acute limb ischaemia

Question 1

what is acute limb ischaemia?

Answer 1

the sudden decrease in limb perfusion that threatens the viability of the limb

complete or even partial occlusion of the arterial supply of a limb can lead to rapid ischaemia and poor functional outcomes within hours

Question 2

what are the causes of acute limb ischaemia?

Answer 2

• embolisation e.g from sites as a result of AF, post MI mural thrombus, AAA or prosthetic heart valves
• thrombus in situ where atheroma ruptures in artery and thrombus forms on plaques cap (can present as acute or acute on chronic)
• trauma, less common. includes compartment syndrome

Question 3

what are the signs and symptoms of acute limb ischaemia?

Answer 3

6 P’s

• pain
• pallor
• pulselessness
• paraesthesia
• perishing cold
• paralysis

top 3 are the most common initial features.

• sudden onset
• normal contralateral limb suggests embolic occlusion
• causes of potential embolisation should be considered

Question 4

what are the differentials for acute limb ischaemia?

Answer 4

critical chronic limb ischaemia

acute DVT

spinal cord or peripheral nerve compression

Question 5

what investigations should be done into acute limb ischaemia?

Answer 5

• routine bloods including serum lactate to asses ischaemia level
• thrombophilia screen if <50 without known risk factors
• asses with bedside doppler USS of both limbs, followed by CT angiography
• if limb is salvageable, CT arteriography can provide more info on the anatomical location of the occlusion and help with surgical approach

Question 6

how is an acute ischaemic limb initially managed?

Answer 6

surgical emergency
can get irreversible tissue damage within 6 hours

start on

• high flow oxygen
• IV access
• therapeutic heparin dose or bolus dose, then heparin infusion

Question 7

how is acute limb ischaemia managed conservatively?

Answer 7

can consider with those with no or minimal sensory loss and audible arterial and/or venous doppler

• prolonged corse of heparin
• asses regularly
• APTT (activated partial thromboplastin time) test should be done with clinical reviews

Question 8

what surgical intervention options are there for embolic causes of acute limb ischaemia?

Answer 8

• embolectomy via Fogarty catheter
• local intra arterial thrombolysis
• bypass surgery if there is insufficient flow back

NB: Most post-operative cases require a high level of care, typically at a high dependency unit, due to the ischaemia reperfusion syndrome.

Question 9

what surgical intervention options are there for thrombotic causes of acute limb ischaemia?

Answer 9

• local intra arterial thrombolysis
• angioplasty
• bypass surgery

NB: Most post-operative cases require a high level of care, typically at a high dependency unit, due to the ischaemia reperfusion syndrome.

Question 10

when will a limb need amputation and what aftercare is needed?

Answer 10

when there is irreversible limb ischaemia

(mottled, non blanching appearance with hard woody muscles)

after, need

• occupational therapy
• physiotherapy
• long term rehabilitation plan

Question 11

how is acute limb ischaemia managed in the long term?

Answer 11

• reduce CV mortality risk by lifestyle changes
• start on anti platelet agent egg aspirin/clopidogrel, or even anticoagulation with warfarin or DOAC
• treat underlying conditions

Question 12

what is reperfusion injury?

Answer 12

a complication of acute limb ischaemia

sudden increase in capillary permeability can result in

• compartment syndrome
• release of substances from damaged muscle cells e.g

K ions = hyperkalaemia
H ions = acidosis
Myoglobin = AKI

need to monitor patients at risk of compartment syndrome carefully and treat rapidly

electrolyte imbalance due to RI requires close monitoring and potential haemofiltration