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Acute Limb Ischaemia

Section: Vascular Sub-section: Curriculum, page 99

Definition

  • Sudden occlusion of a previously patent artery
    • Due to embolus, thrombosis, trauma or dissection
  • Characterized by the abrupt onset of
    • Severe pain
    • Coldness
    • Numbness
    • Motor weakness
    • Absent pulses in the involved extremity

Aetiology

  • Embolism
  • Thrombosis
  • Hypercoagulable state/Sepsis
  • Trauma
    • Endothelial injury causes aggregation of platelets & components of the clotting cascade
  • Dissection
  • Air
  • IVDU
  • Non-Occlusive mechanisms
    • Hypotension
    • Vasospasm

Embolism

  • Thrombotic Emboli
    • Heart source in 80-90%
      • 5-10% source unknown
      • Recent MI (within approximately 6/52)
      • 1/3 (ventricular mural thrombus)
      • AF 2/3 (atrial mural thrombus)
      • Prosthetic heart valves/ RHD/ Endocarditis with emboli forming in the dilated left atrium
    • Popliteal /Iliac aneurysms or (rarely) Aorta
    • Paradoxical Emboli
      • Venous thrombi migrating through a patent foramen ovale
  • Atheroembolism
    • Proximal atherosclerotic plaques (thoracic or abdo aorta) disrupted by trauma/intervention or spontaneously
    • Dislodge platelet rich thrombus AND cholesterol plaque
      • Often small and large debris that will occlude small and large vessels (Trash foot)
      • Far more difficult to treat

Thrombosis

  • Most common cause of Acute limb ischaemia
  1. Stenosing (ulcerated) atherosclerotic plaque or flow arrest in critical stenosis
  2. Thrombosed aneurysm
  • Results in laminar thrombus that can occlude popliteal artery or distal embolism that occlude tibial vessels
  1. Graft occlusion
  • Early = technical (inadequate run-off)
  • < 1 yr – Hyperplasia at anastomosis

  • 1 yr – Atherosclerotic plaque

  • Suggested by history of claudication, bilateral disease
    • Risk factors for PVD
  • Usually a degree of collateralization as is chronic
  • Most common = SFA
    • Also Popliteal Artery Aneurysms are predisposed

Hypercoagulable State/Sepsis

Aortic dissection

  • Severe sudden onset migratory pain
  • Stanford Classification
    • Type A – Ascending, 60%,
      • Elastic tissue degeneration (Marfans, Ehlers Danlos), younger
      • Rx: Surgical – Aortic replacement
      • MR 50% in first 24 hours, 90% 3/12
    • Type B – Descending
      • Smooth muscle degeneration in media, older patients
      • Rx – Medical (ß-blocker), stent, surgical
  • DeBakey Classification
    • I Whole length
    • II Ascending aorta – stops at Brachiocephalic
    • III Descending aorta – starts distal to Left Subclavian
    • IV enters descending to aortic valve

IVDU

  • E.g. Cocaine
  • Often partial obstruction, arteritis, thrombosis, spasm
  • Clinical – Pain & burning sensation characteristic
  • Rx; Heparinize, angiogram, vasodilators (papaverine, maybe dexamethasone), thrombolysis

Classification

  • Acute Limb Ischaemia
    • Rutherford Rutherford
      • Class 1 – Viable limb
        • Capillary return intact, no paralysis, no sensory loss
        • Dopplers present
      • Class 2a – Marginally threatened
        • Capillary return intact/slow, no paralysis, partial sensory loss
        • Arterial doppler absent, venous present
      • Class 2b – Immediately threatened
        • Capillary return slow/absent, partial paralysis, partial/complete sensory loss
        • Arterial doppler absent, venous present
      • Class 3 – Irreversible (needs amputation)
        • Absent staining, tense paralysis, complete sensory loss
        • Both arterial and venous dopplers absent

