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    Acute Limb Ischemia


    Last Updated Jan 19, 2022
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    By Joseph Chong, Tracy Huynh


    • More than 200 million people globally have lower extremity peripheral artery disease.
    • Incidence of acute limb ischemia is 1.5 cases per 10,000 persons per year.
    • High rates of morbidity and mortality, requires high index of suspicion for catastrophic outcomes:
      • Despite urgent revascularization, amputation occurs in 10-15% of patients.
      • 15-20% of patients die within 1 year after presentation.
    • Definitions:
      • Acute limb ischemia: sudden disruption of limb perfusion threatening limb viability, occurring within previous 2 weeks.
      • Chronic limb ischemia: most commonly caused by PAD, gradually worsens over time, symptoms of claudication.
      • Critical limb ischemia: limb pain that occurs at rest, can result in loss of tissue such as skin ulceration or gangrene.
        • Signifies severely compromised limb perfusion, may be result of acute or chronic ischemia.

    Diagnostic Process

    • Risk Factors:
      • Thrombosis: most likely to occur at site of atherosclerosis.
      • Embolism: from heart or diseased artery.
      • Hypercoagulability.
      • Trauma.
      • History of arterial interventions.
    • History:
      • Rule out other ischemic and non-ischemic causes of limb pain:
        • Compartment syndrome, DVT.
        • Trauma, gout.
      • Focus on when symptoms started, which limb, events surrounding onset.
      • Classic 6 P’s: absence of these symptoms does not rule out ALI.
        • Pain
        • Pallor
        • Pulselessness
        • Poikilothermia: impaired regulation of body temperature
        • Paresthesia
        • Paralysis: ominous sign
      • ALI is not relieved by rest.
      • Embolic source more likely: acute onset of ischemic symptoms in a previously asymptomatic patient with no history of claudication.
      • Thrombotic source more likely: sudden worsening of symptoms in a patient with known history of claudication/peripheral vascular disease; more vague in onset.
    • Physical Exam:
      • Absence of pulses distal to occlusion but bounding pulses proximal to it.
        • Lower limb pulses: femoral, popliteal, dorsalis pedis, posterior tibial.
        • Upper limb pulses: brachial, radial, ulnar.
      • Pale or cool skin.
      • Motor and sensory exam might reveal weakness, decreased sensation.
    • Investigations:
      • CBC, electrolytes, renal function, creatine kinase, coagulation profile.
      • Imaging if appropriate: duplex ultrasound, CT angiography, MR angiography.
        • CTA usually offers highest yield, with reconstruction invaluable for planning endovascular approach.
        • Duplex ultrasound is less sensitive for detecting vascular pathology.
    • ·Diagnostic approach:
      • Evaluate pulses.
      • If pulses not palpable, determine presence of flow with Doppler.
      • If flow present, determine perfusion pressure proximal to Doppler probe using sphygmomanometric cuff (ABI).
        • ABI is ratio of sBP of foot to highest brachial pressure in either arm.
        • Normal ABI = 0.91 to 1.3
        • Critical ABI = <0.4
        • Classify ALI severity: Rutherford Classification

    Image taken from Creager et al. Acute Limb Ischemia. N Eng J Med. 2012; 366: 2198-2206.

      • Classification between stage I to IIA and IIB to III is important because mirrors. decision for an endovascular approach vs open surgical approach, respectively.


    Image taken from Creager et al. Acute Limb Ischemia. N Eng J Med. 2012; 366: 2198-2206.

    • Initial management:
      • IV unfractionated heparin: dosing decision should be made with vascular surgery.
        • Baseline recommendations: 80-150 U/kg bolus followed by infusion of 18 U/kg/hr to achieve PTT 2-2.5.
      • Aspirin 325 mg PO.
      • Keep patient in dependent position and warm the limbs.
      • Pain control.
      • Fluid resuscitation in hypovolemic patient.
    • Timing of intervention: <6 hours is optimal because patients presenting with >6 hr between symptom onset and intervention are 40x more likely to undergo amputation.
    • Endovascular:
      • Involves use of thrombolytics injected directly into thrombus over 12-24 hours, mechanical devices, or both to restore blood flow.
      • Associated with higher rates of stroke and major hemorrhage within 30 days compared to surgical revascularization.
    • Open surgical revascularization:
      • Approaches include thromboembolectomy with balloon catheter, bypass surgery.
      • Often requires subsequent operative intervention at 30 days.
      • Associated with higher mortality in the elderly population.
    • Long-term management:
      • Warfarin for patients with thrombosis of native artery.
      • DOACs may be considered in patients with embolism secondary to afib.
      • Aspirin and/or clopidogrel for patients with thrombosis superimposed on atherosclerotic plaque: reduce risk of MI, stroke.
      • Lifestyle management: smoking cessation, exercise, manage dyslipidemia.
    • Clinical endpoint: disposition depends on severity of ischemia (see Rutherford Classification), etiology (embolic vs thrombotic), timing of symptoms, urgency for revascularization.
      • All patients with ALI requiring surgical intervention should be admitted to hospital under the consultation of Vascular Surgery for immediate revascularization or amputation (if limb irreversibly damaged).


    Quality Of Evidence?


    Review articles and society recommendations, no RCTs.


    Related Information


    Related Information

    Reference List

    1. Braun R, Lin M. Acute Limb Ischemia: A Case Report and Literature Review. J Emerg Med. 2015; 49(6): 1011-1017.

    2. Creager MA, Kaufman JA, Conte MS. Acute Limb Ischemia. N Eng J Med. 2012; 366: 2198-206.

    3. Kashyap VS, Gilani R, Bena JF, Bannazadeh M, Sarac T. Endovascular therapy for acute limb ischemia. J Vasc Surg. 2011; 53(2): 340-46.

    4. McNally MM, Univers J. Acute Limb Ischemia. Surg Clin N Am. 2018; 98(5):1081-1096.

    5. Norgren L, Hiatt WR, Dormandy JA, Nehler MR, Harris KA, Fowkes FGR, on behalf of the TASC II Working Group. Inter-Society Consensus for the Management of Peripheral Arterial Disease (TASC II). J Vasc Surg. 2007; 45(1) Suppl:S5-S67.

    6. Rutherford RB, Baker JD, Ernst C, et al. Recommended standards for reports dealing with lower extremity ischemia: revised version. J Vasc Surg. 1997; 26:517-38.


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