Acute Limb Ischaemia — CST Interview Station Answer

Acute limb ischaemia is a sudden fall in limb perfusion that threatens viability, and at the CST management and clinical station the answer is the six Ps, a Rutherford grade, immediate intravenous heparin and an immediate vascular referral. According to the European Society for Vascular Surgery 2020 guideline, therapeutic anticoagulation with unfractionated heparin should start once the diagnosis is made, and revascularisation should be prompt whenever the limb is threatened. The grade decides the pace.

Key takeaways

The six Ps are pain, pallor, pulselessness, perishingly cold, paraesthesia and paralysis; the last two mean the limb is threatened
The Rutherford classification grades the limb as I viable, IIa marginally threatened, IIb immediately threatened, or III irreversible, using sensory loss, muscle weakness and arterial and venous Doppler signals
A Rutherford IIb limb has sensory loss beyond the toes with rest pain, mild to moderate weakness and an inaudible arterial Doppler, and is salvageable only with immediate revascularisation
ESVS 2020 recommends intravenous unfractionated heparin, a bolus then an infusion, as soon as acute limb ischaemia is diagnosed unless there is a serious contraindication
ESVS 2020 says catheter-directed thrombolysis is considered for Rutherford IIa and may be considered for IIb, and asks for access to a hybrid theatre with a team offering open and endovascular options
A class III limb with profound anaesthesia, paralysis and inaudible arterial and venous signals faces major tissue loss or permanent nerve damage whatever is done

How do I recognise acute limb ischaemia?

Recognise acute limb ischaemia by the six Ps: pain, pallor, pulselessness, a perishingly cold limb, paraesthesia and paralysis, compared against the other leg.

The first four are present in most cases and tell you the limb is ischaemic. The last two, paraesthesia and paralysis, tell you the nerves and muscle are failing, and they move the patient from urgent to immediate.

Ask about the onset, because an embolus gives a sudden, complete picture in a patient with atrial fibrillation or a recent infarct, whereas thrombosis on chronic disease is slower and the other leg often shows claudication signs.

How do I assess a patient with an acutely ischaemic limb?

Assess an acutely ischaemic limb with the CCrISP three stages: immediate ABCDE management, then a full assessment that grades the limb, then a plan that names the vascular surgeon and the time.

In the immediate stage give oxygen, secure access, send bloods including a venous gas with lactate, potassium and creatine kinase, and an ECG for atrial fibrillation. The limb is the emergency, but the heart is often the cause.

In the full assessment, examine sensation, power and both Doppler signals in the affected limb and record the findings with a time, because the Rutherford grade you give now is the baseline everyone compares against.

What is the Rutherford classification of acute limb ischaemia?

The Rutherford classification grades acute limb ischaemia into four categories by sensory loss, muscle weakness and arterial and venous Doppler signals, and each category carries a prognosis.

Class I, viable: not immediately threatened; no sensory loss, no weakness, audible arterial and venous Doppler
Class IIa, marginally threatened: salvageable if promptly treated; sensory loss none or minimal in the toes, no weakness, arterial Doppler inaudible, venous audible
Class IIb, immediately threatened: salvageable with immediate revascularisation; sensory loss beyond the toes with rest pain, mild to moderate weakness, arterial inaudible, venous audible
Class III, irreversible: major tissue loss or permanent nerve damage inevitable; profound anaesthesia and paralysis, arterial and venous Doppler both inaudible

The panel wants the grade said as a sentence: this is a Rutherford IIb limb because there is sensory loss above the toes and weakness, so it needs revascularisation now.

What is the immediate management of acute limb ischaemia?

The immediate management of acute limb ischaemia is intravenous unfractionated heparin, analgesia, oxygen, fluids, and an immediate referral to the vascular surgeon on call.

According to ESVS 2020, therapeutic anticoagulation with intravenous unfractionated heparin, a bolus followed by a continuous infusion, should be given once the diagnosis is established, unless there is a significant contraindication such as active bleeding or recent surgery.

Heparin stops propagation of the clot and protects the collaterals while the plan is made. Keep the limb level, not elevated, and do not apply heat.

Which investigations should I request, and should they delay theatre?

