Acutely Ischaemic Limb

Question 1

… … … refers to a sudden decrease in blood supply resulting in ischaemic injury to the lower limbs.

Answer 1

Acute limb ischaemia (ALI) refers to a sudden decrease in blood supply resulting in ischaemic injury to the lower limbs.

Question 2

ALI is caused by sudden obstruction to arterial flow (venous obstruction can cause ALI but is rare) most commonly secondary to embolism or thrombosis. In the setting of complete ischaemia, necrosis results after around … hours

Answer 2

ALI is caused by sudden obstruction to arterial flow (venous obstruction can cause ALI but is rare) most commonly secondary to embolism or thrombosis. In the setting of complete ischaemia, necrosis results after around 6 hours.

Question 3

Acute limb ischaemia is most commonly caused by … or ….

Answer 3

Acute limb ischaemia is most commonly caused by embolisation or thrombosis.

Question 4

Arterial thrombosis is a common cause of …. This normally occurs in a vessel with pre-existing atherosclerosis. The rupture of an atherosclerotic plaque occurs when the cap breaks off exposing a rough and thrombogenic surface resulting in further relatively rapid thrombus progression.

Answer 4

Arterial thrombosis is a common cause of ALI. This normally occurs in a vessel with pre-existing atherosclerosis. The rupture of an atherosclerotic plaque occurs when the cap breaks off exposing a rough and thrombogenic surface resulting in further relatively rapid thrombus progression.

Question 5

… refers to a solid deposit (typically a piece of thrombus) traveling from its source (typically central) and lodging in a distal vessel. This often occurs from a cardiac source of thrombus (e.g. secondary to AF or an MI) or one associated with a proximal aneurysm (e.g. AAA, popliteal).

Answer 5

Embolisation refers to a solid deposit (typically a piece of thrombus) traveling from its source (typically central) and lodging in a distal vessel. This often occurs from a cardiac source of thrombus (e.g. secondary to AF or an MI) or one associated with a proximal aneurysm (e.g. AAA, popliteal).

Question 6

Paradoxical embolisation refers to emboli from the venous circulation that cause arterial obstruction. They are termed ‘paradoxical’ as theoretically they should not occur, any venous embolism should travel to the heart before becoming lodged in the pulmonary circulation. However, in patients with cardiac defects (e.g. atrial septal defect), emboli can pass directly from the right side of the heart to the left. They commonly cause strokes but can also cause ….

Answer 6

Paradoxical embolisation refers to emboli from the venous circulation that cause arterial obstruction. They are termed ‘paradoxical’ as theoretically they should not occur, any venous embolism should travel to the heart before becoming lodged in the pulmonary circulation. However, in patients with cardiac defects (e.g. atrial septal defect), emboli can pass directly from the right side of the heart to the left. They commonly cause strokes but can also cause ALI.

Question 7

Other causes of acute limb ischaemia? (Apart from thrombosis and emboli)

Answer 7

Acute aortic dissection: can result in impaired blood supply to the limbs (as well as the rest of the body).
Trauma: a traumatic arterial injury can impair blood supply.
Phlegmasia cerulea dolen: a rare complication of a DVT in which venous congestion results in oedema and impaired blood supply to tissue.

Question 8

What are the two most significant risk factors for developing PAD?

Answer 8

Smoking and diabetes
Others include:
Age
Hypertension
Hyperlipidaemia
Obesity

Question 9

Classically the 6 …s are used to describe the features of acute limb ischaemia.

Answer 9

Classically the 6 P’s are used to describe the features of acute limb ischaemia.

The six P’s of acute limb ischaemia are:

Pain
Pulseless
Pallor
Paralysis
Paraesthesia
Perishingly cold

Question 10

The six P’s of acute limb ischaemia are:

Answer 10

The six P’s of acute limb ischaemia are:

Pain
Pulseless
Pallor
Paralysis
Paraesthesia
Perishingly cold

Question 11

The … classification can be used to grade and guide management in acute limb ischaemia.

Answer 11

The Rutherford classification can be used to grade and guide management in acute limb ischaemia.

Question 12

The Rutherford classification can be used to grade and guide management in … … ischaemia.

Answer 12

Question 13

Bedside obs in acute limb ischaemia

Answer 13

Observations
ECG (in particular lookout for arrhythmias like AF)
BM (blood sugar)

Question 14

Bloods in suspected acute limb ischaemia

Answer 14

FBC
U&Es
LFTs
Clotting screen
Group and save
VBG/ABG (obtain a lactate measurement)
Consider a thrombophilia screen

Question 15

Imaging options for acute limb ischaemia

Answer 15

Duplex ultrasound (DUS): a non-invasive technique that allows visualisation of the arteries and assessment of stenosis.