Pathology

  • Acute Phase
    • Insufficient substrate delivery: Glucose and O2
    • Anaerobic metabolism → Lactic Acidosis
    • Failure of ATP pumps:
      • Cellular damage
      • K+ release
      • Cytokine release
      • Oedema (due to ↑ membrane permeability)
      • ± 2° Bacterial Infections
  • Reperfusion injury
    • Generation of oxygen free radicals → Attach to FAs in phospholipids membrane ⇒ Mechanical & functional derangements
    • Release of ischaemic metabolites from muscle ischaemia leads to SIRS
    • Proteins (myoglobin), enzymes & K+ that are released from damaged cells are washed out to the circulation
    • ↑ Myoglobin → Acute renal impairment
    • ↑ K+ ⇒ Possible Arrhythmias
  • Compartment Syndrome
    • Pressure in the compartment becomes greater than the perfusion pressure
    • → ↑ Ischaemia
    • → ↑ Swelling > Secondary ischaemia

Clinical Presentation

  • Emboli

    • Usually large so lodge high
      • When it comes from atherosclerosis proximally it is usually smaller & more likely to present with a clinical syndrome similar to blue foot syndrome & be more difficult to fix
    • 70-90% lower limb
      • Main spot = Femoral Bifurcation
    • 10% upper limb (usually Brachial Artery)
    • Cerebral 10%
    • Visceral circulation 5%

  • 6 P’s

    • Pain
      • Sudden severe pain with emboli
    • Pallor
      • Initially reversible but with prolonged ischaemia there is hypoxic vasodilation resulting in rubor in dependent position (partly reversible)
        • With ongoing ischaemia there is thrombosis in capillaries/arterioles and rupture resulting in fixed blue staining and a mottled appearance (irreversible))
    • Paraesthesia
      • Important to determine if sensitivity to light touch maintained
      • These fibres are most susceptible to ischaemia and dysfunction heralds the beginning of irreversible ischaemic changes
    • Paralysis
      • Onset of motor paralysis implies impending gangrene
      • Swelling with ++ tenderness of a muscle belly (calf after femoral artery occlusion) usually denotes irreversible muscle ischaemia/infarction
    • Pulseless
      • Pulse immediately above may be particularly prominent – water-hammer
      • If contralateral pulses present be suspect of emboli
    • Polikothermia = ↓ Temp

  • Microemboli

    • Most significant when microemboli occlude a digital artery
      • Pain, cyanosis, coldness, numbness in affected digit
    • Usually improve over several days
    • Sudden onset differentiates embolism from other causes of blue toes
      • Vasculitis, Thromboangitis obliterans, trauma, chronic ischaemia
    • Multiple emboli → Trash foot / blue toe syndrome
    • Proximal pulses are intact

  • Thrombosis

    • More likely to result in reversible ischaemia
    • Acute on chronic limb ischemia
      • New onset rest pain
      • Usually with hx of claudication
    • Less ‘acute’ as more likely to have collaterals well established
    • Should always get pre-intervention imaging
      • CTA or MRA
    • Ideally management with
      • Thrombolysis +/- Angioplasty +/- Stent
    • If unsuccessful may need bypass
      • Always need good run-off vessels for bypass

Investigations

  • Bloods
    • FBC, U+E, Coags, G+H
  • ECG -
  • CXR
  • CT Angiogram
    • Imaging of choice in the acute setting
    • MRA is alternative
  • Transoesophageal ECHO to demonstrate thrombus
    • Often do this post-op, Can flag if in AF
  • ABPI – limited value in acute ischaemia
    • Except in acute on chronic ischaemia

