Overview
Acute Limb Ischaemia
1. Clinical Overview
Summary
Acute limb ischaemia (ALI) is sudden reduction in limb perfusion threatening limb viability. Classic presentation is the "6 Ps": Pain, Pallor, Pulselessness, Perishing cold, Paraesthesia, Paralysis. Causes are thrombosis (in situ) or embolism (commonly cardiac from AF). Time to revascularisation determines outcome — viable limbs require urgent intervention within 6-24 hours. Treatment is anticoagulation (heparin), revascularisation (surgical or endovascular), and addressing the underlying cause.
Key Facts
- Definition: Sudden decrease in limb perfusion threatening viability
- Presentation: 6 Ps — Pain, Pallor, Pulselessness, Perishing cold, Paraesthesia, Paralysis
- Causes: Embolism (60%) — usually cardiac (AF); Thrombosis (40%) — in situ in diseased artery
- Treatment: Heparin + urgent revascularisation (embolectomy, thrombolysis, bypass)
- Time-critical: Irreversible muscle necrosis begins within 4-6 hours
- Irreversibility signs: Fixed mottling, muscle rigidity, sensory/motor loss — may require amputation
Clinical Pearls
The 6 Ps of acute limb ischaemia: Pain, Pallor, Pulselessness, Perishing cold, Paraesthesia, Paralysis
Paraesthesia and paralysis indicate impending irreversibility — urgent intervention required
Sudden onset + AF = embolic until proven otherwise
Why This Matters Clinically
ALI is a surgical emergency. Delay leads to limb loss. Early recognition, immediate anticoagulation, and rapid vascular surgery involvement are essential.
2. Epidemiology
Visual assets to be added:
- 6 Ps diagram
- Acute limb ischaemia clinical photograph
- Angiogram showing arterial occlusion
- Rutherford classification table
Epidemiology
Incidence
- 1.5 per 10,000/year
- More common in elderly (atherosclerotic disease, AF)
Demographics
- Peak age: Over 60
- Male predominance
Causes
| Type | Cause | Proportion |
|---|---|---|
| Embolism | Cardiac (AF, MI, endocarditis), aortic (aneurysm, atheroma) | 60% |
| Thrombosis | In situ thrombosis in diseased artery (PAD), graft occlusion | 40% |
| Other | Trauma, dissection, popliteal aneurysm | Rare |
Risk Factors
- Atrial fibrillation
- Peripheral arterial disease
- Recent MI
- Aortic aneurysm
- Hypercoagulable states
3. Pathophysiology
Mechanism
- Sudden arterial occlusion (embolus or thrombus)
- Tissue ischaemia → anaerobic metabolism
- Lactic acidosis, myoglobin release
- Initially reversible; becomes irreversible within hours
Time to Irreversibility
- Skeletal muscle tolerates ischaemia for 4-6 hours
- Nerve: Symptoms appear early (paraesthesia)
- After 6-8 hours: Muscle necrosis begins
- Fixed mottling, rigidity = irreversible damage
Embolism vs Thrombosis
| Feature | Embolism | Thrombosis |
|---|---|---|
| Onset | Sudden | Subacute (may have prior claudication) |
| Contralateral pulses | Present | Often absent (generalised PAD) |
| Source | Cardiac (AF), proximal aneurysm | In situ in diseased artery |
| Collaterals | Absent | May be present |
Reperfusion Injury
- Revascularisation releases K+, lactate, myoglobin
- Risk of hyperkalaemia, acidosis, myoglobinuria (AKI)
- Compartment syndrome possible
4. Clinical Presentation
The 6 Ps
| Sign | Description |
|---|---|
| Pain | Severe, sudden onset, in affected limb |
| Pallor | White/waxy skin (early); mottled (late) |
| Pulselessness | Absence of distal pulses |
| Perishing cold | Cold limb |
| Paraesthesia | Numbness, tingling (early neurological sign) |
| Paralysis | Motor loss (late sign — indicates impending irreversibility) |
Distinguishing Features
| Viable | Threatened | Irreversible |
|---|---|---|
| No sensory loss | Sensory loss | Fixed mottling |
| No motor loss | Motor weakness | Muscle rigidity |
| Capillary refill present | Prolonged capillary refill | No capillary refill |
Red Flags
| Finding | Significance |
|---|---|
| Paralysis | Limb threatened — urgent intervention |
| Fixed mottling | Likely irreversible |
| Muscle rigidity | Irreversible — amputation likely |
5. Clinical Examination
Limb Examination
- Colour: Pale early; mottled late; fixed staining = irreversible
- Temperature: Cold; marked demarcation from normal tissue
- Pulses: Absent distal pulses; check contralateral
- Capillary refill: Delayed or absent
- Sensation: Reduced (early)
- Motor function: Weakness → paralysis (late)
- Muscle: Soft vs rigid (rigid = necrosis)
Cardiovascular
- Pulse (AF)
- Auscultate heart (murmurs — endocarditis)
- Aortic aneurysm (palpate abdomen)
Contralateral Limb
- Pulses present (suggests embolism)
- Pulses absent (suggests generalised PAD, thrombosis)
Hand-Held Doppler
