Acute Limb Ischaemia Flashcards
Define embolism?
-mass of material traveling through blood vessels and lodging at bifurcations
Define thrombosis?
-formation of blood clot in situ
What are the sources of embolism?
- Cardiac 80-90%
- Arterial
- Iatrogenic from coils
Define acute limb ischaemia?
- sudden decrease in limb perfusion that poses a risk to limb viability
- usually less than 2 weeks
Where are the common sites where emboli lodge?
- Femoral artery bifurcation- 36%
- Popliteal artery trifurcation- 15%
- Aortic trifurcation-22%
- External and internal iliac arteries-22%
- Arm-14%
What are the causes of cardiac emboli?
- atrial fibrillation-70%
- myocardial infarction with left ventricular mural thrombosis-20%
- mechanical valves
- endocarditis
- ventricular aneurysm
What are the causes of arterial emboli?
- artherosclerosis
- mural thrombosis from aneurysm
What is most likely to cause acute limb ischaemia between an embolus and thrombosis?
- Embolus
- This is because when it comes to thrombosis there has been time for collaterals to form and so it is less severe
How can trauma cause acute limb ischaemia?
-The development of arteriovenous-fistula leads to shunting of the blood away from the limb
How can dislocations and fractures cause acute limb ischaemia?
-by the stretching of the arteries, the intima tears and the media and the adventitia stays intact because they have elastin
What is affected first by ischaemia?
Nerves and the reason why we feel pain and numbness first
What is affected last?
- muscles
- bones
- skin
How long can the limb survive before the ischaemia is irreversible?
6-8 hours?
What are the 6 P’s?
- Pain
- Pallor
- Paraesthesia
- Pulselessness
- Paralysis
- Perishingly cold
How does pain present in these patients?
- The pain is distal and then moves proximally
- the pain decreases as ischaemia develops further
How does paraesthesia present in these patients?
- is an early
- light tough>vibration>proprioception>(late)deep pain>pressure sense
How does pallor present in these patients?
- starts as pink discoloration even if pale
- it then becomes marble white
- then becomes gangrenous(black)
What is a mottled colour?
White with blue discolouration
How do we check for pulselesness?
- make sure we get a handheld Doppler an compare the veins and arteries
- compare to other nerves
How do you check for viability?
- make a cut and check for shiny and twitching (viable muscle)
- if dull with no twitching then not viable
3 degrees of severity:
- Viable: no immediate threat of tissue loss
- Threatened: salvageable if revascularised
- Non-viable: needs to be amputated because it cannot be salvaged
What does the severity of limb ischaemia depend on?
- Duration
- How big the obstruction is
- Whether there are collateral arteries around the obstruction or not
- the location
What are the characteristics of a viable limb?
- Pain: mild
- Capillary refill: intact
- Motor deficit: none
- Sensory deficit: none
- Arterial Doppler: audible
- Venous Doppler: audible
- Treatment: urgent work up
What are the characteristics of threatened limb?
- Pain: severely painful
- Capillary refill: delayed
- Motor deficit: partial
- Sensory deficit: partial
- Arterial Doppler: absent
- Venous Doppler: present
- Treatment: emergency surgery
What are the characteristics of non-viable limb ischaemia:
- Pain: variable
- Capillary refill: absent
- motor deficit: complete
- Sensory deficit: complete
- Arterial doppler: inaudible
- Venous doppler: inaudible
- Treatment: amputation
What is the management for acute limb ischaemia”?
- Doppler ultrasound to determine whether it is viable/threatened/non-viable and the location
- Analgesia
- Anticoagulation: IV heparin bolus of 3000-5000 units
Infusion of heparin IV 1000 units per hour - Give oxygen
- Make sure there are no extremes of temperature, correct hypotension
What investigations need to be done in these patients?
- ECG and CXR if above 40 yrs
- FBC, U&E, cardiacs enzymes
- Check for potassium, creatinine kinase and lactic acidosis for biochemical abmnormalities like muscle necrosis
4.
Would we do an angiogram in a patient with threatened limb?
No-there is no time
We only do it when there is a viable limb
What is an embolectomy done for?
-embolic occlusion
What is thrombolysis done for?
-thrombotic occlusion
What is an embolectomy?
- can be done with light Anaesthesia but anaethetist must be present especially if the patient is unwell-myocardial infarction
- the involved artery is clamped and arterotomy is made
- fogarty balloon catheter is inserted until it is distal to the clot
- the balloon is then inflated and the clot is pulled out with the balloon
- we flush with heparinised saline
- a warm foot indicates reperfusion
What do we need to ensure we do post-operatively?
- Reperfusion syndrome-oedematous muscles because of the increased pressure causing compartment syndrome
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What would a patient complain of if they had reperfusion syndrome?
- Calf pain
- Unable dorsiflex their ankle because the anterior compartment is affected first
- You need to do a 3 compartment fasciotomy
- Convert to warfarin for anti-coagulation until the INR is 2-2.5
What is catheter directed thrombolysis(CDT)
- An angiogram has to be done before the procedure to locate the blood clot
- The catheter is inserted into the clot and the thrombolytic agent is infused (streptokinase)
- this occurs for 6hours
- After 6 hours redo the the angiogram to see if there are clot remains
- Takes much longer than an embolectomy
What are the absolute contra-indications for catheter directed thrombolysis?
- CVA within 2 months
- Active bleeding
- Intracranial trauma
What is the mortality rate and success rate of embolectomy and thrombolysis
- Embolectomy- 20% mortality rate almost full success rate
2. Thrombolysis-10% mortality rate and 35% success rate
What is the differential diagnosis of acute limb ischaemia
- acute DVT
- blue toe syndrome
- venous insufficiency
- purple toe syndrome
What are the diagnostic tests for acute limb ischaemia?
- Initially- a arterial and venous doppler
2. Confirmatory test: angiography(DSA,CT angiogram and MRI angiogram
What is the differential diagnsosis of acute limb ischaemia?
- low cardiac output (shock)
- venous threatened limb
- Acute compressive neurology
- Guillain Barre
What is the gold standard for acute limb ischaemia?
CT angiogram
What is the aetiology of thrombus?
- aortic dissection
- hypercoaguable states-antiphospholipid syndrome
- artherosclerotic obstruction
- previous bypass
- trauma
What are the causes of hypercoaguable states?
- malignancy
- HIV
- antiphospholipid syndrome
- vasculitis-Takayasus arteritis
- heparin induced thrombocytopenia
What are the special investigations for acute limb ischaemia?
- CT angiogram
- Digital subtraction angiography
- Ultrasound
- MR angiography
What is the initial management of this patient if you see them in trauma?
- Supplemental oxgyen
- Analgesia
- Aspirin
- Unfractioned heparin
- IV fluids
- Prepare for intervention
What is percutaneous pharmacomechanical thrombectomy?
It is faster than normal lysis
What catheter is used in embolectomy?
- fogarty
What are the features of upper limb ischemia?
- older patients
- usually class 1 or 2a of rutherford classification
- caused by cardiac embolus
- complication is usually compartment syndrome
What is throracic outlet syndrome?
It is when the nerve is damaged which causes abnormality with te hand
What blood vessels are affected in thoracic outlet syndrome?
- superior cerebellar artery
- superior cerebellar vein
- brachial plexus
Who is most affected in venous thoracic outlet syndrome?
- young males that swim or lift weights
- treatment is to thrmobolyse and give anticoagulants for 3 months
What is the treatment for a arterial thoracic outlet syndrome?
scalenectomy, cervical rib resection
