia (ALI)

Defined: sudden decrease in limb perfusion with a threat to limb viability
- ALI is a sequela of PAD (Peripheral Artery Disease)
15% and 30% 30-day mortality and amputation rate

Etiology:
Earlier (hours): emboli, trauma, peripheral aneurysm
Later (days): native thrombosis or reconstruction occlusion

Hx

• pain and limb function
• intensity, severity over time, onset, duration
• motor/sensory changes

Past Hx

• leg pain (Hx of claudication)
• interventions for poor circulation
• heart disease (Af) or aneurysms (possible embolic sources)

Concurrents

• Smoking, HTN, DM, Lipids
• Family Hx: CAD, stroke, Blood clots, amputations

PE

• Pain
• Pulselessness: suggestive of ALI, ABI (ankle brachial index) should confirm
  absent Doppler flow signal in feet arteries is indicative of ALI
  
• Pallor: change in color and temperature
  
• Paresthesia: half of patients have numbness
  
• Paralysis: poor prognosis

Severe if = may need urgent revascularization

1. rest pain
2. sensory loss
3. muscle weakness

Categories, Description/Prognosis, Findings (sensory/weakness)
I. Viable: not immediately threatened, None/none
IIa. Marginally threatened: salvageable if promptly treated, minimal on toes or none/none
IIb. immediately threatened, salvageable if immediately revascularized, more than toes or rest pain/mild, moderate

III. Irreversible: major tissue loss or permanent nerve damage inevitable, profound or anesthetic/ profound or paralysis (rigor)

DDx
A. ALI mimics
1. systemic shock (esp if associated with chronic occlusive disease)
2. phlegmasia cerulea dolens
3. acute compressive neuropathy

B. DDx for ALI (other than acute PAD)
1. arterial trauma
2. aortic/arterial dissection
3. arteritis with thrombosis (eg giant cel arteritis, thromboangiitis obliterans)
4. HIV arteriopathy
5. spontaneous thrombosis associated with hypercoagulable
6. popliteal advential cyst with thrombosis
7. popliteal entrapment with thrombosis
8. compartment syndrom

C. Acute PAD
1. Thrombosis of an atherosclerotic stenosed artery
2. Thrombosis of an arterial bypass graft
3. Embolism from heart, plaque or critical stenosis upstream (including cholesterol or atherothrombotic emboli secondary to endovascular procedure)
4. Thrombosed aneurysm with or without embolization

Labs
ECG, FBC, renal panel, APTT/PT, CK

suspected hypercoagulable state: anticardiolipin antibodies, high homocysteine, antiboty to platelet factor IV

Imaging
1. Arteriography
2. CT angiography
3. MR angiography

Tx
1. Unfractionated heparin unless if patient has antibody to heparin
2. Catheter-directed thrombolytic (CDT): severity allows time (category I, IIa)
3. Percutaneous aspiration thrombectomy (PAT), PMT (mechanical)
- alternative non-surgical treatment
4. Surgery
- especially for trauma
5. Amputation
- 30% of ALI = needs amputation
- 15% of those thought salvageable, requies amputation

NB.
Reperfusion Injury: Compartment Syndrome
- immediate post-procedural issues
- newly reperfused leg leads to increase vascular permeability = local edema and compartment hypertension

KEYPOINTS

• Doppler confirms ALI
• Refer all suspected ALI to vascular specialist
• All ALI should receive anticoagulation unless absolutely contraindicated
• Fasciotomy for compartment syndrome
• Despite treatment, 1 in 4 = amputation
  

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tasc-2-pad.org (pdf)