Limb Ischaemia

Question 1

Define acute limb ischaemia.

Answer 1

Acute limb ischaemia is defined as a sudden decrease in limb perfusion that causes a potential threat to limb viability.

Question 2

What are the causes of acute limb ischaemia?

Answer 2

• Embolus - most common cause.
  
  • When material from somewhere more proximal lodges in a blood vessel and causes a sudden occlusion.
• Thrombosis - 2^nd most common cause.
• Trauma
  
  • E.g. femoral fracture (may have injury to superficial femoral artery). ALWAYS check circulation in a trauma situation. ?pulses.
• Dissection
  
  • Haemorrhage in the media of the vessel wall.

Question 3

Describe the pathophysiology of how an embolus causes acute limb ischaemia.

Answer 3

• Often a cardiac source.
  
  • AF - ventricles not emptying properly and thrombus can form.
  • Valvular heart disease - valve replacement that are not adequately anticoagulated.
  • Mural thrombus - develops on the wall of the ventricle. Post MI, often raw area of ventricular muscle which is pro-thrombotic. Thrombus can form on this wall and it can embolise and cause ischaemia.
  • Endocarditis - can have vegetations attached to the wall of the heart. These infected vegetations can break off and travel around the body. Can cause ischaemic limbs or strokes. Can als end up with septic emboli which means you are also dealing with infection. Can cause vessel wall to break down.
  • Atrial myxoma - RARE.
• Aortic and peripheral artery aneurysms - as an arterial wall dilates up to form an aneurysm, the blood flow is turbulent and thrombus formation around the walls of the aneurysm.
• Atherosclerotic plaque with plaque rupture - can rupture and expose the endothelium of the vessel wall – very pro-thombotic. Thrombus forms on the top of this; this is very unstable and can easily break off and lodge in a more distal vessel, causing an acute episode of ischaemia.

Question 4

Describe the pathophysiology of how thrombosis can cause acute limb ischaemia.

Answer 4

• Plaque rupture and occlusion of pre-existing stenosis.
• Usually background of claudication / PVD - more complicated pattern of disease. There is collateral angiogenesis
• Causes a sudden deterioration of the symptoms.

Question 5

Describe the typical presentation of an acutely ischaemic limb.

Answer 5

• Elderly patient
• Often new AF, or AF without adequate anticoagulation.
• Signs:
  
  • Pallor
  • Pain
  • Polar (cold) - early sign
  • Pulseless - early sign
  • Paraesthesia
  • Paralysis - late sign
• However:
  
  • Progressive signs - may be irreversible muscle damage by 6 hours.
  • Pre-existing PVD or thrombosis in situ will modify presentation.

Question 6

Describe how to assess a patient with ?acute ischaemic limb.

Answer 6

• History (risk factors).
• Pulses (+ contralateral).
• Capillary refill / veins.
• Sensation.
• Motor function.
• Squeeze calf - calf tenderness.
• Ask to wiggle toes on BOTH feet. They may be able to move toes on ischaemic side, but if bilaterally, it is not the same, THIS IS ABNORMAL.
• Sensorimotor deficit requires prompt intervention.
• Fixed mottling and paralysis are irreversible changes.
• Fixed (unblanching) mottling and paralysis = irreversible change.
• If they have a thrombus in one leg, they may have thrown a clot down the other leg too. So, while 1 leg is acutely ischaemic, the other may be a little ischaemic too. If the contralateral leg is completely normal, this makes embolus a much more likely cause of ischaemia in the symptomatic leg.

Question 7

What should you consider once you have treated and blood has rushed back into the ischaemic limb?

Answer 7

• Consider fasciotomy because the patient is at risk of compartment syndrome.
• Releasing the fascia surrounding the muscles to allow them to swell.

Question 8

How would you manage a patient with an acutely ischaemic limb?

Answer 8

• Analgesia - often opioid required.
  
  • Sometimes necessary before you can assess px.
• Hydration - very high risk of renal failure. As ischaemia develops, there is breakdown of muscle so high levels of CK and myoglobin and myolobinuria (rhabdomyolysis) so be KIDNEY CAREFUL.
  
  • It is a fine balance between renal protection and fluid overload and the risk of heart failure so catheterise to monitor UO and hang fluids.
• LMWH or IV UF heparin.
  
  • This is not to dissolve clot, but rather to stop it propagating further.
• Imaging (if required).
• Intervention.

Question 9

Describe endovascular repair of acute limb ischaemia.

Answer 9

• Good option if this is an acute problem ont op of a background chronic condition.
• Takes time to organise - class 1 or 2a acute ischaemia.
• Thrombolysis and angioplasty or stent.
• Risk of distal embolisation.

