Harvey's Garden

Acute limb ischemia

2 min read

Epidemiology/Risk Factors

  • Embolic (Most common): Atrial Fibrillation (cardiac source), recent MI (LV thrombus), prosthetic valve.
  • Thrombotic: Pre-existing Peripheral Arterial Disease (PAD), plaque rupture.
  • Trauma: Vascular injury (crush injury, invasive procedures).

Clinical Presentation

Classic 6 Ps:

  1. Pain: Earliest sign; severe, distal to obstruction.
  2. Pallor: Pale/waxy skin.
  3. Poikilothermia: Coolness to touch.
  4. Pulselessness: Absent distal pulses (check with Doppler).
  5. Paresthesia: Sensory loss (sign of nerve ischemia – indicates “threatened” limb).
  6. Paralysis: Motor loss (late/ominous sign – indicates potential non-viability).

Diagnosis

  • Best Initial Step: Clinical diagnosis + Handheld Bedside Doppler (arterial/venous signals).
  • Imaging:
    • Viable/Marginal Limb: CT Angiography (CTA) to plan revascularization.
    • Immediately Threatened Limb: Do not delay for imaging if sensory/motor loss is rapidly progressing. Go to OR.
  • Labs: CPK, Myoglobin (check for rhabdomyolysis), Lactate.

Management

  • Immediate Stabilization:
    • IV Heparin (Unfractionated): Start immediately to prevent propagation of clot. Do this before imaging if the diagnosis is highly suspected.
    • Dependent positioning of the limb (gravity helps perfusion).
  • Definitive Treatment (Based on Rutherford Classification):
    • Viable (Audible arterial Doppler, no neuro deficit): Catheter-directed Thrombolysis (tPA) or Urgent Surgery.
    • Threatened (Loss of sensation/motor, inaudible arterial Doppler): Emergency Surgical Revascularization (Embolectomy/Thrombectomy vs. Bypass).
    • Irreversible (Profound anesthesia, paralysis, rigor muscle): Amputation (revascularization leads to lethal reperfusion injury).

Key Associations/Complications

  • Compartment Syndrome: Occurs after reperfusion. Look for pain out of proportion to exam and pain on passive stretch. Tx: Fasciotomy.
  • Reperfusion Injury: Release of K+, acid, and myoglobin into circulation after clamp release. Can cause hyperkalemia (arrhythmia), metabolic acidosis, and renal failure (ATN).
  • Blue Toe Syndrome: Embolization of cholesterol crystals from proximal plaque. Intact pulses, painful cyanotic toes.

Graph View