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Gen Surgery > Acute limb ischaemia > Flashcards

Acute limb ischaemia Flashcards

1
Q

What is the definition of acute limb ischaemia

A

ALI is the result of a sudden deterioration in the arterial supply to the limb. A time period of 14 days from the onset of symptoms is utilised to define this clinical entity

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2
Q

What is the aetio-pathology of acute limb ischaemia (the broad approach

A
  • Embolism: cardio-embolism and arterio-embolism
  • Thrombosis: Vascular graft thrombosis, in-stent thrombosis, native artery thrombosis, peripheral aneurysms
  • Trauma: Blunt and penetrating
  • Iatrogenic injury: post-catheterisation, following lower extremity surgery
  • Malperfusion: Aortic dissection, isolated peripheral arterial dissection
  • Thrombophilia: unexplained graft occlusion, occlusion of normal native arteries
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3
Q

what is an embolism?

A

It is the result of material passing through the arterial tree and obstructing a peripheral artery.

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4
Q

Where do emboli usually lodge

A
  • They lodge peripherally, usually at an arterial bifurcation, where vessels naturally narrow.
  • Emboli can occlude any artery but in the legs, the common femoral and popliteal arteries are commonly obstructed.
  • Only large emboli, such as saddle emboli occlude the normal aortic bifurcation
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5
Q

What are the causes of cardiac embolism

A
  • Atrial and ventricular
  • Paradoxical
  • Endocarditis
  • Cardiac tumour
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6
Q

What is the cause of atrial and ventricular cardiac embolism?

A
  • The most common cause is atrial fibrillation (thrombus forms in the left appendage)
  • Mural thrombus as a result of acute myocardial injury due to infarctionn
  • Left ventricular aneurysm
  • Cardiac valve disease (very rare)
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7
Q

What is a paradoxical embolism

A

Paradoxical embolism occurs when a clot from the venous system, usually a deep venous thrombosis travels through a patent foramen ovale into the arterial system. The clinical clue is acute limb ischaemia in a patient with known DVT

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8
Q

Which patients are at risk for an embolism due to endocarditis

A
  • Iv drug abusers
  • Patients with indwelling arterial or venous lines
  • Immunocompromised patients
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9
Q

Which cardiac tumor causes acute limb ischaemia?

A

Atrial myxoma is a beneign tumour of the left atrium that may fragment as it enlarges

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10
Q

What are the causes of arterial embolism

A
  • Atheroembolism

- Aortic mural thrombi

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11
Q

What is usually the underlying cause of aortic mural thrombi

A

-Patients with hypercoaguable conditions develop an aortic mural thrombus in the absence of aortic pathology, which then embolises to the limb

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12
Q

What is the cause of thrombosis within an artery?

A
  • progressive atherosclerotic obstruction
  • hypercoagulability
  • arterial dissection

It is caused by blood clotting within an artery

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13
Q

Why is an atherosclerotic obstruction less dramatic than an embolus?

A

Progressive process of atherosclerotic narrowing results in the development of robust collateral circulation. The symptoms of ischemia improve as collaterals expand. Critical ischaemia is the end result when the process occurs at multiple levels

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14
Q

How does aortic dissection present

A
  • it presents as iliac artery thrombosis
  • these patients have back pain and be hypotensive
  • renal failure if the dissection involves the renal arteries
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15
Q

Isolated arterial dissections of the lower limb are caused by what?

A

These are rare but can occur from traumatic or fibrodysplastic causes

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16
Q

Is bypass graft occlusion more likely to be due to embolism or thrombosis?

A

Thrombosis

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17
Q

In severe ischaemia, when does irreversible muscle necrosis occur?

A

6-8 hours

This is why it’s important to ask for the duration of symptoms

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18
Q

What symptoms indicate the need for urgent intervention

A

Acute white leg
Sensory loss
Muscle pain

This is evidence of critical ischaemia

19
Q

What history for patients with acute on chronic thrombosis usually give

A

Prior intermittent claudication in the ipsilateral or contralateral leg

20
Q

What does slow capillary refill indicate

A

This is a sign that at least a small degree of distal flow is present and runoff vessels are probably patent

21
Q

Which modalities of sensation should be tested for specifically

A

Fine touch and proprioception

22
Q

Acute ischaemia is associated with loss of peripheral pulses. What do palpable normal pulses in the contralateral leg point towards

A

Points towards embolism as the cause

23
Q

How may a strong pulse mask an occlusion at that level

A

The water hammer effect

24
Q

On handheld Doppler exam, what do soft monophasic signals indicate

A

Soft, monophasic signals are associated with patent distal vessels but proximal arterial occlusion

