Ruptured aneurysm and acute limb ischaemia

Resuscitation & Emergency Management Protocol

1. Permissive Hypotension: Maintain systolic blood pressure between $70\text{ and }90\text{ mmHg}$ (or mean arterial pressure $50\text{ to }65\text{ mmHg}$) while the patient is conscious and mentally responsive. Aggressive intravenous fluid administration raises hydrostatic pressure, dislodges friable hemostatic clot, dilutes clotting factors, and precipitates uncontrollable exsanguination.
2. Blood access: Activate the local major haemorrhage protocol and give emergency blood when indicated. Group O RhD selection depends on age, sex, reproductive potential and supply; transition to group-specific blood promptly. O-negative is not mandatory for every adult.
3. Immediate Surgical Transfer: Unstable patients must never be transported to the radiology suite for a CT scan. The patient is transferred straight to the vascular operating theatre for immediate exploratory laparotomy or emergency EVAR. Stable or partially stabilized patients may undergo rapid non-contrast or contrast CT angiography only if the vascular surgical team is mobilized and the CT scanner is located immediately adjacent to theatre.

Acute Arterial Limb Ischaemia (ALI)

Acute limb ischaemia is a sudden, critical decrease in limb arterial perfusion threatening tissue viability, defined as onset within 14 days (characteristically hours). Skeletal muscle and peripheral nerves tolerate warm ischaemia poorly: irreversible muscle necrosis and permanent nerve paralysis begin after 4 to 6 hours of complete arterial interruption.

The Classic "6 Ps"

• Pain: Earliest, most prominent symptom; severe, constant, starting distally and progressing proximally; refractory to simple analgesia.
• Pallor: Initial waxy, pale skin from intense arterial spasm, later transitioning to mottled, non-blanching cyanosis.
• Pulselessness: Absent palpable pulses and absent handheld Doppler signals distally.
• Paresthesia: Numbness, tingling, or loss of two-point discrimination. Large sensory nerve fibers are exquisitely vulnerable to ischaemic hypoxia; paresthesia is the earliest objective neurological marker of critical ischemia.
• Perishingly cold (Poikilothermia): The affected extremity becomes cold to the touch and adopts ambient room temperature.
• Paralysis: Inability to move toes or perform ankle dorsiflexion ('foot drop'). Indicates deep ischemic necrosis of intrinsic muscle groups and motor nerve failure—an ominous sign of advanced, threatened viability.

Aetiology: Arterial Embolism vs In-Situ Thrombosis

• Onset: Arterial Embolism (~40%): Sudden, dramatic (seconds to minutes); In-Situ Arterial Thrombosis (~60%): Insidious, stuttering over hours or days
• Underlying History: Arterial Embolism (~40%): Atrial fibrillation, recent MI, valve prosthesis; In-Situ Arterial Thrombosis (~60%): Longstanding peripheral artery disease, claudication
• Prior Claudication: Arterial Embolism (~40%): Absent; In-Situ Arterial Thrombosis (~60%): Frequently present
• Collateral Vessels: Arterial Embolism (~40%): Absent (causes severe, abrupt ischaemia); In-Situ Arterial Thrombosis (~60%): Extensive preexisting collaterals soften severity
• Physical Examination: Arterial Embolism (~40%): Normal contralateral peripheral pulses; In-Situ Arterial Thrombosis (~60%): Diminished/absent contralateral pulses, trophic skin changes
• Most Common Site: Arterial Embolism (~40%): Femoral artery bifurcation (40%), aortic bifurcation; In-Situ Arterial Thrombosis (~60%): Superficial femoral artery, popliteal artery, grafts

Rutherford Classification of Acute Limb Ischaemia

• Category I (Viable): Limb is not immediately threatened. No sensory loss, no muscle weakness. Handheld Doppler reveals audible arterial and venous signals.
• Category IIa (Marginally Threatened): Salvageable if promptly treated. Minimal sensory loss limited to toes; no motor weakness. Arterial Doppler signals are often inaudible; venous Doppler signals remain audible.
• Category IIb (Immediately Threatened): Salvageable only with immediate emergency revascularisation. Sensory loss extends beyond the digits (foot/calf); mild-to-moderate motor weakness (impaired toe/foot dorsiflexion). Arterial Doppler inaudible; venous Doppler audible.
• Category III (Irreversible): Permanent tissue loss and nerve damage. Profound cutaneous anaesthesia, fixed mottling, rigid muscular contracture (rigor mortis of muscle). Both arterial and venous Doppler signals are completely silent. Primary surgical amputation is indicated; emergent revascularisation is contraindicated as it triggers fatal systemic reperfusion injury.

Emergency Management

1. Immediate Systemic Anticoagulation: Administer an immediate intravenous bolus of unfractionated heparin 5000 units (or $80\text{ units/kg}$), followed by a continuous infusion targeting an activated partial thromboplastin time (aPTT) of 1.5 to 2.5 times control. Heparin prevents propagation of secondary thrombus into distal microvascular runoff beds.
2. Positioning & Supportive Measures: Keep the limb dependent (slightly below heart level) to utilize gravity for perfusion; never elevate the limb. Pad the foot with cotton wool to prevent pressure sores; avoid direct heating or cooling.
3. Emergent Revascularisation: Mobilize the vascular surgical team immediately:
   • Surgical Embolectomy: Performed under local or light general anaesthesia using a balloon-tipped Fogarty catheter introduced through a common femoral or brachial arteriotomy.
   • Catheter-Directed Thrombolysis (CDT): Infusion of tissue plasminogen activator (tPA / alteplase) directly into the thrombus over 12 to 24 hours, indicated for Category IIa in-situ thrombosis with patent runoff.
   • Surgical Bypass or Endovascular Stenting: Required for thrombotic occlusions with underlying chronic atherosclerotic disease.

Reperfusion Injury & Compartment Syndrome

Re-establishing arterial flow into an ischaemic extremity induces an acute inflammatory cascade, reactive oxygen species generation, capillary hyperpermeability, and profound muscle swelling within rigid fascial envelopes.

• Reperfusion Compartment Syndrome: Most common in the lower leg (which contains four distinct compartments: anterior, lateral, superficial posterior, and deep posterior). Characterized by severe, unrelenting pain out of proportion to exam, exquisitely aggravated by passive stretching of the calf muscles, and tense, woody induration. Palpable distal pulses may persist because intracompartmental pressures rarely exceed systolic arterial pressure.
• After limb revascularisation: Monitor for reperfusion injury, hyperkalaemia, rhabdomyolysis and compartment syndrome. Fasciotomy is indicated by clinical risk and findings, not automatically after every six-hour delay. IV bicarbonate solely to alkalinise urine is not routine rhabdomyolysis care.
• Reperfusion injury: Monitor potassium, ECG, CK, kidney function and compartment signs. Give fluids according to perfusion and overload risk, and treat serious hyperkalaemia promptly. Routine urine alkalinisation is not established standard care for every rhabdomyolysis case.

Primary references (checked 7 October 2026): Australian critical bleeding guideline.