Acute arterial ischemia

Background

• Sudden decrease in perfusion that may result in irreversible limb loss.

Etiology

• Thrombotic vs Embolic
  • Thrombosis occurs in vessels with existing atherosclerosis that have already formed existing collaterals.
  • Embolism occurs in vessels usually free of atherosclerosis, therefore without existing collaterals. This results in higher level of limb ischemia.

Clinical Features

6 Ps

• Pain - Claudication or pain with leg elevation; typically earliest sign
• Paraesthesia - May be associated with weakness; preservation of light touch is good guide to viability
• Pallor
• Paralysis
• Pulselessness - May be accompanied by skin changes; late finding
• Poikilothermia - Limb is cool to touch when compared to other side; late finding

Differential Diagnosis

• Peripheral artery disease
• Vascular injury

Foot diagnoses

Acute

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

Subacute/Chronic

• Diabetic foot infection
• Peripheral artery disease
• Plantar fasciitis
• Trench foot
• Ingrown toenail
• Paronychia
• Tinea pedis
• Morton's neuroma
• Diabetic neuropathy

Evaluation

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 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

• 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

1. Unfractionated heparin
   • 80 units/kg bolus; then infuse 18units/kg/hr
2. ASA
3. Dependent positioning
4. Pain control
5. Fluid resuscitation and treatment of heart failure as needed to improve limb perfusion
6. 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:
     • Non-limb threatening: intra-arterial thrombolytic
     • Severe limb-threatening ischemia: thrombectomy plus bypass grafting

Disposition

• Acute limb ischemia requires inpatient management

See Also

• Peripheral artery disease
• Vascular injury