Management

Emergency Management

  • Analgesia
  • O2
  • IV fluid
  • Heparinize 5000IU bolus then infusion. Stop 4-6 hours pre-angio
    • Aim: Prevent thrombosis resulting from stagnant flow beyond 1° occlusion
    • Would continue past intervention if had a source which wasn’t corrected
      • Stay on anticoagulation re-embolization rate 7%
      • No anticoagulation re-embolization rate 21%
      • Risk of heparin induced thrombocytopenia 5%
  • Assess reversibility and manage accordingly
  • Use Rutherford Classification
    • Lower extremity may be salvaged after up to 5-6 hours of profound ischaemia
    • Class 1 – Viable limb
    • Class 2a – Marginally threatened
    • Class 2b – Immediately threatened
    • Class 3 – Irreversible (needs amputation)

ViableMarginally threatenedImmediately threatenedNonviable
PainMildModerateSevereVariable
Capillary refillIntactDelayedDelayedAbsent
Motor deficitNoneNonePartialComplete, paralysis (rigor)
Sensory deficitNoneNone or minimal (toes)More than toesComplete, anesthetic
Arterial DopplerAudibleInaudibleInaudibleInaudible
Venous DopplerAudibleAudibleAudibleInaudible
TreatmentUrgent evaluationUrgent revascularizationEmergency revascularizationAmputation

Threatened but Reversible Ischaemia

  • Rutherford category I or IIa:
    • Usually presents as new onset rest pain
    • Not paralysis and no sensory change
  • Usually due to thrombosis rather than embolus
  • Time available to plan intervention
    • CTA or MRA
  • Management more complex
    • Often have diffuse disease at multiple levels
    • Variable collateralization Unpredictable run-off
  • No neurological deficit
    • Thrombolysis
  • Neurological deficit is present
    • Reconstruction (if run-off is OK)

Partly Reversible Ischaemia

  • Rutherford category IIb: Immediately threatened
    • White limb with sensory/motor deficit
  • Embolus most likely, esp. if
    • Rapid onset
    • No prev hx of claudication
    • Normal contralateral pulses
    • Probable embolic source (AF, cardiomyopathy, AAA)
  • Surgery most appropriate - Embolectomy
    • CT-A helpful but “should NOT delay surgery” although in this day and age it is unlikely that a CTA is not able to be performed/not done
  • Thrombolysis not appropriate
  • Prepare both groins and lower limbs
    • If embolectomy not effective can do Fem-Fem Cross-over bypass

Irreversible Ischaemia

  • Rutherford Category III:
    • Muscle paralysis, tense swollen fascial compartments, fixed staining
    • 10% of pts
  • Consider pt’s condition and level of ischaemia
  • Revascularisation inappropriate
  • If high level and moribund patient
    • Palliative care
  • If level treatable by amputation and pt appropriate for amputation
    • Resuscitate/stabilize and amputate limb
    • Amputation considered as primary management if QOL / mobility poor
      • or if disease is unreconstructible or if there is extensive tissue loss
        • Even for partly reversible disease

Non-Operative Management

  • Sometimes considered for emboli to major arteries in the upper extremities where collateral circulation is outstanding
  • Or for rare event where signs & symptoms spontaneously resolve after an initial ischaemic episode
  • Can consider Iloprost
    • Prostacyclin
      • ↓ Platelet aggregation
      • Dilatation of arterioles & venules
      • Inhibition of leukocyte adhesion
    • Indications: Buerger’s disease (when revascularization is not indicated/possible) or Raynaud’s

Post-Intervention Cares

  • Consider fasciotomy after prolonged ischaemia
  • Anticipate renal insufficiency from myoglobin release after reperfusion of ischaemic muscle
  • Consider ECHO/CT-A if not done before to determine site of embolus if patient not in AF
  • Will help guide ongoing anticoagulation therapy and may require treatment

Thrombolysis

Indications

  • For acute thrombosis
    • Achieved by stimulating conversion of plasminogen to plasmin
      • A protease that degrades fibrin
      • Results in thrombus dissolution
    • Must be injected via angiography
      • AT THE SITE of thrombus
      • Otherwise ineffective and high risk of complications
  • Short segment thrombotic occlusions
    • Catheter directed followed by balloon angioplasty to underlying offending lesion
  • Ischaemic interval short
    • Can be used up to 1-2/52 post initial event

