IB: FEMORAL EMBOLISM Flashcards
What is acute ischaemia often caused by?
Acute ischaemia is most often due to either acute thrombotic occlusion of a previously partially occluded, thrombosed arterial segment, or due to embolus
What happens without surgical revascularisation? Within how long?
Without surgical revascularisation, complete acute ischaemia leads to extensive tissue necrosis within six hours.
What are the effects of sudden artery occlusion?
The effects of sudden arterial occlusion depend on the state of collateral supply. The collateral supply in the leg is usually inadequate unless there has been pre-existing occlusive disease.
The subclavian artery has many collateral vessels so that occlusion of a major artery does not necessarily make a limb nonviable.
What is critical limb ischaemia?
a) what does it suggest?
Critical limb ischaemia is a condition with chronic ischaemic at-rest pain, ulcers, or gangrene in one or both legs, attributable to objectively proven arterial occlusive disease. Critical limb ischaemia implies chronicity and should be distinguished from acute limb ischaemia.
What are the 12 causes? (6 main ones)
- Embolism: for example, left atrium in patients in atrial fibrillation, mural thrombus after myocardial infarction, prosthetic and abnormal heart valves, aneurysm (aorta, femoral, or popliteal), proximal atheromatous stenosis, malignant tumour, or foreign body.
- Thrombosis: most cases of leg ischaemia result from the presence of thrombus at sites of atherosclerotic narrowing; presentation of ischaemia may be:
- Acute, as a result of emboli from rupture of proximal atherosclerotic plaque or thrombus.
- Chronic, usually resulting from gradual extension of thrombus with development of collateral vessels.
- Trauma.
- Raynaud’s syndrome.
- Compartment syndrome: occurs when perfusion pressure falls below tissue pressure in a closed anatomical space; causes include:
- Orthopaedic (tibial or forearm fractures).
- Vascular: haemorrhage, phlegmasia caerulea dolens (massive thrombosis in the major veins of the limbs causing gross swelling that obstructs arterial flow).
- Soft-tissue injury (prolonged limb compression, crush injury, burns).
- Congenital causes of early-onset leg ischaemia, eg aortic hypoplasia.
- Ischaemia of the arm is most often embolism from the heart but may also be due to damage to the subclavian artery or thoracic outlet syndrome.
What are history and exam trying to illicit?
How severe it is
Whether it is embolus or thrombus
What are you looking to ask in history?
rapidity of onset of symptoms, features of pre-existing chronic arterial disease, potential source of embolus and the state of pulses in the contralateral limb.
What are the 6 P’s?
Pale Pulseless Painful Paralysed Paraesthetic Perishingly cold
What does the onset of fixed mottling of the skin imply?
irreversible changes.
What and why might it be misdiagnosed?
The limb may be red when dependent, leading to a misdiagnosis of inflammation, eg gout or cellulitis.
What test might you do? (not bloods)
Hand-held Doppler ultrasound scan may help demonstrate any residual arterial flow.
What blood tests might you do?
FBC (ischaemia is aggravated by anaemia), erythrocyte sedimentation rate (ESR) (inflammatory disease, eg giant cell arteritis, other connective tissue disorders), glucose (diabetes), lipids and thrombophilia screen.
If diagnosis is in doubt what would you do?
perform urgent arteriography.
How could you identify the source of the embolus?
ECG, echocardiogram; ultrasound of the aorta, and the popliteal and femoral arteries.
What is the first thing you would do in acute ischaemia?
Admit the patient - this is an emergency and often requires urgent open surgery or angioplasty.. Immediately heparinise (may double the limb-salvage rate) and provide analgesia.
Ischaemia following trauma and acute thrombosis may require urgent reconstruction.
What would you check for evidence for? (and what would you do about it)
The limb must be checked for evidence of compartment syndrome and, if necessary, a fasciotomy should be performed.
a) What would you do if it is embolic?
b) What would you do if that fails?
c) What is required after successful procedure?
a) If the occlusion is embolic, the options are surgical embolectomy (Fogarty balloon embolectomy catheter) or local intra-arterial thrombolysis.
b) If embolectomy with a Fogarty catheter fails, an on-table angiogram is performed and bypass graft or intraoperative thrombolysis considered. Routine intraoperative angiography for arterial thromboembolectomy has been shown to be beneficial.
c) After successful embolectomy, anticoagulation with heparin is needed to prevent recurrence. Many surgeons postpone heparin for six hours after surgery to reduce the risk of a haematoma.
What would you do for thrombotic disease?
intra-arterial thrombolysis, angioplasty or bypass surgery. If due to thrombosis of an arterial graft, initially attempt thrombolysis.
What do you do for patients with acute arterial emboli or thrombosis?
For patients with acute arterial emboli or thrombosis, treatment with immediate systemic anticoagulation with unfractionated heparin has been recommended. This should be followed by long-term warfarin in patients with embolism.
What other treatment could you suggest?
- Reduction in the rate of deterioration of underlying cardiovascular disease includes regular exercise, smoking cessation, treating hypertension and hyperlipidaemia, and improving diabetes control.
- Management of associated and underlying problems: treat anaemia or polycythaemia, cardiac disease.
- Low-dose aspirin or clopidogrel. Warfarin if otherwise indicated.
- Angiotensin-converting enzyme (ACE) inhibitors have been shown to reduce morbidity and mortality due to cardiovascular disease in patients with peripheral vascular disease by 25%.
- Statins to reduce total and low-density lipoprotein (LDL) cholesterol.
What complications could occur?
- Reperfusion injury may cause more damage than the initial ischaemia:
- Neutrophils migrate into the reperfused tissue, causing injury.
- Limb swelling due to increased capillary permeability may cause a compartment syndrome.
- Leakage from damaged cells may cause acidosis and hyperkalaemia (leading to cardiac arrhythmias) and myoglobinaemia (leading to acute tubular necrosis).
- Chronic pain syndromes: acute complete ischaemia can lead to peripheral nerve injury.
What is the time-limit for acute ischaemia?
6 hours
What is the prognosis?
Complete acute ischaemia will lead to extensive tissue necrosis within six hours unless the limb is surgically revascularised. The mortality associated with acute ischaemia remains high as thrombosis or embolism is not infrequently a pre-terminal event in patients dying from other causes, such as heart failure. Surgical treatment of acute limb ischaemia, because of related complications, has a 30-day mortality rate of 15% to 25%.
Preventative measures
Long-term anticoagulation for potential causes of thromboembolism.
Primary prevention cardiovascular disease; secondary prevention of cardiovascular disease.
