Acute lower limb ischemia

An acute limb ischemia is an acute tissue distress induced by a sudden and critical decrease in blood supply of oxygen. It can result from arterial occlusion or, more rarely, from extensive deep vein thrombosis (phlegmasia cerulea dolens).

This is a medical-surgical emergency. The mortality rate is approximately 25% (increases with age).

Etiologies

• EMBOLI (40 to 50%) : the most affected territories are the femoral bifurcations > popliteal > aortoiliac
  • Cardiac origin (80 to 90%)
    • 70% : due to atrial fibrillation, often in the context of ischemic heart disease
    • 20% : following myocardial infarction (often within 15 days)
    • Cardiac aneurysm, bacterial endocarditis, cardiac tumor, thrombosis of mechanical valves, cardioversion,…
  • Extra-cardiac origin (5 to 10%)
    • Aneurysms (abdominal aorta, iliac, popliteal, subclavian, axillary), ulcerated or vegetative atherosclerosis, thrombosed prosthesis, paradoxical embolism, septic embolism, complication of arterial catheterization, aortic tumor (exceptional),…
  • Unidentified origin (5 to 10%)
• ARTERIAL THROMBOSES (50 to 60%)
  • Occlusion of atherosclerotic arteries +++
  • Thromboses of aneurysms ++ (popliteal > femoral > iliac > aortic)
  • Thrombosis of bypass grafts
  • Iatrogenic (ergotism, long-term estrogen-progestin,… + heparin allergy)
  • Extrinsic compression (trapped popliteal artery, popliteal cyst, compartment syndrome, tumors,…)
  • Arteritis (Takayasu, PAN, Buerger, scleroderma,…)
  • States of hypercoagulability (myeloproliferative syndrome, neoplasia, SLE, deficiencies in coagulation factors)
• OTHER CASES :
  • Vascular trauma
  • Aortic dissection (compression of the arterial orifice by the false channel)

Clinical Diagnosis

Establish the diagnosis, determine the level of occlusion, assess the degree of ischemia.

The diagnosis is primarily clinical : “ the 5 P’s ”:

• Pain (intense pain with a sudden onset localized to the muscle group downstream of the occlusion)
• Paresthesias (involvement of the vasa nervorum)
• Paralysis
• Pallor (pale and cold limb)
• No distal pulses

Neurological signs are inconsistent, may appear later, and reflect the severity of the occlusion. Paresthesias, reduced sensitivity to light touch, and proprioceptive impairment are the first symptoms. It is also necessary to check for paresis and a decrease or abolition of deep tendon reflexes. Abolition of pain sensation and complete paralysis are late signs.

Additionally, venous stasis (livor) may appear, which can mislead the clinician (DD: DVT).

Clinical examination :

• Complete vascular examination (do not forget the pulsatility of the external iliacs, assess capillary pulse by elevating both feet… beware of transmitted pulsations! Pulses upstream of the occlusion may be increased; note the level where the limb becomes pale and cold) to determine the level of occlusion, including the pulsatility of the axillary arteries and blood pressure in both arms (for potential axillo-femoral bypass)
• Assess the possibility of mesenteric ischemia during abdominal examination and history taking
• Neurological examination : sensitivity, motor function, and deep tendon reflexes !
• Appearance of the skin

Pre-therapeutic complementary examinations

No examination can delay the implementation of treatment deemed urgent (class 2b/3)… especially for angiography, which may be difficult to obtain… or even for echo-Doppler.

Systematic

• Biology
  • Complete blood count, blood glucose, electrolytes, renal function, myoglobin, CK, ABO and Rh group, search for irregular agglutinins, coagulation function (including INR and fibrinogen)
• Electrocardiogram
• Echo-Doppler of the lower limbs +- extended to the rest of the vascular tree
  • Degree of ischemia, site of occlusion, search for a source of thrombosis (aneurysm or trap) or emboli (AAA,…)

Non-systematic

• Conventional angiography
  • In case of urgent revascularization, angiography may be performed intraoperatively. In case of thrombosis on a bypass graft, one can rely on recent imaging.
  • Helps in revascularization, etiological diagnosis, visualization of potential latent emboli
  • Of little interest in front of a typical history of embolism on healthy arteries with absent femoral pulses (likely embolism from the aortic bifurcation due to heart disease)

Rutherford Classification

Class 1 : Viable limb without therapeutic intervention

Class 2 : Revascularization necessary for limb viability

• 2a : Revascularization that can be deferred (subacute ischemia)
• 2b : Revascularization that must be immediate !

Class 3 : Exceeded ischemias (condemned limb)

Etiological Diagnosis

It is necessary to try as much as possible to make a preliminary etiological orientation (embolic or thrombotic?) based on clinical assessment to guide complementary examinations and treatment. The rest of the approach should be undertaken after treatment.

