Acute Limb Ischaemia

Notes

Critical Care Medicine | Vascular Surgery | Vascular Surgical Emergencies

Overview

Acute limb ischaemia refers to any sudden decrease in limb perfusion that causes a potential threat to viability. It is associated with pain, motor and sensory loss, and cold sensation. It affects one in about 6000 of the population¹ and is more common in the lower limb, with less than 17% of cases affecting the upper limb⁴. If left untreated, it can lead to limb loss or even death³.

Definition

Acute limb ischaemia is defined by a rapid drop in arterial blood flow resulting in cessation of nutrient and oxygen delivery to the tissues.
Compartment syndrome is a complication that occurs when there is an increase in pressure in a closed muscle compartment leading to compression of blood vessels and nerves, causing swelling, tightness and pain.

Aetiology and Risk Factors

Acute thrombosis in a vessel with preexisting atherosclerosis (60% of cases):

May arise from plaque rupture, hypovolemia, increased blood coagulability, or myocardial infarction⁵

Emboli (30% of cases)

More than 70% of emboli are attributed to atrial fibrillation⁵

Less common

Aortic dissection
Trauma
Iatrogenic injury
Peripheral aneurysm (particularly popliteal)
Intra-arterial drug use

Think

Sudden onset limb ischaemia in a previously normal limb suggests embolism (often cardiac source, e.g. AF) where as gradual onset, collaterals present → more likely thrombosis on pre-existing PAD.

Virchow’s triad: hypercoagulability, blood flow stasis, endothelial injury – leads to increased risk of thrombosis.

Side note

Atrial fibrillation is an atrial arrhythmia that causes impaired contraction of atria leading to blood stasis in the atrium. A clot can form and travel to an artery in the limbs, obstructing blood flow and causing ischaemia.

Risk Factors

Metabolic: ischaemic heart disease, CKD, hypertension, hyperlipidaemia, diabetes
Active malignancy or other comorbidities promoting thrombosis
Atrial fibrillation
Smoking: current or previous
Elderly male
Previous arterial intervention

Pathophysiology

Arterial occlusion causes sudden cessation in blood flow and nutrient and oxygen delivery to tissues. This leads to the tissue relying on anaerobic instead of aerobic metabolism. Anaerobic metabolism produces lactate, which increases the acidity in affected tissue, causing muscle injury. This eventually leads to depletion of ATP and leakage of free calcium, which causes skeletal muscle fiber necrosis.⁴

Virchow’s triad – set of 3 factors that contribute to thrombosis, presence of any of the elements increases the risk of acute limb ischaemia:

Hypercoagulability
- Factor V Leiden mutation
- Antithrombin deficiency
- Protein S deficiency
- Protein C deficiency
- Malignancy
- Oral contraceptive pill
Blood flow stasis
- Immobility
- Obesity
- Pregnancy
Endothelial injury
- Smoking
- Hypertension
- Atherosclerosis

Classification

Divided into 3 classes based on Rutherford criteria:

Clinical Manifestations

The most common symptoms are the 6 Ps:

Pain
Pallor
Pulselessness
Perishingly cold
Paraesthesia
Paralysis

Clinical examination

General inspection: findings change as damage to tissue becomes more prominent, from least to most severe:

‘Marble’ white
Blanching light blue or purple mottling
Non blanching mottling darker in colour
Blistering and liquefication

Pain on squeezing muscle indicates infarction and irreversible ischaemia

Arterial pulse can be weak or absent

Acute limb ischaemia of right leg on general inspection

Diagnosis

Chronic limb ischaemia
Compartment syndrome
Sepsis (eg. diabetic foot, septic arthritis)
DVT
Infection (eg. cellulitis, infected venous ulcer, bites)
Necrotising fasciitis
Myocardial infarction (referred to upper limb pain)
Central or peripheral neuropathy (eg. stroke, Guillain-Barre)

Think

Acute limb ischaemia can have a vague presentation, such as mild pain, making the list of potential diagnosis very broad.

Diagnosis

Investigations are performed only if they do not delay urgent vascularisation.

Bedside:

ECG – to evaluate for arrhythmia (eg. atrial fibrillation)

Bloods:

Routine bloods
Lactate: assess ischaemia
Creatine kinase – to assess extent of muscle damage

Imaging:

Doppler US – elevated peak systolic velocities suggest vascular stenosis
MRI/CT angiography – gold standard imaging to detail site and extent of occlusion

Remember

Don’t delay revascularisation for imaging if the limb is immediately threatened.

Creatine kinase (CK) is an enzyme found in the heart, brain and skeletal muscles. It helps produce energy and is released when the tissue is damaged. Higher levels of CK in the blood indicate a higher degree of injury.

