Enhanced elimination
Related FACEM curriculum (2022) learning objectives:
- ME 3.8.1.6(d) Principles of management of toxicological presentations including: Indications for enhanced elimination
- Aim: Reduce severity and duration of intoxication by increasing elimination rate.
- Indications: Severe toxicity, poor outcomes with supportive care, slow endogenous elimination, suitable pharmacokinetics.
- Always preceded by resuscitation, supportive care, decontamination, and antidotes.
- Decision guided by risk-benefit analysis and pre-defined endpoints.
Multiple-Dose Activated Charcoal (MDAC)
Mechanism:
- Interrupts enterohepatic circulation: Charcoal binds drugs excreted into bile, preventing reabsorption.
- Gastrointestinal dialysis: Maintains drug gradient from blood to gut for small, lipid-soluble, low Vd drugs.
Indications:
- Carbamazepine coma: Reduces ventilation duration and ICU stay.
- Phenobarbitone coma: Rare; may reduce ICU stay.
- Dapsone overdose: Enhances elimination and shortens methaemoglobinaemia.
- Quinine overdose: Benefit debated; aggressive supportive care is primary.
- Theophylline overdose: Use only if haemodialysis unavailable or delayed.
Contraindications:
- Decreased consciousness without airway protection.
- Bowel obstruction.
Complications:
- Vomiting (30%), aspiration, constipation, bezoar formation, bowel obstruction, corneal abrasions.
Technique:
- Initial dose: 50 g (adults), 1 g/kg (children) orally or via NG tube.
- Maintenance: 25 g (0.5 g/kg in children) every 2 hours.
- Stop if bowel sounds absent or high NG aspirates.
- Reassess therapy every 6 hours; rarely required beyond 6 hours.
Urinary Alkalinisation
Mechanism:
- Alkaline urine ionises weak acids, reducing reabsorption and increasing excretion.
Indications:
- Salicylate overdose: Enhances elimination in symptomatic patients.
- Ineffective in chronic toxicity or severe cases requiring haemodialysis.
- Phenobarbitone coma: May reduce ICU stay; MDAC preferred.
Contraindications:
- Fluid overload.
Complications:
- Alkalaemia, hypokalaemia, hypocalcaemia (usually minor).
Technique:
- Correct hypokalaemia before initiation.
- Sodium bicarbonate: 1–2 mmol/kg IV bolus, followed by infusion (150 mmol in 850 mL 5% dextrose at 250 mL/h).
- Add potassium chloride to maintain normokalaemia.
- Monitor serum bicarbonate, potassium, and urine pH (>7.5).
Extracorporeal Techniques
Indications:
- Life-threatening poisoning with poor response to other measures.
Techniques:
- Haemodialysis: Preferred for small, low Vd drugs.
- Haemofiltration, haemoperfusion, plasmapheresis, exchange transfusion: Reserved for specific toxins.
Clinical Applications:
- Toxic alcohols: Methanol, ethylene glycol.
- Severe theophylline, salicylate, lithium, carbamazepine, valproate overdoses.
- Metformin lactic acidosis.
- Potassium overdose with life-threatening hyperkalaemia.
Considerations:
- Early initiation based on risk assessment.
- Intermittent haemodialysis preferred for higher clearance.
- Charcoal haemoperfusion rarely available.