Contraindications

  • 5 Absolute (active or high risk of active bleeding)
    • CVA within 2 months (or TIA)
    • Neurosurgery within 3 months
    • Intracranial trauma within 3 months
    • Active bleeding or bleeding diathesis
    • Recent GI haemorrhage (<10 days)
  • 5 Relative
    • CPR within 10 days
    • Uncontrolled hypertension
    • Major trauma (10 days) or Major surgery within 2 weeks
    • Puncture of incompressible vessel
    • Intracranial tumour
    • Minor
      • Liver failure
      • SBE
      • Pregnancy

Agents Used

  • rTPA (Recombinant Tissue Plasminogen Activator)
    • Streptokinase
    • Urokinase (probably superior)
  • Heparin given concurrently
    • Prevents clot formation around catheter, prevents early re-thrombosis & for 48 hours after
  • Consider life-long Warfarin
    • or Aspirin + Clopidogrel if warfarin contraindicated

Technique

  • Need to deliver to site of thrombus
  • Intra-thrombus method
  • Initial bolus dose followed by infusion for up to 3 days
    • Duration is dictated by reassessment
  • Occasionally can be supplemented with percutaneous thrombectomy
    • Suction/aspiration or disruption and net catchment
    • Not really recommended for distal vessels and can cause further arterial damage

Results

  • Recanalization rate 80-90%
  • Allows demonstration of underlying anatomy
  • Better planning subsequent surgery if required

Complications

  • 1% MR (5-10% MR in 30 days – mostly MI or CVA)
  • CVA – 3%
  • GI bleed rare
  • Bleeding at catheter site up to 40%
  • Haemorrhage requiring transfusion 5%
    • Usually at groin but can be retroperitoneal or intra-abdominal
    • Manage with Aprotinin (plasmin inhibitor), RBC (or whole blood), FFP + Fibrinogen
  • Distal embolus – 2-3%
  • Allergic reaction

Compartment Syndrome

Definition

  • Compartment syndrome occurs when increased pressure within a compartment compromises the circulation and function of the tissues within that space
    • Pressures increase beyond capillary perfusion pressure (30mmHg)
    • Due to muscular swelling within the confines of an unyielding osseofascial bound space

Aetiology

  • Orthopaedic
    • Fractures and fracture surgery
  • Vascular
    • Arterial and venous injuries
    • Reperfusion injury
    • Haemorrhage
    • Phlegmasia caerulea dolens
  • Soft tissue
    • Crush injury
    • Burns
  • Iatrogenic
    • Prolonged limb compression
    • Puncture in anticoagulated patients
    • Use of a pneumatic antishock garment
    • Casts and circular dressings
    • Pulsatile irrigation
  • Occasional
    • Snakebite
    • Overuse of muscles
    • Chronic exertional compartment syndrome in runners

Clinical Presentation

  • Severe out of proportion pain on examining compartment and passive movement
  • Paraesthesia often first sign
  • Check by compartment
  • Pallor, decreased capillary refill, perishing cold
  • Doppler can be intact until late

Investigations

See: Fasciotomy

Embolectomy

Principles

  • Prepare the whole limb and lower abdomen and contralateral side to mid-thigh
    • Because you don’t know exactly where problem is
    • You can evaluate your success (foot in transparent plastic bag)
  • Embolectomy via Fogarty balloon catheter placed through a proximal arteriotomy
    • Sizes 2-7 available (Fogarty)
    • Check balloon with saline first
  • Catheter passed in 10cm increments
    • Gentle inflation
    • Resistance free withdrawal
  • Repeat until no more clot, and good back flow
    • Back flow not a reliable sign though
  • Heparinize distally 5000 IU in 250mL
  • Can use intraoperative direct arterial infusion of urokinase (50,000-250,000 units) in settings where cleared proximal disease but might be left with some stagnant thrombosis which can’t clear
  • For an aortic bifurcation saddle embolus
    • Will often do bilateral femoral cut-downs, clamp both sides and clear
    • To avoid forcing trash down one side
  • Always do arteriogram on completion

