Acute limb ischaemia

Surgical approach

• Time-critical limb salvage: decision based on viability (Rutherford classification) and imaging availability
  • Viable / marginally threatened: urgent imaging (often CTA) then revascularisation
  • Immediately threatened: proceed to theatre without delay (imaging only if it will not delay)
  • Irreversible: primary amputation; avoid reperfusion of necrotic limb
• Typical operative options (depend on cause and level)
  • Embolectomy (Fogarty balloon) for embolus; may include on-table angiography
  • Catheter-directed thrombolysis (e.g. alteplase) for thrombosis in selected stable cases (often in IR suite)
  • Bypass grafting (e.g. fem-pop) or endarterectomy/stenting for in-situ thrombosis/critical stenosis
  • Fasciotomy if prolonged ischaemia/reperfusion risk or compartment syndrome
  • Amputation if non-viable limb or life-threatening sepsis/metabolic derangement
• Perioperative anticoagulation
  • IV unfractionated heparin as soon as diagnosis suspected unless contraindicated (e.g. active bleeding, intracranial haemorrhage)
  • Intraoperative heparinisation often used for open revascularisation; coordinate with anaesthesia (neuraxial implications)

Anaesthetic management (overview)

• Type of anaesthesia: GA commonly; regional may be appropriate in selected cases (but consider anticoagulation, urgency, ability to tolerate lying flat, and need for fasciotomy)
  • Neuraxial (spinal/epidural): useful for infra-inguinal surgery and analgesia but often limited by urgent heparin and antiplatelets; follow ASRA/RA-UK timing guidance
  • Peripheral blocks (e.g. femoral + sciatic): may be an option for distal procedures; beware masking compartment syndrome pain post-op
• Airway: ETT usually (full stomach, sepsis/physiological derangement, long/variable duration); SGA only if low aspiration risk and short stable case
  • RSI often appropriate: opioids/induction titrated to haemodynamics; consider ketamine/etomidate in shock
• Duration: highly variable (≈1–4+ h); can extend with bypass, fasciotomy, complex endovascular work
  • Expect unpredictability; plan for invasive monitoring and temperature control
• How painful: moderate–severe (ischaemic pain pre-op; significant post-op pain especially with fasciotomy/amputation)
  • Multimodal analgesia; consider catheter techniques if anticoagulation permits; avoid hypotension compromising perfusion
• Monitoring/lines: arterial line early; 2 large-bore IV; consider CVC if vasoactive infusions/poor access; urinary catheter
  • Point-of-care: ABG/VBG, lactate, K+, glucose; consider TEG/ROTEM if bleeding/major surgery
• Key intra-op risks: reperfusion syndrome (acidosis, hyperkalaemia, hypotension), arrhythmias, bleeding (heparin/thrombolysis), hypothermia, AKI, compartment syndrome
  • Have calcium, insulin/dextrose, sodium bicarbonate (selected), vasopressors ready; communicate before clamp release

Definition and importance

• Acute limb ischaemia: sudden decrease in limb perfusion threatening limb viability (typically <14 days symptom onset)
• High morbidity/mortality: risk of limb loss, systemic complications from reperfusion, and underlying cardiovascular disease

Aetiology

• Embolus (classically sudden onset, no prior claudication): AF, mural thrombus post-MI, valvular disease, aneurysm
• In-situ thrombosis (often on background PAD): plaque rupture, low flow states, dehydration, hypercoagulable states
• Graft/stent occlusion: thrombosis or technical failure
• Trauma/iatrogenic: arterial injury, dissection, closure device complication
• Other: aortic dissection, popliteal aneurysm thrombosis, compartment syndrome causing secondary ischaemia

Clinical features and classification

• Symptoms/signs: the 6 Ps
  • Pain (often severe), Pallor, Pulselessness, Paraesthesia, Paralysis, Poikilothermia (cold)
• Rutherford classification (practical perioperative relevance)
  • I Viable: no sensory/motor loss; arterial/venous Doppler audible → urgent but not immediate
  • IIa Marginally threatened: minimal sensory loss (toes), no motor deficit; arterial Doppler often inaudible → urgent revascularisation
  • IIb Immediately threatened: more than toes sensory loss, mild–moderate motor deficit → immediate revascularisation (time critical)
  • III Irreversible: profound anaesthesia, paralysis/rigor; major tissue loss inevitable → primary amputation; reperfusion may be fatal