Request a venous gas, full blood count, renal function, clotting, creatine kinase, a group and save and an ECG, and arrange imaging only where it will not delay revascularisation of a threatened limb.

Imaging is duplex ultrasound or CT angiography, chosen by the vascular team. For a Rutherford IIb limb the guideline's word is immediate, so the surgeon may take the patient to theatre with on-table imaging rather than wait.

ESVS 2020 asks that patients have access to a hybrid theatre, or an operating theatre with a C-arm, staffed by a team able to offer open or endovascular treatment in a single procedure. Name that as where the patient is going.

When does an ischaemic limb need immediate revascularisation?

An ischaemic limb needs immediate revascularisation when it is Rutherford IIb, and prompt revascularisation when it is IIa; the ESVS 2020 update states revascularisation should be performed promptly whenever the viability of the limb is threatened.

The options are open embolectomy or bypass, catheter-directed thrombolysis, and mechanical thrombectomy, alone or combined. ESVS 2020 says thrombolysis is considered for IIa and may be considered for IIb, where the slower onset is the cost.

For a class III limb the tissue is dead, and revascularisation risks reperfusion injury with hyperkalaemia, myoglobinuria and acidosis. Primary amputation is a consultant decision to be raised, not avoided.

What are the complications of reperfusion?

The complications of reperfusion are compartment syndrome, hyperkalaemia, myoglobinuria with acute kidney injury, and a metabolic acidosis, and a surgical SHO should be watching for all four after revascularisation.

Say that you would monitor potassium and the gas, keep the patient well filled with a catheter in place, and examine the calf for a tense compartment with pain on passive stretch. Fasciotomy is often done at the time of revascularisation for this reason.

Who do I escalate acute limb ischaemia to?

Escalate acute limb ischaemia to the vascular surgical registrar immediately, and to your own consultant, with the Rutherford grade, the time of onset and the heparin already running.

If your hospital has no vascular service, the call goes to the regional vascular centre and the transfer is arranged as an emergency. Involve anaesthetics early, because a IIb limb is going to theatre.

How this comes up at the CST interview

Acute limb ischaemia is set as a patient in atrial fibrillation with a sudden cold, painful leg, and the panel is listening for the Rutherford grade, immediate heparin and a named call within your first minute.

Follow-ups include what changes if the foot is now insensate and paralysed, what reperfusion injury looks like on the ward, and how you would discuss amputation with the patient.

The coresurgeryinterview bank includes a scored acute limb ischaemia scenario among its 299 questions: /Question-Bank/Sample-Questions.

FAQ

What are the six Ps of acute limb ischaemia?

Pain, pallor, pulselessness, perishingly cold, paraesthesia and paralysis. The first four indicate ischaemia; paraesthesia and paralysis indicate nerve and muscle failure and mark a threatened limb that needs immediate revascularisation.

What is a Rutherford IIb limb?

An immediately threatened limb: sensory loss beyond the toes with rest pain, mild to moderate muscle weakness, an inaudible arterial Doppler and an audible venous Doppler. It is salvageable only with immediate revascularisation.

Should I give heparin before the vascular team has seen the patient?

Yes. ESVS 2020 recommends intravenous unfractionated heparin, a bolus then an infusion, once acute limb ischaemia is diagnosed, unless there is a serious contraindication such as active bleeding in the previous 24 to 48 hours or recent surgery.

Is thrombolysis an option in acute limb ischaemia?

ESVS 2020 says catheter-directed thrombolysis is considered for Rutherford IIa and may be considered for IIb, often combined with mechanical thrombectomy. Its slower onset makes it less suitable the more threatened the limb.

What happens if a Rutherford III limb is revascularised?

The tissue is already non-viable, so revascularisation risks reperfusion injury with hyperkalaemia, myoglobinuria, acidosis and death, without saving the limb. Primary amputation is discussed at consultant level.

Why does the ECG matter in a cold leg?

Because embolism from atrial fibrillation or a recent myocardial infarction is a leading cause. The ECG finds the source, guides anticoagulation after discharge, and tells the anaesthetist what they are dealing with.

Acute Limb Ischaemia: the Six Ps and Time to Theatre