Femoral Embolectomy

  • Setup and Positioning
    • Fogarty size 3 or 4 for Femoral
      • Sizes 2-7 available – 2 – smallest
      • Check the balloon
    • Prepare both limbs and lower abdomen completely (can wrap feet in transparent plastic bags)
      • E.g. If you identify an aortic bifurcation saddle embolus will need to do bilateral femoral cut downs, clamping both sides before starting to clear so trash doesn’t get thrown down one side
    • Thigh abducted, knee on pillow
      • NB: Mid-inguinal point – ASIS Pubic Symphysis
        • Femoral Artery
      • NB: Mid-point of the inguinal ligament; ASIS to Pubic Tubercle
        • Femoral Nerve
  • Incision and Control
    • Longitudinal skin incision at mid-inguinal point
    • Divide skin, subcutaneous tissue
    • Superficial & deep fascia, vascular sheath
    • May come across superficial branches of GSV/ Femoral Artery
      • Control Common femoral artery, superficial femoral artery, PFA individually with vascular loops
        • Encircle vessels by working medial to lateral under vessels with right angles
        • Avoid damage to Femoral Vein
      • Identify PFA as the one with the branches
    • Before opening – 5000 IU heparin
    • Take into account body weight, renal function
  • Embolectomy
    • Before opening – 5000 IU heparin (take into account body weight, renal function)
    • Just above bifurcation make
      • Transverse cut if artery normal & unlikely to need to re-construct
      • Longitudinal if diseased, will often need to close with patch to prevent stenosis
        • Transverse arteriotomies are more predisposed to flaps & you are limited with the size of the cut you can make (therefore problematic in small vessels)
        • Longitudinal arteriotomies: More prone to stricturing
          • Will accept up to 50% stenosis
    • Use size (3) 4 catheter mostly
    • Do proximal (common), then SFA then PFA
    • Catheter passed in 10cm increments, gentle inflation, resistance free withdrawal
    • Repeat until no more clot, good back flow
    • Check distal pulses
    • Check other side pulses
    • From here if placed distally
    • Generally can enter peroneal artery
    • If want ATA or PTA, make separate distal (below knee) incision
  • Closure and Considerations
    • Once finished
    • Flush with heparinized saline
    • Arteriogram can be done if facilities/ experience available but not if unexperienced in technique
    • Transverse arteriotomy closed with 4/0 or 5/0 Prolene
    • Consider about fasciotomy

Popliteal Embolectomy

  • Leg abducted, hip & knee flexed, externally rotated
  • Standard medial incision
  • Parallel to long axis of leg,
  • 1 finger breadth posterior to medial border of Tibia
  • Approximately 10cm long, preserve LSV
  • Fat, fascia & deep fascia divided
  • Medial head of gastrocnemius mobilized & retracted posteromedially
  • Soleus taken down off tibia to expose Tibioperoneal Trunk
  • Get individual control (sometimes take ATV to aid dissection)
  • Distal popliteal arteriotomy (usually longitudinal)
  • Use size (2) 3 catheter for embolectomy
  • Close with graft or vein patch

Brachial Embolectomy

  • Longitudinal incision just above elbow
  • Exposed at Medial border of Biceps
  • In the groove between Biceps & Triceps
  • Deep fascia is incised & the groove opened up to display the neurovascular bundle embedded in connective tissue
  • Size 3 catheter for embolectomy

.7-.9 - long distant .5-.7 - short distant .3-.5 - ischaemic rest pain <.3 - tissue loss, gangrene

Toe pressure

  • ABPI is inaccurate in diabetes
  • Normal toe pressure >70
  • If >40 then an amputation will heal

Graph View

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