Question 10

Under what circumstances would a fem-pop / fem-distal bypass be appropriate?

Answer 10

• Acute thrombosis on a background of chronic disease.
• Suitable if more extensive pattern of disease.

Question 11

Why should you investigate the cause of embolus even after limb ischaemia has been treated?

Answer 11

• The embolus has come from somewhere.
• INVESTIGATE THIS.
• Unless you do this and anticoagulate if necessary, the patient is at risk of further emboli and stroke.

Question 12

Define chronic limb ischaemia.

Answer 12

• Decrease in limb perfusion which may or may not threaten the viability of the limb of duration > 2 weeks.

Question 13

What is the cause of chronic limb ischaemia?

Answer 13

• Due to atherosclerosis.
  
  • Build up of lipid, calcium and fibrous tissue within the intima of the arterial wall.
  • Once >50% of th arterial cross-sectional diameter is occupied with atheromatous plaque, this becomes flow limiting and may lead to symptoms.
  • Fibrous plaque is vulnerable to rupture - if the endothelium is exposed, thrombosis may cause an acute deterioration in symptoms due to sudden narrowing of the lumen.

Question 14

Describe peripheral arterial disease.

Answer 14

• Progressive disorder charaterised by stenosis or occlusion of large and medium sized arteries (other than coronary or cerebral arteries).
• 10-20% of patients >60 have PAD.
• Over half are aymptomatic.
• Increased risk of CV mortality (~5% risk of mortality, MI or stroke per year).
• Underdiagnosed and undertreated.

Question 15

What are the risk factors for peripheral arterial disease?

Answer 15

• Smoking
• Age
• Male
• Hypertension
• Hyperlipidaemia
• Diabetes
• Ethnicity
  
  • Less common in Chinese than Caucasians, more common in African Americans.

Question 16

Describe intermittent claudication.

Answer 16

• Pain or tightness, often in calves, on walking.
  
  • Muscle group that is painful will be that supplied by narrowed artery.
• Usually occurs after the same distance on the flat, but worse on hills.
• Eases after resting for 1-2 minutes.
• How do patients most commonly present with PAD?
  
  • Pain on walking or exercising – initially, collaterals supply the muscle group, but as metabolic demand increases the blood supply needs to increase to allow aerobic respiration. Unhealthy vessels can’t vasodilate to do this so anaerobic resp/ lactic acid/ pain. Rest.

Question 17

What is the most common differential diagnosis when considering peripheral arterial disease in a patient presenting with ?intermittent claudication?

Answer 17

• Most common DDx is spinal stenosis.
  
  • This occurs due to narrowing of the spinal canal and also causes calf pain on walking.
  • A good history can differentiate them – spinal stenosis has good days and bad, takes a lot longer to resolve on resting (around 10-20 mins), is much more easily eased by sitting, and also occurs on standing still.

Question 18

Describe how to examine a patient with ?peripheral arterial disease.

Answer 18

• Inspection
  
  • Scars (remember groins)
  • Ulceration (between toes and on heel)
  • Colour - any pallor?
  • Venous guttering
• Palpation
  
  • Temperature
  • Cap refill time
  • Pulses - start with dorsalis pedis and posterior tibial pulse and work proximally.
  • The aortic pulse is the most proximal of the lower limb pulses.

Question 19

What is venous guttering?

Answer 19

Venous guttering occurs when the leg is elevated. If arterial inflow is satisfactory the veins should still fill despite elevation. If they empty and you can see shallow “gutters” where the veins have been, this indicates a fairly ischaemic limb.

Question 20

Describe how ABPI can be useful in assessing patients with ?peripheral arterial disease.

Answer 20

• ABPI = ratio of the ankle to the brachial occlusion pressure.
• Normal = 0.8-1.2.
• Low ABPI is usually due to calcified vessels - not reliable in diabetics due to widespread calcification of arteries.
• In isolation, asymptomatic ABPI outwith normal range does not merit treatment or referral.

Question 21

What investigations can be used to assess peripheral arterial disease?

Answer 21

• Duplex USS
• MR angiography
• CT angiography

Question 22

How are patients with peripheral arterial disease managed?

Answer 22

• Aggressive management of risk factors
  
  • Smoking cessation
  • Hypertension control
  • Good control of diabetes
• Medications
  
  • Aspirin or clopidogrel
  • Statin
• Supervised exercise
• Reassure - a very small % deteriorate to limb-threatening ischaemia.

Question 23

Which patients should be referred?

