Enhanced Elimination

Introduction

Enhanced elimination aims to reduce the severity and duration of an intoxication.  As with decontamination, the decision to proceed with enhanced elimination techniques requires a thorough risk/benefit analysis and shouldn’t interfere with resuscitation or good supportive care.  It is only available for ingestions with the toxicokinetics amenable to elimination, in particular the volume of distribution and clearance of the drug in question needs to be considered.

Methods of Enhanced Elimination include:

  • Multi Dose Activated Charcoal
  • Urinary Alkalinisation
  • Extracorporeal Techniques

Multi Dose Activated Charcoal (MDAC)

MDAC enhances elimination through the interruption of enterohepatic recirculation and also through gastrointestinal dialysis.  MDAC can be considered for a potentially toxic overdose of a drug with a long half-life but small volume of distribution. Complications include constipation, aspiration and obstruction.

Give 50g stat then 25g q2-4h monitoring for abdominal distension and presence of bowel sounds

Substances amenable to MDAC:

  • Carbamazepine
  • Phenytoin
  • Dapsone
  • Phenobarbitone
  • Quinine
  • Theophylline
  • Cardiac glycosides

Urinary Alkalinisation

Urinary alkalinisation increases the elimination of acidic drugs by increasing the proportion of drug in the ionised state in the renal tubules preventing reabsorption. Complications include hypokalaemia, hypocalcaemia, hypernatraemia and fluid overload.

Give 1-2 mmol/kg sodium bicarbonate bolus followed by an infusion of 25 – 50mmol/h.  Monitor urinary pH q2h, aiming for a pH > 7.5. Measure VBG q2h and replace potassium to ensure K > 3.0 mmol/L.

Substances amenable to Urinary Alkalinisation:

  • Salicylates
  • Phenobarbitone
  • Chlorphenoxy herbicides

Extracorporeal Techniques

Extracorporeal techniques of elimination are invasive and are reserved for life threatening intoxications which will not respond to supportive care or antidote administration alone.

Overall approach for the consideration of extracorporeal therapy in poisoning1

Haemodialysis is the most common technique employed and can be provided in most intensive care units.  It is suitable for water soluble toxins which are small, not highly protein bound, with a small volume of distribution. IHD is the preferred mode of haemodialysis where available to manage poisonings, followed by SLED, then CVVHD. 

Substances amenable to dialysis include:

  • Lithium
  • Salicylates
  • Toxic Alcohols
  • Valproate
  • Potassium
  • Theophylline
  • Lamotrigine
  • Carbamazepine

Dialysis is also frequently used in poisonings to correct acidosis.  A good example is metformin induced lactic acidosis.

Further reading

  • Ghannoum M et al. ‘Use of extracorporeal treatments in the management of poisonings.’ Kidney International 2018; 94(4):682-688
  • EXTRIP www.extrip-workgroup.orgprovides recommendations for extracorporeal elimination techniques for specific drugs

References

  1. Ghannoum M et al. ‘Use of extracorporeal treatments in the management of poisonings.’ Kidney International 2018; 94(4):682-688