25
Q

In severe ischamia, ankle pressures are impossible to measure, what do you expect in less severe ischaemia

A

Ankle pressure of 30- 50 mmHg

Ankle brachial index of about 0.3 is diagnostic of subcritical acute ischaemia

26
Q

What is the classification of acute limb ischaemia

A 
I. viable 
II. Threatened 
IIa. Marginally threatened 
IIb. immediately threatened 
III. irreversible
27
Q

What are the characteristics of class IIa and IIb in the classification of acute limb ischaemia

A
  • IIa (acute subcritical ischaemia): minimal sensory loss (toes), no muscle weakness, inaudible arterial pulse, audible venous pulsation.
  • IIb (Acute critical ischaemia): sensory loss more than toes, severe rest pain, mild/moderate muscle weakness, inaudible arterial pulse, audible venous pulsation
28
Q

How does aortic occlusion present

A
  • Paralysis of legs
  • Mottled skin discolouration that often extends above the inguinal ligament onto the lower abdomen
  • No palpable extremity pulses
  • if involves renal arteries –> renal failure
29
Q

How does iliac occlusion present

A
  • findings similar to aortic occlusion, but unilateral
  • Femoral pulse lost on affected side
  • Mottling usually extends to the inguinal level
  • Aortic dissection should be excluded
30
Q

What is the most important thing determining the severity in a femoropopliteal occlusion

A
  • Whether the profunda femoris remains patent.

- The symptoms are more severe if the profunda is involved.

31
Q

What are causes of popliteal and infrapopliteal occlusion

A
  • In young patients rare diagnoses include popliteal thrombosis due to muscular entrapment or cystic adventitial disease
  • The most sinister cause is popliteal aneurysm thrombosis or embolisation (suspected if generous popliteal pulse is palpated in either leg or there is a nonpulsatile mass in the poplliteal fossa of the affected leg
32
Q

What information can a transfemoral arteriography give you? and when should it be done

A

The angiogram can document the level of the occlusion and sometimes its nature.
The best reason to perform angiography is when an endovascular solution to the arterial occlusion is likely

33
Q

What information can duplex doppler give you

A
  • Define level of arterial occlusion

- Patency of other vessels

34
Q

When should CTA be done

A

aorto-iliac occlusions

35
Q

When is echocardiography indicated

A
  • Young patients
  • Cardiac diagnosis is suspected
  • Those in whom results might affect decisions about long term anti-coagulation
36
Q

What are the steps in inital management of patients with acute limb ischaemia?

A
  • Anti-coagulation: initial bolus of 5000 U of IV calcium heparin followed by IV infusion commencing at 1000 U/ hr. Aim for Partial thromboplastin time of 2-3
  • Facemask oxygen
  • Intravenous fluid
  • Catheter to monitor output
  • U and E, FBC
  • Recurrent thrombosis: thrombophilia screen indicated
  • Analgesia: patient controlled intravenous analgesia
37
Q

What are the options for definitive treatment of acute limb ischaemia?

A
  • Anticoagulation alone
  • Operative intervention
  • Endovascular intervention via mechanical thrombectomy or thrombolysis
38
Q

When is anticoagulation alone usually done for acute limb ischaemia?

A
  • Limb likely to remain viable
  • other therapeutic options limited
  • Stable class I ischaemia treated with anticoagulation followed several weeks later by intervention (usually endovascular) if collaterals do not become established
  • Class III irreversible ischaemia, anticoagulation allows stabilization of the patient while his/ her medical condition is improved pending major amputation at a later date.
39
Q

Which class of patients need urgent intervention

A

From Class IIb

40
Q

What are the options for treatment of acute critical ischaemia

A
  • Percutaneous thrombectomy or ACCELERATED thrombolysis if expertise available
  • Operative interventions: embolectomy, reconstruction, on-table angioplasty or thrombolysis
41
Q

what are the treatment options for patients with acute subcritical ischaemia?

A
  • Obvious emboli-> embolectomy
  • Intra-arterial thrombolysis with or without adjunctive mechanical thrombectomy
  • Surgical options best in a fit patient
  • Thrombolysis in particular is indicated when the surgical options are poor and the runoff vessels in the leg appear occluded
  • Thrombolysis is best for short duration ischaemia and bypass graft occlusions.
42
Q

What are the most common sites for arm emboli?

A

-Brachial artery followed by axillary artery

43
Q

How can outcome of a patient with acute limb ischaemia be predicted

A

-Pre treatment POSSUM physiology scores

Gen Surgery (31 decks)

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