Haemodialysis is effective at removing a number of low molecular weight, water-soluble poisons with a low degree of protein binding. It is indicated when elimination by other routes is unacceptably slow, especially if renal failure is contributing to this. The following agents are usefully removed:
|Inorganic acids (Acetic, Phosphoric, Formic)
Alcohols (ethanol, methanol*)
|Lithium : is the ideal poison for removal by dialysis. Renal tubular reabsorption leads to a renal clearance of 10-40ml/min when hydration is adequate, whereas haemodialysis can achieve clearances of up to 150ml/min. Some suggested indications for dialysis are:
Rebound is normal, because of intracellular stores and the fact that slow-release preparations are commonly responsible for poisoning. Try 6 hours of HD on a large kidney with maximal flow rates. Check levels 1-2h later.
|Salicylates Although there is a high degree of protein binding at therapeutic levels, this is saturated at toxic doses, and salicylates become more widely tissue distributed, extending half life 3 to 4-fold to 15-30h. Alkalinization of plasma and urine are beneficial.
Dialysis should be considered when
* Fomepizole is now first line therapy for methanol and ethylene glycol poisoning, but will often need to be used together with haemodialysis in severe poisoining. Ethanol can be used to inhibit metabolism of these compounds to toxic intermediates. It is less expensive, but harder to use effectively.
- Extrip provides very useful information at expert level for management of drug toxicity where dialysis or other extracorporeal treatments are recommended. See the list of Extrip recommendations.
- Poisons Units will give detailed advice for specific drugs. TOXBASE is invaluable for all types of poisoning. Using it requires registration. Contact A&E departments or local poisons unit for help with access. Edinburgh Renal Unit users – look on your noticeboard or in your email.
- Haemoperfusion over activated charcoal is more effective if poisons that are protein-bound in the circulation bind to it well. This applies to (for instance), theophylline, some anticonvulsants, procainamide. Practically this is now so rarely undertaken that obtaining the charcoal cartridge may be difficult.
Acknowledgements: Richard Phelps and Jane Goddard were the main authors for this page. The last modified date is shown in the footer.