- Assess arterial signals (present, monophasic, absent)
- ABPI if time permits (often not in emergency)
6. Investigations
Immediate
| Test | Purpose |
|---|---|
| ECG | Atrial fibrillation (embolic source) |
| FBC, U&E, creatinine | Baseline, renal function |
| Clotting | Baseline, heparin monitoring |
| Group & Save | Pre-operative |
| Lactate | Severity of ischaemia |
| CK, myoglobin | Rhabdomyolysis |
Imaging
| Modality | Role |
|---|---|
| CT angiography | Preferred — shows site and extent of occlusion |
| Duplex ultrasound | Alternative if CT not available |
| Digital subtraction angiography (DSA) | If proceeding to endovascular intervention |
Echocardiography
- If embolic source suspected
- Look for thrombus, vegetations
Classification & Staging
Rutherford Classification
| Category | Description | Prognosis |
|---|---|---|
| I (Viable) | No sensory or motor loss | Not immediately threatened |
| IIa (Marginally threatened) | Minimal sensory loss, no motor loss | Salvageable with prompt treatment |
| IIb (Immediately threatened) | Sensory loss + mild motor loss | Salvageable with urgent revascularisation |
| III (Irreversible) | Profound sensory/motor loss, muscle rigidity, fixed mottling | Amputation required |
7. Management
Immediate
1. Analgesia:
- IV opioids (morphine)
2. Anticoagulation:
- IV unfractionated heparin bolus (5000 units) + infusion
- Prevents clot propagation
3. Supportive:
- IV fluids
- Keep limb horizontal (not elevated or dependent)
- Protect from pressure/trauma
Definitive Treatment
| Approach | Indication |
|---|---|
| Surgical embolectomy | Embolic occlusion; can be done under local/regional |
| Catheter-directed thrombolysis | Thrombosis in situ; longer treatment time (12-24h) |
| Bypass surgery | Extensive disease, failed embolectomy |
| Endovascular thrombectomy | Increasingly used |
| Amputation | Irreversible ischaemia (Category III) |
Post-Revascularisation
- Monitor for reperfusion injury (hyperkalaemia, acidosis, myoglobinuria)
- Watch for compartment syndrome (fasciotomy if needed)
- Anticoagulation (if embolic source)
- Investigate and treat underlying cause (AF, aneurysm)
Secondary Prevention
- Anticoagulation if AF (DOAC/warfarin)
- Cardiovascular risk factor modification
- Duplex surveillance if graft/stent
8. Complications
Of Ischaemia
- Limb loss (amputation)
- Rhabdomyolysis → AKI
- Compartment syndrome
- Multiple organ failure
Of Revascularisation
- Reperfusion injury (hyperkalaemia, acidosis)
- Compartment syndrome
- Bleeding
- Graft/stent thrombosis
9. Prognosis & Outcomes
Limb Salvage
- Category I/IIa: Excellent with prompt treatment
- Category IIb: Good if revascularised within hours
- Category III: Amputation required
Mortality
- 30-day mortality: 10-15%
- Higher in elderly, delayed presentation, comorbidities
Long-Term
- Recurrence risk if embolic source not addressed
- Ongoing cardiovascular risk
10. Evidence & Guidelines
Key Guidelines
- ESVS Clinical Practice Guidelines on the Management of Acute Limb Ischaemia (2020)
- NICE NG37: Peripheral Arterial Disease (2012)
Key Evidence
- Surgical embolectomy remains gold standard for embolic ALI
- Thrombolysis non-inferior for thrombotic occlusion in selected cases
11. Patient/Layperson Explanation
What is Acute Limb Ischaemia?
Acute limb ischaemia is when the blood supply to an arm or leg is suddenly blocked. Without treatment, the limb can be permanently damaged and may need to be amputated.
Symptoms
- Sudden severe pain in the leg or arm
- The limb becomes pale, cold, and numb
- Weakness or inability to move the limb
Treatment
- Blood-thinning medication (heparin)
- Surgery or a procedure to restore blood flow
- Sometimes amputation is necessary if the damage is severe
Prevention
- If you have an irregular heartbeat (AF), take your blood-thinning medication as prescribed
- Quit smoking
- Manage blood pressure and cholesterol
Resources
12. References
Primary Guidelines
- Björck M, et al. Editor's Choice – European Society for Vascular Surgery (ESVS) 2020 Clinical Practice Guidelines on the Management of Acute Limb Ischaemia. Eur J Vasc Endovasc Surg. 2020;59(2):173-218. PMID: 31899099
Key Studies
- Surgery versus Thrombolysis for Ischemia of the Lower Extremity (STILE) Trial Investigators. Results of a prospective randomized trial evaluating surgery versus thrombolysis for ischemia of the lower extremity. Ann Surg. 1994;220(3):251-266. PMID: 8092895
- Ouriel K, et al. A comparison of thrombolytic therapy with operative revascularization in the initial treatment of acute peripheral arterial ischemia. J Vasc Surg. 1994;19(6):1021-1030. PMID: 8201702