Acute Limb Ischemia (shortcut)

• sudden decrease in limb perfusion with threat to limb viability
• 3 main causes: Emboli, thrombus, trauma
  
• Embolism: of relatively healthy arterial tree
  - originates from heart (MS with Af, MI with mural thrombus) or dilated diseased artery (aortic aneurysm)
  - suddenly occludes
  - usually arrests at arterial bifurcation (Aortic/iliac/femoral/popliteal bifurcation)
  
  
• Thrombus: of previously diseased arterial tree
  - Atherosclerosis: causes progressive narrowing
  - stimulates collaterals
  
  
• Must differentiate Embolus from Thrombus since Management is different
  Embolus: PECS (normal Pulse contralateral, known Embolic source, no Claudication, Sudden)
  
  
• HISTORY:
  1. Acute or not: sudden, severe, severity over time, duration
  DDx for acute ischemia (acute DVT/phlegmasia), hypoperfusion state (HF, Sepsis)
  * partial relief over time may be thrombus with collaterals
  
  2. Severity: numbness, weakness
  
  3. Etiology: Claudication, Heart disease, previous arterial surgery (cardiac cath)
  Atherosclerosis risks: Smoking, HTN, DM, lipids, family hx of CAD
  
  5P's
  
  Pain: symptom
  Pallor: early
  Pulselessness
  Paraesthesia
  Paralysis
  
  
• Pallor/Color
  - Early: pale
  - Late: cyanosed -> mottling -> fixed mottlling and cyanosis
  
  
• Pulse
  - palpate peripheral pulses (femoral, popliteal, posterior tibial, dorsalis pedis) and compare
  - temperature: cold
  - capillary refill: slow
  
  
• Paraesthesia: numbness will progress to anesthesia
  - progress of sensory loss
  1. light touch, vibration sense, proprioception = early
  2. deep pain, pressure sense = late
  
  
• Paralysis: advanced limb threatening ischemia
  - muscle turgidity: irreversible
  - intrinsic foot muscles first, then leg muscles
  - detecting early muscle weakness is hard because toe movements are produced by leg movements
  
  
• Classes of Acute Ischemia (Viable, marginal threat, immediate threat, irreversible)

• Investigations
  1. Doppler: assess level of obstruction and severity of ischemia
  2. If pedal signals are present = there is time for conventional arteriography and patient prep
  3. ABI: no value for acute ischemia, if it can be measured then the limb is not threatened
  
  4. Arteriography
  - high clinical embolic ischemia = no need for angiography
  - Do angiography if: (1) condition permits (2) unclear if thrombus or embolus
  - value
  (1) localizes obstruction
  (2) visualize arterial tree and distal run-off
  (3) can diagnose embolus (sharp cut off, reversed meniscus or clot silhouette)
  
  
• Treatment
  1. Heparin to avoid propagation
  2. Supportive: analgesia, keep foot dependent, avoid extremes of temperature, avoid pressure over heal, O2, correct hypotension, treat HF/Af
  3. Catheter Directed Thrombolysis (CDT): uses strepto/urokinase, TPA
  i: (1) class I, IIa (2) recent acute thrombosis (not for emboli, not for old thrombi)
  c/i absolute
  (1) stroke within 2 months
  (2) active bleeding or recent GI bleed within 10 days
  (3) intracranial trauma or NS within 3 months
  c/i relative
  (1) CPR within 10 days
  (2) major surgery or trauma within 10 days
  (3) uncontrolled hypertension
  
  4. Surgery
  - acute embolism: catheter embolectomy under LA
  - immediate surgical revascularization: class IIb
  or Class I, IIa when thrombolysis is not possible or contraindicated
  
  5. Combination
  6. Amputation: irreversible ischemia with permanent tissue damage (turgid muscle, fixed cyanosis)
  palpable popliteal pulse = below knee
  absent = above knee
  
  
  
  
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