Acute Limb Ischaemia

Question 1

Major causes of acute limb ischaemia?

Answer 1

• Arterial embolism
• Thrombosis
• Trauma
• Iatrogenic

Question 2

What is an embolism?

Answer 2

When material passes through the arterial tree and obstructs an artery

Question 3

Two main causes/sources of embolism?

Answer 3

• Mural thromboembolism from the heart

- Atherosclerotic debris from a diseased proximal artery, often the thoracic aorta

Question 4

Clinical features of embolism

Answer 4

• Acutely white limb
• Complete neuroses sorry defect
• No established collaterals so ischaemia can be catastrophic
• occlusion can be progressive with secondary thrombus formation and distal embolisation

Question 5

Different types of embolism/causes

Answer 5

Atrial/ventricular: thromboembolism following atrial fibrillation; mural thrombus due to acute MI; left ventricular aneurysm due to low CO
Paradoxical: DVT embolising to arterial system through patent foremen ovale
Endocarditis
Cardiac tumour e.g. Atrial myxoma
Atheroembolism
Aortic mural thrombi: hypercoagulable patients without aortic disease

Question 6

Definition of thrombosis

Answer 6

Blood clotting within an artery, caused by either atherosclerotic obstruction, hyper-coagulability or arterial dissection

Question 7

Mechanism of atherosclerotic obstruction?

Answer 7

Progressive atherosclerotic narrowing of the arterial lumen, followed by platelet thrombus formation on the stenosis lesion, causing acute arterial occlusion
Progressive process -> step-wise (collateral vessels) -> can be precipitated by low CO states e.g. Hypovolaemia

Question 8

Definition of acute limb ischemia

Answer 8

Sudden deterioration of the arterial supply of a limb, within 14 days of onset of symptoms

Question 9

Mechanism of hyper-coagulable states

Answer 9

Hyper-coagulability, low arterial flow, hyper-viscosity

Thrombocythaemia in particular can cause arterial occlusion (usually small vessels)

Question 10

In the setting of severe ischaemia, how long does it take for severe muscle necrosis to occur?

Answer 10

6-8 hours

Question 11

NB risk factors for atherosclerotic disease

Answer 11

Smoking
Hypertension
High cholesterol
Family history

Question 12

General intervention for Class I acute limb ischaemia?

Answer 12

Conservative management, because the limb isn’t yet threatened, and the risks of the therapy, particularly thrombolysis outweigh the benefits

Question 13

General intervention for Class III acute limb ischaemia?

Answer 13

Decision is between major amputation and conservative treatment: no benefit in reperfusing limb as the ischaemia is already irreversible, and may cause a reperfusion kidney injury

Question 14

What are the clinical and Doppler findings in Class I acute limb ischaemia?

Answer 14

Class I = viable
Sensory loss: none
Muscle weakness: none
Arterial Doppler: audible
Venous Doppler: audible

Question 15

What are the clinical and Doppler findings in Class IIa acute limb ischaemia?

Answer 15

Class IIa = marginally threatened
Sensory loss: Minimal (toes)
Muscle weakness: None
Arterial Doppler: Inaudible
Venous Doppler: Audible

Question 16

What are the clinical and Doppler findings in Class IIb acute limb ischaemia?

Answer 16

Class IIb = immediately threatened
Sensory loss: >toes; severe rest pain
Muscle weakness: mild/moderate
Arterial Doppler: inaudible
Venous Doppler: audible

Question 17

What are the clinical and Doppler findings in Class III acute limb ischaemia?

Answer 17

Class III = irreversible ischaemia
Sensory loss: profound/anaesthetic
Muscle weakness: profound/paralysis
Arterial Doppler: inaudible
Venous Doppler: inaudible

Question 18

What is the major clinical difference between Class IIa and IIb acute limb ischaemia?

Answer 18

IIa = subcritical
IIb = critical
3 findings that best differentiate: pain at rest, sensory loss, muscle weakness

Question 19

Initial management of acute limb ischaemia?

Answer 19

• Anticoagulation: unfractionated heparin 5000U initial bolus, then 1000U/hour –> aim for PTT ~2-3
• Facemask O2
• IV fluids
• Urine output monitoring
• Blood screening tests: FBC, U&E, creatinine
• Analgesia (IM opiates contraindicated because of thrombolysis - give IV)

Question 20

What is the benefit of heparin in managing acute limb ischaemia?

Answer 20

Isn’t thrombolytic - stabilises clot to prevent secondary thrombosis