Acute Limb Ischemia

Limb ischaemia (ALI) is defined as a sudden decrease in limb perfusion

Classification Of Limb Ischemia

According to the onset

  1. Acute limb ischemia
    • Ischaemia < 14 days
  2. Acute on chronic limb ischemia
    • Worsening symptoms and signs of an already ischemic limb
  3. Chronic limb ischemia
    • Ischaemia stable for > 14 days


According to the severity

  1. Incomplete
    • Limb is not threatened
  2. Complete
    • Limb is threatened
  3. Irreversible 
    • Limb has become non viable
 
Causes Of Limb Ischemia
  1. Thrombus (60%)
    • Thrombotic occlusion of an pre-existing stenotic arterial segment 
  2. Embolus (30%)
    • Atrial fibrillation
    • Aneurysms 
    • Post myocardial infarction 
    • Prosthetic by pass grafts 
 
 
Management Of Acute Limb Ishcemia
Clinical features6 P's Of Ischemia
  1. Pain 
  2. Pallor
  3. Pulseless
  4. Perishing cold
  5. Paraesthesia
  6. Paralysis 
* Paraesthesia and paralysis are the key signs of diagnosing complete ischemia demanding immediate surgical treatment 
 
Investigations
  1. No investigations are required
 
Treatment
  1. Intravenous bolus of heparin 
    • To limit propagation of thrombus
    • To protect collateral circulation 
    • Contraindications include….
      • Acute aortic dissection 
      • Multiple trauma
      • Serious head injury
  2. Embolectomy (Definitive treatment)
  3. If unsuccessful, thrombolysis
    • Streptokinase 
    • Urokinase
    • Alteplase
  4. Postoperatively heparin is given followed by warfarin 
    • Heparin is given 6 hours after surgery (Given before may cause hematoma formation)
    • Heparin is given to prevent formation of emboli
    • Warfarin is given to prevent recurrent embolism 
    • Should be avoided, if contraindicated 
  5. Fasciotomy 
    • In delayed presentation to buy some more time 
 
 
Post-Ischemic Syndromes
  1. Reperfusion injury
  2. Compartment syndrome
  3. Chronic pain syndromes


Reperfusion Injury

 
Reintroduction of oxygenated blood after a prolong period of ischaemia
              ↓
Generation of free radicals 
              ↓
Activation of neutrophils
              ↓
Migrate into the reperfused tissue
              ↓
Injury to the tissues
              ↓
Damaged endothelial cells become more permeable.
 
 
Effects of reperfusion syndrome
  • Local 
    • Limb swelling leading to compartment syndrome
    • Impaired muscle function 
    • Muscle infarction leading to muscle contracture
  • General 
    • Acidosis
    • Hyperkalaemia (Due to leakage from the damaged cells)
    • Heart
      • Cardiac arrhythmias
    • Kidney
      • Myoglobinaemia 
      • Acute tubular necrosis
    • Lungs
      • Acute respiratory distress syndrome
    • GIT
      • Gastrointestinal endothelial oedema

 

 
Compartment Syndrome
 
High rise of pressure within a closed osteofascial compartment leading to neurovascular compromisation is called compartment syndrome
 
Pathophysiology of compartment syndrome
 
Injury to the tissues within a closed fascial compartment 
              ↓
Increased capillary permeability and oedema 
              ↓
Increase intestitial pressure
              ↓
Reduced blood supply to viable tissues
              ↓
Further ischemic tissue injury & swelling 
              ↓
A vicious circle is setup
              ↓
Compartment syndrome
              ↓
Muscle necrosis, skin necrosis & limb loss
 
Clinical features 
  1. Swelling and pain on squeezing the muscle (Calf)
  2. Pulse – Maybe present / Absent (Palpable pedal pulses do not exclude compartment syndrome)
 
Treatment
  1. Fasciotomy 
 
Complications Of Compartment Syndrome
  1. Muscle necrosis 
  2. Limb loss 
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