Initial management (ED/ward) relevant to anaesthesia

• Resuscitate: ABCDE, oxygen if needed, IV access, analgesia (opioid titration), treat sepsis/shock
• Anticoagulation: IV UFH bolus then infusion unless contraindicated; reduces thrombus propagation and improves microcirculation
• Limb care: keep limb dependent (not elevated), keep warm (systemically), avoid external heat to limb (burn risk), no compression
• Investigations: FBC, U&E/creatinine, coagulation, group & save/crossmatch, ABG/VBG (lactate, K+), ECG, troponin if indicated
• Imaging: CTA or duplex if it will not delay limb-saving intervention; consider renal function/contrast nephropathy risk

Preoperative assessment (anaesthetic focus)

• Assess urgency and limb viability; clarify planned procedure (embolectomy vs bypass vs thrombolysis vs amputation) and location (theatre vs IR)
• Cardiovascular risk: ALI patients often have significant IHD/CCF/AF; obtain baseline ECG, consider echo if time and instability
• Physiology: dehydration, sepsis, metabolic acidosis, hyperkalaemia (especially with prolonged ischaemia), rhabdomyolysis
• Anticoagulants/antiplatelets: document timing/doses (DOAC/warfarin/LMWH/UFH, aspirin, clopidogrel); impacts neuraxial and bleeding
• Aspiration risk: pain, opioids, emergency surgery → treat as full stomach; plan RSI where appropriate

Intraoperative management

• Induction: haemodynamically stable induction; consider etomidate/ketamine in shock; avoid hypotension that worsens limb and end-organ perfusion
• Ventilation: maintain normocapnia and oxygenation; avoid severe hypocapnia (vasoconstriction) and acidosis (arrhythmogenic, worsens pulmonary vasoconstriction)
• Haemodynamics: aim adequate MAP for coronary/cerebral perfusion and collateral limb flow; vasopressors often required (noradrenaline ± vasopressin)
• Fluids/blood: balanced crystalloids; avoid overload in cardiac disease; crossmatch if bypass/bleeding risk; cell salvage may be useful in open surgery
• Temperature: active warming; hypothermia worsens coagulopathy and vasoconstriction
• Analgesia: opioid titration; consider regional where safe; ketamine infusion can help severe ischaemic pain; plan post-op analgesia early
• Antibiotics: per local vascular protocol (especially if graft, fasciotomy, or amputation)

Reperfusion: pathophysiology and management

• Mechanism: washout of anaerobic metabolites and cellular contents from ischaemic limb → systemic acidosis, hyperkalaemia, myoglobin, inflammatory mediators
• Clinical effects at reperfusion: hypotension (vasodilation), brady/ventricular arrhythmias, cardiac arrest, pulmonary oedema (inflammatory), worsening coagulopathy
• Preparation before reperfusion/clamp release
  • Inform anaesthetist before restoring flow; ensure A-line waveform and recent ABG (K+, pH, lactate)
  • Optimise volume status and vasopressor readiness; consider increasing FiO2 temporarily
  • Treat hyperkalaemia proactively if suspected/prolonged ischaemia: calcium chloride/gluconate, insulin/dextrose, salbutamol; consider bicarbonate if severe acidaemia
• Rhabdomyolysis/AKI prevention: maintain perfusion, avoid nephrotoxins, monitor urine output; consider alkalinisation/diuresis only with senior input and clear indication (evidence mixed)

Compartment syndrome (perioperative relevance)

• Risk increased with prolonged ischaemia, reperfusion, thrombolysis, aggressive fluid resuscitation, and combined arterial/venous injury
• Diagnosis: pain out of proportion, pain on passive stretch, tense compartments, sensory changes; pulses may be present
• Anaesthetic pitfall: dense regional analgesia may mask evolving compartment syndrome; ensure robust surveillance plan if blocks used
• Treatment: urgent fasciotomy; anticipate blood loss, fluid shifts, and significant post-op pain

Postoperative care

• Destination: HDU/ICU often appropriate (reperfusion risk, vasopressors, metabolic derangement, major comorbidity, fasciotomy/amputation)
• Monitoring: serial ABGs (K+, pH, lactate), ECG monitoring for arrhythmias, urine output/creatinine, CK, coagulation if thrombolysis/heparin
• Analgesia: multimodal; consider PCA; regional catheters only with anticoagulation plan and neurovascular checks
• Anticoagulation/antiplatelets: continue per vascular/haematology plan; be explicit about neuraxial catheter removal timing if used