Extracorporeal Removal Techniques

ECTR: Introduction & Indications - Clean Sweep Crew

• ECTR: "Clean Sweep Crew" for severe poisoning; removes toxins directly from blood.
• Key Goals: Remove toxin, correct severe metabolic issues, prevent organ damage.
• General Indications:
  • Severe poisoning with deterioration despite supportive care.
  • Lethal dose/concentration.
  • Impaired native clearance (renal/hepatic failure).
  • Toxin amenable to ECTR.
• Toxin Properties for ECTR:
  • Low Vd (< 1 L/kg)
  • Low protein binding (< 80%)
  • Small MW (< 500 Da)
  • High water solubility
• 📌 Key Toxins: Salicylates, Methanol, Ethylene glycol, Lithium, Phenobarbital, Theophylline.

⭐ ECTR is most effective for toxins with low volume of distribution (Vd < 1 L/kg) and low protein binding, ensuring efficient blood clearance.

ECTR: Hemodialysis & CRRT - The Big Guns

• Hemodialysis (HD):
  • Rapid removal of toxins using diffusion/convection. High-efficiency, intermittent.
  • Key Dialyzable Toxins: 📌 Mnemonic: "SLIME-PT"
    • Salicylates
    • Lithium
    • Isopropanol
    • Methanol, Metformin (with MALA)
    • Ethylene glycol
    • Phenobarbital (long-acting barbiturates)
    • Theophylline
    • (Note: Valproic acid (severe) can also be considered)
  • Ideal Toxin Properties: Low MW (<500 Da), water-soluble, low protein binding (<80%), small Vd (<1 L/kg).
  • ⚠️ Risks: Hypotension, disequilibrium syndrome, bleeding (heparin).
• Continuous Renal Replacement Therapy (CRRT):
  • Slower, continuous (24h) removal. Better for hemodynamically unstable patients.
  • Modes: CVVH (convection), CVVHD (diffusion), CVVHDF (both).
  • Use: Similar toxins to HD, especially if unstable or for toxins with rebound.

⭐ Hemodialysis is indicated for severe methanol or ethylene glycol poisoning with an osmolal gap, significant acidosis, or end-organ damage.

ECTR: Hemoperfusion & Plasma Exchange - Beyond Dialysis

• Hemoperfusion (HP)
  • Principle: Blood passes through a cartridge with adsorbent material (e.g., activated charcoal, resin).
  • Target toxins: Primarily lipid-soluble drugs and protein-bound substances.
  • Indications: Severe poisoning with theophylline, phenobarbital, carbamazepine, paraquat, amanita phalloides.
  • Limitations: Doesn't correct electrolyte/acid-base disturbances.
  • Complications: Thrombocytopenia (common), hypocalcemia, hypoglycemia, hypotension.
• Plasma Exchange (PLEX) / Plasmapheresis
  • Principle: Patient's plasma is separated from blood cells and discarded; replaced with colloid solution (e.g., albumin, FFP) or crystalloid.
  • Target toxins: Large molecular weight substances, autoantibodies, highly protein-bound toxins.
  • Indications: Amanita phalloides, thyroid storm, Guillain-Barré, Myasthenia Gravis, drug-induced TTP, some heavy metal poisonings.
  • Complications: Hypocalcemia (citrate toxicity), coagulopathy (dilutional), allergic reactions to replacement fluids, hypotension.

⭐ Charcoal hemoperfusion is particularly effective for paraquat poisoning if started early, ideally within 2-4 hours post-ingestion.

ECTR: Toxin Factors & Selection - Match Making Toxins

• ECTR Favored If Toxin Has:
  • Low Molecular Weight (MW): < 500 Daltons
  • Small Volume of Distribution (Vd): < 1-2 L/kg (📌 "Small Vd, Stays in Blood")
  • Low Protein Binding: < 80% bound
  • High Water Solubility (Hydrophilic)
  • Significant removal by ECTR compared to endogenous clearance (High ECTR clearance rate)

Selection matches toxin profile to ECTR type. Consider toxin's half-life and severity.

⭐ For toxins with high Vd (>2 L/kg) or high protein binding (>80%), standard hemodialysis is generally ineffective.

High‑Yield Points - ⚡ Biggest Takeaways

• Hemodialysis (HD): Best for water-soluble toxins, low Vd, low protein binding (e.g., Methanol, Ethylene Glycol, Salicylates, Lithium).
• Charcoal Hemoperfusion (HP): For lipid-soluble or highly protein-bound drugs (e.g., Theophylline, Phenobarbital).
• Indications: Severe poisoning, significant acidosis, organ damage, or failure of supportive care.
• Low Vd (<1 L/kg) is key for effective removal.
• Complications: Hypotension, bleeding, electrolyte shifts.
• CRRT: Slower, continuous removal for hemodynamically unstable patients.