A cute ischaemic limb


Eric M Bolly is a 66 year old man who presents to A&E with severe left calf and foot pain. This came on suddenly two hours ago. He has a background of atrial fibrillation.

What are the main differentials for an acutely painful calf/foot?

  • Acute ischaemic limb
  • Deep vein thrombosis (usually more subacute, but can be acute)
  • Spinal cord/root compression

Let’s examine him to see which one it is.

On examination, his radial pulse is irregularly irregular.  His left foot is cold and pale. There are no peripheral pulses distal to the popliteal pulse.

There is no edema, erythema or tenderness along the deep veins, making DVT less likely.

There is some altered sensation distally, but no impaired motor function. The altered sensation does not follow a nerve root or peripheral nerve, making root compression less likely.

Given the examination findings, an acute ischaemic limb is most likely.

What causes limb ischaemia?

Two main things – emboli and thombi.

An embolus is anything that travels in the bloodstream and occludes downstream vessels.

A thrombus is a blood clot that forms in the artery/vein and occludes it.

The most common cause of an ischaemic limb is thrombosis. This usually occurs at the site of an atherosclerotic stenosis. Rarer causes of thrombosis include thrombosis of an aneurysm, hypercoagulable states and graft thrombosis.

The most common source for an emboli to cause an acute ischaemic limb is from the heart, such as in atrial fibrillation. Rarer causes of emboli include air, fat, cholesterol or amniotic fluid.

An aortic dissection can also cause limb ischaemic both by emboli and by dissecting off the iliacs. Compartment syndrome (increased tissue pressure within a limited space which compromises tissue function) can also cause an ischaemic limb.

Risk factors wise, the usual atherosclerotic factors apply, with extra emphasis on smoking and diabetes.

How can you tell the limb is acutely ischaemic?

Classically, we look for the 6 P’s:

  • Pain
  • Pallor
  • Pulselessness
  • Perishingly cold
  • Parasthesias
  • Paralysis

Pain is almost universal early on. This pain is severe and usually poorly responsive to analgesia. a non-specific parasthesia can also occur early (two point discrimination especially).

Pulsenessness, pallor and cold can be seen in both acute and chronic ischaemia. This is where history is essential, as well as comparison with the other leg (chronic ischaemias are usually bilateral to at least some extent). You can also look for signs of chronic leg ischaemia, such as hairlessness, waxy shiny skin and arterial ulcers.

Paralysis is a late sign, and suggest irreversibility. Another sign of irreversibility is fixed mottling of the skin. If you are feeling hardcore, have a look at Rutherford’s classification to see when vascular surgeons amputate or revascularise the limb.

Arterial Dopplers can be used to identify whether a pulse is absent or not, although relying on the audio sound alone (without the visual signal) is not fully reliable for confirming adequate arterial flow.

What do we do as junior doctors?

Refer to vascular surgery as soon as this is suspected. They may advise you to start an unfractionated heparin infusion whilst they are on their way. They may wish to consider thrombolysis. They may wish to do an on table angiogram to identify where the lesion is. They may wish to do MR/CT angiography is the limb is not immediately at risk. They may have many wishes, and your job is to give them as much time as possible to fulfil their wishes. You are their genie.

Another case

Mr Thomas Bus is a 67 year old man with a background of diabetes and hypertension. He comes into his GP surgery complaining of pain in the left calf on walking. This typically comes on after about 200 yards. The pain disappears after resting a few minutes.

He asks for a break in the middle of the GP consultation to have a cigarette. He is polite enough to ask the GP if he would like one too, as doctors smoke camels:

What are the main differentials?

  • Intermittent vascular claudication
  • Spinal claudication (marked narrowing of the spinal canal with resulting pressure on exiting nerve roots)
  • Venous claudication
  • Arthritis

What is intermittent vascular claudication?

Remember those 11+ verbal reasoning tests?

Angina is to myocardial infarction as claudication is to the acute ischaemic limb

During times of high demand for oxygen, the poor supply of the lower limb arterial tree is inadequate, leading to pain on exercise that is relieved by rest. 

How can you tell them apart?


Spinal claudication pain is relieved by leaning forward, and better going uphill. Arterial claudication is worse uphill.

Arthritis, usually osteoarthritis of the knee, often comes on weight bearing and there is often pain in the knee itself.

Examination findings

There may be none in intermittent ischaemia if it is mild. As the vascular insufficiency progresses, the patient may develop chronic ischaemic changes (hairlessness, waxy shiny skin). Pulses may be reduced or absent, and the limb may be cool.

An ankle brachial pressure index is usually around 1.0. If it is below 0.9, this suggest arterial insufficiency.

If it is below 0.5, this suggests critical limb ischaemia.

Woah! Critical limb ischaemia? So these patients need to go in?

Critical limb ischaemia is a form of chronic leg ischaemia that has progressed to rest pain, gangrene, ulcers and dependent rubor. The patient may hang their foot over the end of the bed to use gravity to help perfusion. They do not need to go in if this is not acute limb ischaemia, but do need to be seen urgently (within days ideally) by vascular.

How do we treat these?

The first thing to remember is to treat the patient, not just the leg.

Stopping smoking is the single most important thing the patient can do if they smoke. These patients are at risk of stroke and MI, so primary CVD prevention (clopidogrel, statin, BP control, lifestyle changes) applies.

For intermittent claudication (from https://cks.nice.org.uk/peripheral-arterial-disease#!scenariorecommendation:5):

If available, offer a supervised exercise programme to all people with intermittent claudication. This involves:

Two hours of supervised exercise a week for a 3-month period.
Encouraging people to exercise to the point of maximal pain.

If supervised exercise is not available, consider suggesting unsupervised exercise (using clinical judgement and taking into account the person’s motivation and comorbidities).

This involves advice to exercise for approximately 30 minutes three to five times per week, walking until the onset of symptoms, then resting to recover.

Refer for consideration of angioplasty or bypass surgery when:

Advice on the benefits of modifying risk factors has been reinforced, and
A supervised exercise programme has not led to a satisfactory improvement in symptoms.

For critical ischaemia:

Urgently refer to a vascular multidisciplinary team.

Manage pain: Offer paracetamol and either weak or strong opioids, depending on the severity of pain.

The vascular examination

There is a handout for you with a checklist of what to do.