Acute Limb Ischaemia

IS A MEDICAL EMERGENCY

1. Initial Stabilization
2. Focussed History/Examination
3. Baseline investigations
4. Urgent surgical r/v
5. Anticoagulation – IV heparin
6. Arrange angiography if considered necessary
7. Surgery within 12 hours of onset of symptoms

 

Definition

• Sudden onset of severe ischaemia  induced by distal embolization of proximal atheromatous material to the toes, resulting in the blue toe syndrome, by a large embolus, or to sudden occlusion of a previously stenotic area causing diffuse acute limb ischemia. 
  • Blue toe syndrome (see below)
  • Diffuse acute limb ischemia — sudden onset of pain progressing to numbness and finally paralysis of the extremity, accompanied by five “P”

 

Aetiology

• Embolus
  • 60%-30% cardiac AF/AMI (↑sed risk if large and ant. Infarct)
  • 30% undetermined 
  • 2% proximal aneurysm
• Thrombotic
  • 30% superimposed on pre-existing atherosclerosis
  • 2% aneurysm – thrombotic occlusion
• Infrequent
  • Venous thrombosis
  • Spasm
  • Extrinsic compression
• Other (Trauma,  Drug-induced arterial spasm e.g. ergot alkaloids)

 

Site: 

    Most common site of blockage is the SFA at the adductor Canal.

 

Assessment

 

 Presentation 

• Rest Pain: SOCRATES(note 5 Ps)?
  • Severe ,  not readily controlled by analgesics
  • Location: typically localized in the forefoot toes of the chronically ischemic extremity. 
  • made worse by elevation
  • relieved by limb dependency
  • is often worse at night or while reclining – perfusion further ↓when lying down due to ↓ CO at night, ↓ effect of gravity

 

• Onset
  • sudden ischemic symptoms in a previously asymptomatic patient is most consistent with = embolism
  • gradually increasing symptoms in a patient with chronic ischemia = thrombotic

 

• SSx of PVD: Intermittent claudication, risk factors, rest pain, suggestive of thrombotic episode

• Limb Trauma

• • Embolic source
  • AF(Palpitations?)

• AMI (Chest pain/angina?)

• Valvular lesions
• Atherosclerosis
• Hx of TIA, bowel ischaemia

• Other sig. co-morbidities e.g. CAL etc. (important in terms of pre-op/anaesthetic assessment)

 

Risk Factors for Atherosclerosis/Ischaemic Heart Disease 

• Smoking
• Hypertension
• Hypercholesterolaemia
• Obesity
• Family history
• Diabetes mellitus

 

Medications/Allergies

• β-blockers
• Warfarin
• Previous thrombolysis with streptokinase
• Past anaesthetic history

 

Examination

• Pulse – AF
• Limb
• Pain (note:may be absent in some pts due to prompt onset anaesthesia, paralysis)
• Pallor
• Pulseless
• Paraesthesia – Light touch lost before pressure, pain, temperature sensation (because these larger fibres are relatively less susceptible to hypoxia)
• Paralysis
• Perishingly cold
• Pistol shot onset
• Late signs: Mottling and muscle rigidity (local rigor mortis) > 4-6/24 
• Other leg: normal?

 

• SSx of chronic ischemia
  • atrophy of the skin
  • hair loss
  • thickened nails
  • ischemic ulcers
  • gangrene

 

• Neurologic examination
  • sensory deficits
  • early signs of dysfunction
  • numbness /paresthesias (dorsum of the foot)
  •  advanced ischemia
  • Major loss of sensory or motor function 
  • most sensitive to ischemia 
  • Anterior compartment of the lower leg

• Blue toe syndrome 

• • sudden appearance of a cool, painful, cyanotic toe or forefoot with confusing presence of strong pedal pulses and a warm foot  
  • scattered areas of petechiae /cyanosis of the soles of feet. 
  • due to embolic occlusion of digital arteries with atherothrombotic material from proximal arterial sources.

 

• CVS – AF, aneurysms, signs of cardiac failure
• Respiratory – from pre-anaesthetic point of view

 

Is the limb viable?

• Viable — Viable limbs are under no immediate threat of tissue loss
• Marginally threatened — Marginally threatened limbs are salvageable if treated promptly
• Immediately threatened — Immediately threatened limbs are salvageable with immediate revascularization. 
• Irreversible (nonviable) — Irreversible limbs have major tissue loss and/or permanent nerve damage. Require major amputation regardless of the therapy that is instituted. Revascularization may be required to permit healing of the amputation or amputation at a lower level. 

 

• SVS/ISCVS classification of acute extremity ischemia 

	Viable	Threatened	Nonviable /irreversible
Pain	Mild	Severe	Variable
Capillary refill	Intact	Delayed	Absent
Motor deficit	None	Partial	Complete
Sensory deficit	None	Partial	Complete
Arterial Doppler	Audible	Inaudible	Inaudible
Venous Doppler	Audible	Audible	Inaudible
Treatment	Urgent work-up	Emergency surgery	Amputation

• If the limbs viability is not in question then proceed to Ix
  1. Listen for Bruits, ABPI
  2. Duplex, Angiography

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Management

1. Help – urgent surgical review!! 
2. Monitored bed

1. Airway
2. Breathing – pulse oximeter
3. Circulation
   1. IV access
   2. Baseline Bloods – FBC, UEC, LFT’s, coags (APTT/PT/INR), G&H
   3. ECG
4. Aspirin – if pt not already on aspirin, give 300mg PO
5. Protect limb, but do NOT elevate – e.g. with a cage and heel pad

 

1. Initiate Anticoagulation – IV heparin
   1. Anticoagulation will prevent further propagation of thrombus, and inhibit thrombosis distally in the arterial and venous systems due to low flow and stasis. Time is crucial
   2. 5000U IV bolus (or 70-80U/kg if using weight based regime)
   3. Then 1250U/hr IV infusion (20U/kg/hr)
   4. Measure APTT after 6 hours and adjust accordingly
   5. Target APTT approximately 1.5-2 x baseline value
2. Analgesia
3. Assess fitness for surgery