Treatment

Start with an A-E assessment to determine if patient is stable or unstable

Resuscitate if necessary:

Administer 100% O2
Get IV access and consider up to 1L of crystalloid fluid
Give opiate analgesia, usually morphine
Request appropriate tests – blood, ECG and imaging
Keep patient Nil by Mouth in case surgery is needed

1. Give unfractionated heparin to all patients if there are no contraindications (eg. aortic dissection, multiple traumas, head injury) (1)

2. Early vascular consult and confirmatory imaging

Digital Subtraction Angiography (DSA)
Computed Tomography Angiography (CTA)
Magnetic Resonance Angiography (MRA)

Unfractionated heparin is an anticoagulant that is commonly used in patients with venous thromboembolism and cardiovascular disease. Mechanism of action: binds to antithrombin III enhancing its activity, which in turn deactivates factors IIa (thrombin) and Xa. Side effects: the most common is bleeding. Unfractionated heparin can be reversed with protamine sulfate.

3. Perform a limb vitality assessment using examination and urgent Doppler (^1,4):

Examination and doppler	Suggests	Definitive treatment
Normal examination Doppler – arterial and venous flow both audible	Viable	Conservative management, usually with anticoagulation
Sensory loss in toes, intact motor Doppler – arterial flow may be absent	Marginally threatened	Salvageable with revascularisation
Sensory + motor loss Doppler – absent arterial flow	Immediately threatened	Requires urgent revascularisation Fasciotomy (if compartment syndrome suspected)
Fixed mottling, hard muscles Doppler – absent arterial and venous flow	Irreversible ischaemia	Amputation likely

Remember

Consider fasciotomy if delayed revascularisation → compartment syndrome risk.

Diagram showing approach to management²

Fasciotomy is a surgical procedure where the fascia (connective tissue covering various organs, including muscles) is cut open to relieve pressure.

Thrombolysis is the use of medication to break down clots. It is used in ischaemia, pulmonary embolism and myocardial infarction. Common medications are urokinase and drugs ending with the suffix -plase (eg. alteplase). Mechanism of action: convert plasminogen to plasmin, which initiates breakdown of fibrin.

Angioplasty is a procedure used to dilate narrow arteries. A catheter is placed in the vessel and a balloon is inflated at the point of narrowing causing the vessel lumen to dilate. A stent is often left in place to prevent recurrent narrowing.

Embolectomy is a surgical procedure used to remove an embolus (blood clot) from an artery. A balloon catheter is inserted inside the artery and the balloon is inflated distal to the embolus, the balloon is then retrieved out of the artery together with the embolus.

Complications and Prognosis

Complications

Limb loss or death
Reperfusion injury
Compartment syndrome
Neurological injury
Arterial ulcers

Reperfusion injury can occur when blood supply is restored in tissue that has been deprived of oxygen, which causes release of free radicals, oxidative stress and inflammation. This can lead to swelling and cell death.

Prognosis

The mortality and amputation rates depend on the type of treatment received, presence of comorbidities and stage of ischaemia. ⁷

The in-hospital mortality ranges between 10-20%.⁵

References

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Lacey HMMAM. Vascular surgery. In: Lacey HMMAM, editor. Crash Course Surgery2025. p. 171-205. https://www.clinicalkey.com/student/content/book/3-s2.0-B9780443115714000065
Coșarcă MC, Lazăr NA, Șincaru SV, Bandici BC, Argatu EC, Carașca C, et al. Treatment Strategies and Prognostic Outcomes in Acute Limb ischaemia: A Systematic Review and Meta-Analysis Comparing Thrombolytic Therapy and Open Surgical Interventions. Medicina. 2025;61(5):828. https://doi.org/10.3390/medicina61050828
Arnold J, Koyfman A, Long B. High risk and low prevalence diseases: Acute limb ischaemia. The American Journal of Emergency Medicine. 2023;74:152-8. https://doi.org/10.1016/j.ajem.2023.09.052
Tambyraja AL. Vascular and endovascular surgery. In: Garden OJCBEBMBCMDDFFFFFFFFFF, Parks RWMBBBAOMDFFF, Wigmore SJBMMDFFF, editors. Principles and Practice of Surgery2023. p. 368-401. https://www.clinicalkey.com/student/content/book/3-s2.0-B9780702082511000224
Cai PL, Forsyth JM. Acute limb ischaemia. Surgery (Oxford). 2025;43(5):319-28. https://doi.org/10.1016/j.mpsur.2025.03.005
Genovese EA, Chaer RA, Taha AG, Marone LK, Avgerinos E, Makaroun MS, et al. Risk Factors for Long-Term Mortality and Amputation after Open and Endovascular Treatment of Acute Limb ischaemia. Annals of Vascular Surgery. 2016;30:82-92. https://doi.org/10.1016/j.avsg.2015.10.004