CT angiogram (CTA): a non-invasive technique that uses IV contrast to allow visualisation of the arteries and any narrowing/occlusion.

Digital subtraction angiography (DSA): an invasive technique that utilises catheter-guided contrast injection (into the vessel of interest) combined with fluoroscopy (a form X-ray imaging in which multiple pictures are taken over a short period of time). Digital subtraction removes the background image to isolate the contrast and vessels.

Other imaging may be obtained to identify the underlying cause of the ALI. An echocardiogram is helpful if a cardiac origin of embolism is suspected. This is not as urgent as other diagnostic imaging or revascularisation but can occur following appropriate treatment.

Question 16

The rate of amputation in acute limb ischaemia is linked to ‘time to …’, as such prompt recognition and management are key.

Answer 16

The rate of amputation is linked to ‘time to reperfusion’, as such prompt recognition and management are key.

Question 17

Initial management of acute limb ischaemia

Answer 17

Initial management involves symptomatic relief (analgesia for the pain) and heparin (an anticoagulant). Heparin improves patients symptoms and is thought to prevent proximal or distal propagation of thrombus.

Question 18

Initial management of acute limb ischaemia involves symptomatic relief (analgesia for the pain) and heparin (an anticoagulant). Heparin improves patients symptoms and is thought to prevent proximal or distal propagation of thrombus.

What is required following this?

Answer 18

Following this revascularisation is required - this refers to restoring adequate blood supply to the ischaemic tissue. The general treatment options and terms to be aware of are:

Question 19

Revascularisation is required in acute limb ischaemia - this refers to restoring adequate blood supply to the ischaemic tissue. The general treatment options and terms to be aware of are: (4)

Answer 19

Intra-arterial catheter thrombolysis: a percutaneous technique that involves obtaining vascular access with a catheter and injecting a thrombolytic (clot-busting) agent directly into the affected vessel. Alteplase is a commonly used agent. This is generally suitable for less severe cases without neurological deficit.
Percutaneous mechanical thrombectomy/thrombo-aspiration: these are percutaneous techniques that allow for the removal of the thrombus. They can be combined with catheter-directed thrombolysis.
Surgical thrombectomy: open surgical techniques are still commonly required. One option is surgical thrombectomy in which the vessel is opened and thrombus removed.
Surgical bypass: bypass involves placing a graft connecting the vessel proximal to the obstruction to the vessel distal to it.

Question 20

Intra-arterial catheter thrombolysis - what is this?

Answer 20

a percutaneous technique that involves obtaining vascular access with a catheter and injecting a thrombolytic (clot-busting) agent directly into the affected vessel. Alteplase is a commonly used agent. This is generally suitable for less severe cases without neurological deficit.

Question 21

Percutaneous mechanical thrombectomy/thrombo-aspiration: what is this?

Answer 21

these are percutaneous techniques that allow for the removal of the thrombus. They can be combined with catheter-directed thrombolysis.

Question 22

Surgical thrombectomy - what is this?

Answer 22

open surgical techniques are still commonly required. One option is surgical thrombectomy in which the vessel is opened and thrombus removed.

Used in acute limb ischaemia if necessary

Question 23

Management of acute limb ischaemia is complex, here is an outline of possible management options…

Answer 23

Initial management: once recognised, if not at a specialist centre, you must liaise with and discuss transfer to your local vascular centre. Initial management typically consists of analgesia and heparin. Heparin is an anticoagulant that potentiates the action of antithrombin III.
Rutherford I: there is generally time to arrange imaging workup (e.g. CTA, DUS). Revascularisation can be attempted with catheter-directed thrombolysis, thrombectomy or bypass.
Rutherford II: urgent revascularisation is indicated and imaging should not delay this. It is typically achieved with a thrombectomy or bypass. If an underlying vascular lesion is present endovascular therapy or surgery should be attempted.
Rutherford III: irreversible damage with dead, non-viable tissue mandates amputation of affected areas.

Question 24

Rutherford I management - Acute PAD

Answer 24

Rutherford I: there is generally time to arrange imaging workup (e.g. CTA, DUS). Revascularisation can be attempted with catheter-directed thrombolysis, thrombectomy or bypass.

Question 25

Rutherford II management - Acute PAD

Answer 25

urgent revascularisation is indicated and imaging should not delay this. It is typically achieved with a thrombectomy or bypass. If an underlying vascular lesion is present endovascular therapy or surgery should be attempted.

Question 26

Rutherford III management - Acute PAD

Answer 26

irreversible damage with dead, non-viable tissue mandates amputation of affected areas.