Acute arterial ischemia

Background

• Sudden decrease in perfusion that may result in irreversible limb loss.
• Etology may be thrombotic or embolic
  • Thrombosis occurs in vessels with existing atherosclerosis (generally have formed collateral circulation)
  • Embolism occurs in vessels usually free of atherosclerosis - generally do not have existing collateral circulation → results in higher level of limb ischemia than thombosis.

Clinical Features

6 Ps

• Paraesthesia - With weakness are early findings and preservation of light touch is good guide to viability
• Paralysis
• Pain - claudication or pain with leg elevation
• Pallor
• Pulselessness - helpful only if accompanies by skin changes
• Poikilothermia

Differential Diagnosis

• Peripheral artery disease
• Vascular injury

Foot diagnoses

Acute

• Foot and toe fractures
• Subtalar dislocation
• Metatarsophalangeal sprain (turf toe)
• Acute arterial ischemia
• Calcaneal bursitis

Subacute/Chronic

• Diabetic foot infection
• Peripheral artery disease
• Plantar fasciitis
• Trench foot
• Ingrown toenail
• Tinea pedis

Evaluation

Ankle-brachial index (ABI)

• How to measure:
  1. Position patient supine
  2. Measure SBP from both brachial arteries using cuff and handheld Doppler over the AC fossa
  3. Measure SBP from both DP and PT arteries using cuff placed just proximal to the malleoli with Doppler over artery (5-8% of normal patients have absent DP pulse)
  4. Calculate ABI on each leg by taking the highest ankle SBP (between DP and PT) on that leg divided by the highest brachial SBP and record to 2 decimal places

ABI	Meaning
<0.40	Severe occlusion
0.40–0.69	Moderate occlusion
0.70–0.90	Mild occlusion
0.91–1.30	Normal
>1.30	Poorly compressible/calcified vessels

Imaging

• Formal angiogram considered gold standard
• CTA
• US

Thrombosis vs Embolus

Key features	Thrombosis	Embolus
Source	Usually unknown	Heart (A-fib most common)
History	PAD, claudication	Less likely to have PAD and claudication
Physical exam	Absent pulse. Consistent with PAD: hair loss, thickened nails etc	Absent pulse. Usually no evidence of PAD
Degree of arthersclerosis	Diffuse	Minimal
Collaterals	Well-developed	Few

Management

• Unfractionated heparin
  • 80 units/kg bolus → 18units/kg/hr gtt
• ASA
• Dependent positioning
• Pain control
• Vascular surgery consultation (clot retrieval, balloon angioplasty, intraarterial tPA, stenting, bypass)
  • Management of embolism = embolectomy (limb salvage decreases after 4-6 hours)
  • Management of thrombus = intra-arterial thrombolysis (if non-limb threatening), thrombectomy (if limb-threatening ischmia)

Disposition

• Admit

See Also

• Peripheral artery disease
• Vascular injury

References

Authors

Ross Donaldson