acute limb ischaemia

Question 1

how does acute limb ischaemia differ from critical limb ischaemia?

Answer 1

ALI presents ‘acutely’, in comparison to critical limb ischaemia which carries a progressive course over a period of > 2 weeks.

Question 2

what are the main causes of acute limb ischaemia?

Answer 2

1. embolus
   - AF
   - MI
   valvular vegetations
2. thrombus
   occurs when an atheromatous plaque in an artery ruptures and a thrombus forms on the plaque’s cap. Peripheral vascular disease is the underlying cause of thrombosis.

Question 3

where is the most common site for embolisation?

Answer 3

femoral artery

Question 4

where are the first areas to get damaged in acute limb ischaemia?

Answer 4

Nerves are the first to be affected, with irreversible damage after 6 hours. Muscles are more tolerant, with irreversible damage after 6-10 hours, whilst the skin is the last to show necrosis.

Question 5

what are the symptoms of an acute limb ischaemia?

Answer 5

• pain
• pallor
• pulseless
• paresthesia
• perishingly cold
• paralysis

Question 6

what are key differences in the history and examination of an embolic event vs ischaemic event?

Answer 6

• embolic is sudden but thrombotic is progressive
• embolic may be caused by a cardiac event but thrombotic is not
• embolic usually doesn’t have a history of PAD but thrombotic does
• embolic will have normal contralateral limb but thrombotic will not
• embolic will have a clear demarcation but thrombotic will not

Question 7

what is the golden rule for acute limb ischaemia?

Answer 7

The golden rule is not to delay surgical intervention by performing investigations if there is a strong clinical suspicion of limb-threatening ischaemia.

Question 8

why would you do Uand E when investigating acute limb ischaemia?

Answer 8

electrolyte disturbance may be associated with an underlying arrhythmi

Question 9

why would measuring CK be indicated in acute limb ischaemia?

Answer 9

elevated if rhabdomyolysis has taken place

Question 10

what is the name of the classification system used in acute limb ischaemia?

Answer 10

rutherford classification

Question 11

what are the features of a cat 1 rutherford ischaemic limb?

Answer 11

it is viable
sensory: present
motor: present
arterial doppler: present

Question 12

what is the difference between at type 2a vs type 2b rutherford acute limb?

Answer 12

both are threatened limbs
sesnory: there is partial loss in both, but in type a its limited to just toes, type b is beyond toes

motor: present in type a, but partial loss in type b
doppler: flow is absent in both

Question 13

what are the features of a type 3 rutherford acute limb ischaemia?

Answer 13

• it is an irreversible ischaemia
  sensory: profound loss
  motor: profound paralysis
  doppler: absent flow

Question 14

what is the initial managemnt for acute limb ischaemia?

Answer 14

IV unfractionated heparin (UFH): UFH has a shorter half-life than low-molecular-weight heparin (LMWH), making it an effective, more reversible pre-operative anticoagulant

Question 15

what is the definitive management for a rutherford type 3 acute limb ischaemia?

Answer 15

Amputation
Palliation

Revascularisation will likely kill the patient due to the extensive release of radical oxygen species and other metabolites.

Question 16

what are the definitive treatment management options for a rutherford type 1-2a ischaemia?

Answer 16

I (viable): revascularise within 6-24 hours
Catheter-directed thrombolysis or thrombectomy

IIA (threatened): revascularise within 6 hours
Catheter-directed thrombolysis or percutaneous thromboembolectomy

IIB (threatened): revascularise within 6 hours
Percutaneous or open thromboembolectomy
Bypass surgery is now less commonly performed

Question 17

what are long term management options of PAD?

Answer 17

educe cardiovascular risk: smoking cessation, a supervised exercise programme, dietary modifications and managing cardiovascular comorbidities

Antiplatelet therapy: clopidogrel is preferred in peripheral arterial disease as it reduces cardiovascular event rates in patients with claudication

Statin: atorvastatin 80mg

Question 18

what are complicatons of limb ischaemia?

Answer 18

Gangrene: occurs in the non-viable leg and usually requires amputation (Rutherford III)

Rhabdomyolysis: due to the death of muscle fibres and release of their contents into the bloodstream, potentially resulting in acute renal failure and arrhythmias

Ischaemia-reperfusion injury: reperfusion of the ischaemic limb can release reactive oxygen radicals and inflammatory mediators, resulting in swelling and muscle ischaemia. Damaged muscle cells release toxic metabolites, resulting in arrhythmias and acute kidney injury

Permanent limb pain/weakness

Question 19

which arterial examination should be performed when suspecting acute limb ischaemia?

Answer 19

hand held doppler