Embolic Origin

The most frequent origin (90%) is cardiac, looking for a recidivist atrial fibrillation, recent myocardial infarction, recent massive PE, and patent foramen ovale,… with ECG + Echocardiography

10% of emboli are not of cardiac origin; look for an abdominal/popiteal aneurysm, iliac/superficial femoral artery stenosis in the absence of cardiac evidence : Echo of abdominal aorta/femoro-iliac.

Always search (clinical and history) for another ischemic site : mesenteric ischemia and stroke.

Embolic arterial thromboses generally fall into class 2a (deferred intervention).

Arterial Thromboses due to Arteritis

Look for known PAD in the history, any notion of intermittent claudication to perform a PAD assessment (ankle-brachial index,…)

Generally fall into classes 1 or 2a (since collateral arterial circulation has often already developed).

Thrombosis of a Bypass

Suggested by the medical history. Their frequency is increasing. Their severity is very variable: 2a/ 2b/ 3

Thrombosis on Popliteal Aneurysm

Based on clinical findings and an ultrasound of the popliteal fossa. Always serious: class 2b/ 3

Post-Traumatic Thrombosis

Clinical findings and medical history are generally conclusive. Mainly concerns: superficial femoral artery, popliteal artery, (rarely the leg arteries). Class 2b/3

Therapeutic Management - Treatments - Medical-Surgical Emergency Until Proven Otherwise

Treatment should begin within 6 hours (limit regarding the onset of irreversible muscle and nerve damage). Transfer to vascular surgery as soon as possible. Treatment plan to be determined according to clinical findings, possibly imaging, and the experience of the surgeons.

Fogarty catheter embolectomy remains the standard treatment. Surgical bypass (venous or artificial) is performed in cases of pathological arterial terrain or as a second option. Amputation is reserved for unfavorable evolutions or performed immediately in cases of exceeded ischemia or life-threatening situations. The role of intra-arterial fibrinolysis as an alternative to surgery is debated. Conclusions regarding morbidity and mortality from comparative studies are contradictory. It should be noted that, performed by an experienced radiologist, it is undeniably beneficial in cases of fresh thromboses of bypasses, and the rate of secondary strokes is 2-3%.

Immediate Medical Treatment

To be done systematically as soon as the diagnosis is made:

• Anticoagulation
  • Heparin (unfractionated!) at therapeutic doses: bolus of 80 IU/kg (~5000 UI) then 18 IU/kg/h
  • Check APTT 6 hours after the start of treatment to adjust the rate for an APTT between 65 and 90 seconds
• Aspirin 100mg/day, (statins)
• Vasodilators (++ if arteritic)
• Morphine
• Correction of electrolyte disturbances and metabolic acidosis (++ if significant disturbances and clinical state of (pre-) shock)
• Other symptomatic measures

Surgical Treatment to Consider Based on Class

Class 3

MAJOR AMPUTATION usually imposes itself (exceeded ischemia, particularly in cases threatening vital prognosis). In some cases (persistence of a distal arterial axis, rapid management, absence of renal insufficiency, no immediate life threat) a surgical revascularization may be attempted with aponeurotomies and limb washing.

Class 2b

• If necessary, a peroperative angiography will be performed
• Thrombosis by emboli on healthy arteries: staged embolectomies
• Same on arteritic terrain (the most frequent): surgical bypass (or first attempt embolectomy)
• Thrombosis of a bypass/ popliteal aneurysm/ due to trauma: immediate surgical bypass

Class 2a

• Preoperative angiography
• Thrombosis by embolism: embolectomy (or first attempt fibrinolysis)
• Thrombosis on arteritis: surgical bypass (or first attempt embolectomy)
• On thromboembolic disease: surgical bypass (or first attempt embolectomy)
• Thrombosis on bypass: surgical bypass

Class 1

• Discuss the necessity of angiography
• Optimize heparin treatment
• In case of an embolus on a healthy artery, embolectomy may be considered

Complications

Necroses - Exceeded Ischemia

Nerves and muscles resist ~6 hours of severe ischemia, the skin 24 hours

Hyperkalemia and Arrhythmias

Hyperkalemia due to cellular lysis at risk of cardiac disturbances.

Acute Renal Failure

To be associated with ARF during rhabdomyolyses… due to the release of myoglobin (acute tubular necrosis)?

Pulmonary and Cerebral Disturbances

Due to the release of various factors: platelet aggregates, procoagulant factors, inflammatory cytokines,…

Other Ischemic Sites

They are always to be sought, particularly in cases of thromboembolism. Significant frequency of mesenteric ischemia and associated strokes.

Bibliography

EMC, traité de chirurgie vasculaire, Elsevier, 2018

Mitchell ME, Clinical features and diagnosis of acute arterial occlusion in the lower extremity ischemia, UpToDate, 2024