Acute Limb Ischaemia

🚨 ALI = sudden reduction in arterial perfusion to a limb → time-critical emergency. 🎯 Priorities: call vascular early, assess viability (Rutherford), heparinise unless contraindicated, relieve pain, and revascularise urgently if threatened.

⚡ Initial Management (do this first)

• 📞 Escalate immediately: bleep vascular surgery (and anaesthetics/ICU if shocked). Document time of onset/last-known-well.
• 🧍 Protect the limb: keep dependent (not elevated), keep warm, remove tight dressings/splints, and avoid compression.
• 🧠 Rapid A–E + monitoring: ECG, SpO₂, BP; oxygen only if hypoxic. Insert 2 wide-bore IV cannulas; give IV fluids if shocked (reassess frequently).
• 😖 Analgesia: titrated IV opioid (e.g., morphine) + antiemetic; severe pain is common and does not exclude viability.
• 🦵 Assess & record limb viability: colour, temperature, cap refill, sensation, motor; palpate pulses and use Doppler for arterial + venous signals → classify Rutherford.
• 💉 Anticoagulate early (unless contraindicated): IV unfractionated heparin (typical initial bolus 5,000 units then infusion per local protocol/vascular advice).
  Quick contraindication check: active major bleeding, recent haemorrhagic stroke, severe uncontrolled hypertension, etc.
• 🧪 Bloods: FBC, U&E/creatinine, LFTs, clotting, CK, VBG/ABG (lactate), glucose, CRP, group & save ± crossmatch.
• 🔎 Identify cause without delaying treatment: ECG for AF/MI; focused history for embolic source (AF, recent MI), recent vascular intervention, trauma, thrombophilia/malignancy.
• 🖥️ Imaging: if limb is viable or IIa and it won’t delay definitive care → CTA or duplex for planning.
  If IIb (immediately threatened), prioritise urgent revascularisation over imaging delays.

🧠 Why urgency matters: ischaemia → anaerobic metabolism (↑ lactate), endothelial injury and microvascular thrombosis. After reperfusion, toxins and myoglobin can surge into circulation → hyperkalaemia, acidosis, rhabdomyolysis, AKI; locally, swelling can trigger compartment syndrome.

📖 About

• 💥 ALI = sudden ↓ arterial blood supply → vascular emergency.
• ⏱️ Threatened limbs (IIa/IIb) need urgent restoration of flow; IIb is “act now”.
• 🧲 Embolus often causes sudden severe symptoms in a previously well limb; thrombosis occurs on background PAD and may have some collaterals.

🩺 Aetiology

• 🧠 Embolic (sudden): AF, mural thrombus post-MI, ventricular aneurysm, endocarditis.
• 🧱 Thrombotic (on PAD): in-situ thrombosis on atherosclerotic plaque, bypass graft thrombosis.
• 🛠️ Iatrogenic/traumatic: catheter-related occlusion, dissection, limb trauma.

🚨 Clinical Features - the “6 Ps”

• 💥 Pain (often severe, early)
• ⚪ Pallor
• 🫱 Pulselessness
• ❄️ Perishing cold
• 🔌 Paraesthesia (sensory loss)
• ⛔ Paralysis (late = poor prognostic sign)

📊 Rutherford Classification (Acute Limb Ischaemia)

🧪 Investigations (don’t delay the threatened limb)

• 🦵 Handheld Doppler: absent arterial signal supports ALI; keep reassessing.
• 🖥️ CTA / duplex: define level/length of occlusion if limb viable or IIa and imaging won’t delay treatment.
• 🚫 Rule: never delay revascularisation for imaging in IIb.

🛠️ Definitive management pathways (what vascular may do)

• ✂️ Embolectomy (often for embolic occlusion).
• 🩹 Bypass / thrombectomy (often for thrombosis on PAD).
• 💉 Catheter-directed thrombolysis (selected cases; usually not if immediately threatened).
• 🦵 Amputation if limb non-viable (category III) to prevent life-threatening reperfusion/necrosis complications.
• 🕊️ Palliation may be appropriate in frail/dying patients where intervention is not in the patient’s interests-focus on comfort and symptom control.

⚠️ Complications to anticipate

• ⚡ Hyperkalaemia (muscle necrosis/reperfusion) → ECG monitoring and treat rapidly if present.
• 📈 Compartment syndrome → escalating pain (esp. on passive stretch), tense compartments → urgent fasciotomy.
• 🩸 Rhabdomyolysis → myoglobinuria/AKI → fluids, close renal/electrolyte monitoring.
• 🫀 Systemic deterioration after reperfusion: acidosis, arrhythmias, shock.