Acute Limb ischaemia

Question 1

Define acute limb ischaemia

Answer 1

Sudden decrease in limb perfusion that threatens the viability of the limb. It is a surgical emergency

Question 2

Aetiology of acute limb ischaemia

Answer 2

Occlusion of the arterial supply → rapid ischaemia and poor functional outcomes

1. Embolisation whereby a thrombus from a proximal source travels distally to occlude the artery (most common)
   a. AF
   b. Post-MI mural-thrombus
   c. Abdominal aortic aneurysm
   d. Prosthetic heart valves
2. Thrombosis in situ whereby an atheroma plaque in the artery ruptures and a thrombus forms on the plaque’s cap (presenting as acute or acute-on-chronic)
3. Trauma (less common), including compartment syndrome

Question 3

Classification of acute limb ischaemia

Answer 3

Viable: no sensory/motor deficit, arterial and venous doppler both audible

IIa: minimal sensory loss, inaudible arterial doppler

IIb: sensory loss, mild motor deficit, inaudible arterial doppler

III: profound sensory/motor deficits, inaudible arterial AND venous doppler

Question 4

Symptoms of acute limb ischaemia

Answer 4

Pain
Pallor
Pulselessness
Paresthesia
Perishingly cold
Paralysis

Question 5

What suggests that acute limb ischaemia has been caused by thrombus

Answer 5

pre-existing claudication with sudden deterioration
no obvious source for emboli
reduced or absent pulses in contralateral limb
evidence of widespread vascular disease (e.g. myocardial infarction, stroke, TIA, previous vascular surgery)

Question 6

What suggests acute limb ischaemia has been caused by embolus

Answer 6

sudden onset of painful leg (< 24 hour)
no history of claudication
clinically obvious source of embolus (e.g. atrial fibrillation, recent myocardial infarction)
no evidence of peripheral vascular disease (normal pulses in contralateral limb)
evidence of proximal aneurysm (e.g. abdominal or popliteal)

Question 7

Investigations for acute limb ischaemia

Answer 7

ECG

VBG
FBC
U&Es
LFTs
CRP
Thrombophilia screen
G&S

Doppler US: if present → ABPI
CT angiography
CT arteriogram

Question 8

Management for acute limb ischaemia

Answer 8

A-E + senior support
High-flow oxygen + IV access
Therapeutic dose heparin/IV heparin infusion should be initiated as soon as is practical.

Conservative (rutherford 1 and 2a) → prolonged heparin, regular APTT

Embolus
Surgical (Rutherford 2b etc.) → embelectomy via fogarty catheter → intra-arterial thrombolysis
Bypass surgery (if there is insufficient flow back), or to exclude an occluded popliteal aneurysm

Thrombosis
Local intra-arterial thrombolysis
Angioplasty, likely combined with thrombolysis
Bypass surgery

Question 9

Long-term management after acute limb ischaemia

Answer 9

Reducing CVD risk: Regular exercise, smoking cessation, and weight loss as necessary.
Anti-platelet agent e.g. low-dose aspirin or clopidogrel OR anticoagulation with warfarin or a DOAC.
Treat any underlying predisposing conditions e.g. uncontrolled atrial fibrillation.
Cases resulting in amputation will require occupational therapy and physiotherapy, with a long term rehabilitation plan discussed and transfer to an intermediate rehabilitation centre.

Question 10

Complications of acute limb ischaemia

Answer 10

Reperfusion injury: sudden increase in capillary permeability can result in:
- Compartment syndrome
- Hyperkalaemia
- Acidosis
- AKI from myoglobin release

Question 11

Prognosis for acute limb ischaemia

Answer 11

Mortality rate 20%