Twelve Hours of Ischaemia in a Patient With an Aneurysm
Mr D is 76 and presents 11 hours after the sudden onset of a cold, painful right leg. He has atrial fibrillation and takes no anticoagulant. The right femoral pulse is palpable, but there are no popliteal or pedal Doppler signals. The leg is pale with mottled skin to mid-calf, the calf is tense, sensation over the dorsum of the foot is reduced, and he cannot dorsiflex his ankle or toes. He is confused and in fast atrial fibrillation at 130/min; blood pressure is 150/90 mmHg. Creatinine is 165 µmol/L and potassium 5.4 mmol/L. The CT done in the emergency department also shows a 6.2 cm infrarenal abdominal aortic aneurysm, and he had a left femoropopliteal bypass four years ago.
1. Classify the limb, and describe your immediate management, including the choice of anaesthesia and procedure.
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Classification Rest pain, sensory deficit and a motor deficit with inaudible arterial and venous Doppler signals - Rutherford IIb, an immediately threatened limb. Features that would make it irreversibly ischaemic (Rutherford III) include muscle rigor, fixed mottling, profound paralysis and absent capillary refill; none is clearly present, so the limb is salvageable if treated now.
Immediate actions
- Theatre within the hour. No further imaging; the CT already performed should not be repeated.
- Unfractionated heparin 80 U/kg intravenously, unless contraindicated.
- Treat the potassium with calcium gluconate, insulin-dextrose and salbutamol, and monitor continuously - reperfusion will push it higher.
- Consent explicitly for possible amputation.
- Correct the rate in atrial fibrillation, but do not delay surgery for it.
Anaesthesia and operation
- Local or regional anaesthesia with sedation is preferable to general anaesthesia in a confused, fast-AF patient.
- Common femoral arteriotomy with Fogarty balloon embolectomy of the superficial femoral, profunda and popliteal segments, plus on-table completion angiography.
- On-table angiography is the decision point: a clean embolus with good run-off ends the operation; a thrombosed, diseased vessel or a failed embolectomy requires bypass, and the previous contralateral bypass tells you his conduit and disease pattern are poor.
- If the leg is clearly irreversible, primary amputation is kinder than a futile revascularisation.
2. What will you monitor for after revascularisation, and how do you decide about a fasciotomy?
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Reperfusion is the next threat Eleven hours of ischaemia means a substantial load of potassium, myoglobin, lactate and oxygen free radicals re-entering the circulation.
Monitor and treat:
- Hyperkalaemia - continuous ECG, potassium every 4–6 hours; calcium, insulin-dextrose, and dialysis if refractory or if acute kidney injury develops.
- Myoglobinuria - aggressive balanced crystalloid to maintain urine output of 1–2 mL/kg/h; consider sodium bicarbonate to alkalinise the urine, though evidence is weak.
- Acidosis and arrhythmia, particularly with the fast atrial fibrillation; correct magnesium.
- Respiratory failure (ARDS) and cardiac depression - anticipate ICU admission.
- Compartment syndrome of the calf and thigh.
Fasciotomy - the judgement Do not wait for absent pulses (they are already absent) or for a late neurological sign. The reliable signals are:
- Pain on passive stretch that is disproportionate to the wound,
- A tense, woody compartment,
- Rising creatine kinase and worsening acidosis,
- A compartment pressure within 30 mmHg of diastolic pressure.
In practice: if ischaemia exceeds six hours, the calf is already tense in theatre, or the limb was blue and swollen before revascularisation, perform a prophylactic four-compartment fasciotomy at the same sitting. A delayed fasciotomy after muscle necrosis means amputation, not salvage. If in doubt, release.
3. What do you do about the 6.2 cm aneurysm, and how does his confusion influence your plan?
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The aneurysm is a separate problem At 6.2 cm it meets the size threshold for repair (about 5.5 cm in men), and left untreated the annual rupture risk is substantial. But it is not the emergency today, and a simultaneous aortic repair in a patient with acute limb ischaemia, hyperkalaemia, a likely myocardial insult and a fast atrial fibrillation would be a fatal combination.
Sequence:
- Treat the limb.
- Once he has recovered and been discharged, obtain a CT angiogram of the aorta to assess anatomy for endovascular repair, which is preferred in a patient of this age and cardiac risk.
- Repair electively within weeks to a couple of months, not years - a 6.2 cm sac is not to be watched indefinitely.
- If he develops abdominal or back pain with hypotension, the aneurysm becomes the emergency and the limb becomes secondary.
The confusion It is a red flag, not background noise. Causes to exclude immediately: embolic stroke from the atrial fibrillation (which would change anticoagulation and prognosis), sepsis, hypoxia, and hypoperfusion. Examine the pupils, tone and plantar responses, check glucose and oxygen, and obtain a CT head. If he has had a stroke, the risk–benefit of full heparinisation and the timing of aneurysm repair both change, and the decision should be made jointly with a stroke physician rather than by the vascular team alone.