Answer 23

• Patients who are likely to benefit from intervention:
  
  • Short distance claudicants (<100m)
  • Sudden onset of symptoms
  • Lifestyle-limiting
  • Threatening employment
  • Rapidly deteriorating
  • Especially if all risk factors are addressed
• Uncertain diagnosis

Question 24

Describe the presentation of chronic limb ischaemia.

Answer 24

• Chronic (<2 weeks) ischaemic rest pain, necrosis or ulceration, as a result of proven arterial disease.
• Gangrene, ulcers non-healing wounds.
• May have background of claudication.
• Many patients present with CLTI as first presentation of PAD.
• Careful history and examination as before.

Question 25

Describe the initial management of chronic limb ischaemia.

Answer 25

• Risk factors
  
  • Aggressive urgent management
• Analgesia
  
  • Patients will often need opiate analgesia
• Remember neuropathic pain
  
  • Consider gabapentin or pregabalin

Question 26

When should a patient with chronic limb ischaemia be referred?

Answer 26

• Refer early, rather than urgently.
• If in doubt, phone the on call vascular team.
• Urgent referral for inpatient treatment:
  
  • Extensive tissue loss
  • Sepsis associated with necrosis or ulceration
  • Uncontrollable pain
• Podiatry can be very useful to help with wounds - in addition to referral to vascular surgery rather than instead of.

Question 27

How is chronic limb ischaemia managed?

Answer 27

• Aim is to revascularise the limb.
• Depending on where the disease is, the revascularisation may be relatively straightforward, or it may be extensive, complex and high risk.
• Claudication - revascularisation aims to increase quality of life.
• Chronic limb threatening ischaemia - revascularisation aims to prevent limb loss.

Question 28

What are the options for management of chronic limb ischaemia?

Answer 28

• Primary amputation - in ~15% of patients with CLTI.
• Conservative treatment - ~20%.
• Revascularisation - ~65%.
• Open surgery (endarterectomy or bypass of blockages).
• Endovascular (angioplasty or stenting).
• Combination of the two (hybrid or combined procedures).

Question 29

Describe the endovascular treatment of chronic limb ischaemia.

Answer 29

• Angiography allows accurate diagnostic imaging, and if appropriate, direct progression to angioplasty or stent.
• Direct arterial pressure, with introduction of a sheath, and then injection of iodinated contrast to opacify vessels.
• Stenoses or occlusions identified and can be crossed with a wire and balloon, and opened up and / or stented.
• Carried out by direct puncture of the artery (often femoral) under local anaesthetic.

Question 30

Describe open surgical revascularisation.

Answer 30

• Usually surgical bypass.
• Uses conduit such as native vein (GSV) or prosthetic graft or biological graft to bypass occluded segments of artery.
• Requires good ‘inflow’, good conduit and good ‘runoff’ to maintain graft patency.
• Frequently combined with endovascular procedures to achieve this result.

Question 31

What are the pros and cons of endovascular treatment for CLTI?

Answer 31

• Lower morbidity and mortality.
• Lower longterm patency rates.
• Main immediate complications:
  
  • Groin puncture (pseudoaneurysm or bleeding)
  • Thrombosis
  • Dissection
  • Embolus
• Long-term complications:
  
  • Stent stenosis
  • Thrombosis

Question 32

What are the pros and cons of the open approach to treating CLTI?

Answer 32

• Difficult operation in comorbid population - specialist anaesthetic team.
• Higher immediate morbidity and mortality.
• Higher long-term patency rates.
• Common coplications:
  
  • Infection
  • Bleeding
  • MI
  • Graft failure
  • Nerve damage
• Long-term complications:
  
  • Graft thrombosis

Question 33

Which patients should be treated using endovascular technique and which with open technique?

Answer 33

• Endovascular approach best suited to stenoses or short occlusions, or less fit patients with lower life expectancy, open approach suitable for longer occlusions or multilevel disease, or fitter patients.
• Basil – in patients with disease that could be treated by either endovascular or open intervention, open surgery was recommended in those likely to survive > 2 years, and endovascular < 2 years.

Question 34

Describe the different types of amputation and state when a patient should be offered this.

Why are amputations carried out?

Answer 34

• Can be minor amputation (confined to foot) or major )more proximal).
• Minor amputations are often combined with revascularisation in order to achieve healing of the wound.
• Major limb amputations may be primary or secondary.
• Level of amputation depends on vascularity, skin and tissue, and current and future mobility of the patient.
• Generally the more distal, the better function.
• Amputations are carried out either because there is no option for revascularisation, or revascularisation has failed, and patient cannot live with limb.