Acute arterial ischemia

(Redirected from Acute limb ischemia)

Background

Major arteries of the body.
  • Sudden decrease in perfusion that may result in irreversible limb loss
    • Amputation occurs in 10%-15% of patients during hospitalization[1]
  • Etiology may be thrombotic (80%) or embolic (20%)[2]
    • 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 thrombosis

Clinical Features

Acute embolism to the right femoral artery resulting in ischemia.

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

Blue Digit

Foot diagnoses

Acute

Subacute/Chronic

Evaluation

Ankle-brachial index (ABI)

Ankle-Brachial Index performance.

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

Acute occlusion of the axillary artery resulting in an ischemic limb as seen on CT angiography.
  • Formal angiogram considered gold standard
  • CTA as a diagnostic is near the level of formal angiography (96% sensitive, 95% specific)[3]
  • US is sensitive for proximal extremity occlusions, but sensitivity markedly falls off distally and is operator dependent

Laboratory Evaluation

  • Not useful for diagnosis, but essential for monitoring co-existing conditions and response to anticoagulant therapy. Should include:
    • CBC
    • BMP
    • PT/PTT
    • Creatine kinase

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

Rutherford Classification[4]

Category Description/Prognosis Sensory Loss Muscle Weakness Arterial Doppler Venous Doppler
Viable (I) Not immediately threatened None None Audible Audible
Marginally threatened (IIa) Salvageable if promptly threatened Minimal (toes) or none None Often inaudible Audible
Immediately threatened (IIb) Salvageable with immediate revascularization Extends beyond toes; pain at rest Mild to moderate Usually inaudible Audible
Irreversible damage (III) Major tissue loss or permanent nerve damage inevitable Profound, anesthetic Profound, paralysis or rigor Inaudible Inaudible

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)
  • Interventional radiology if delay in vascular surgery intervention or if unavailable

Disposition

Admission

  • Patients with an ABI of <0.5 warrant admission after immediate consultation with vascular surgery

Discharge

  • Patients with stable ABI measurements, resolved pain, and chronic occlusive disease can be discharged with vascular surgical follow-up.

See Also

External Links

References

  1. ↑ Norgren L, Hiatt WR, Dormandy JA, et al. Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II). J Vasc Surg. 2007;45 Suppl S:S5-S67. doi:10.1016/j.jvs.2006.12.037
  2. ↑ Mitchell ME, Carpenter JP. Overview of acute arterial occlusion of the extremities (acute limb ischemia). In: Post TW, ed. UpToDate. Waltham, MA: UpToDate. https://www.uptodate.com/contents/overview-of-acute-arterial-occlusion-of-the-extremities-acute-limb-ischemia?source=search_result&search=Classification%20of%20acute%20extremity%20ischemia&selectedTitle=1~90#H506059593.Last updated: May 30, 2016. Accessed: December 12, 2016.
  3. ↑ Jens S, Koelemay MJ, Reekers JA, Bipat S. Diagnostic performance of computed tomography angiography and contrast-enhanced magnetic resonance angiography in patients with critical limb ischaemia and intermittent claudication: systematic review and meta-analysis. Eur Radiol. 2013;23(11):3104-3114. doi:10.1007/s00330-013-2933-8
  4. ↑ Rutherford RB. Clinical staging of acute limb ischemia as the basis for choice of revascularization method: when and how to intervene. Semin Vasc Surg 2009;22:5-9.
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