Toxicology – Toxins and Conditions Treatable With Dialysis

Overview

Hemodialysis can enhance elimination of certain toxins, especially substances that are relatively small, water-soluble, have a low volume of distribution, and are not highly protein bound. It is also useful when poisoning causes severe acid-base abnormalities, kidney failure, or life-threatening clinical deterioration.

A classic memory aid for major dialysis indications is “AEIOU”, while several toxicologic agents are especially important to recognize.

Isopropanol

Hemodialysis can remove isopropanol, but it is rarely required.

It may be considered in exceptionally severe poisoning with:

• Profound hypotension
• Severe CNS depression
• Markedly elevated concentrations with clinical instability

Salicylates

Hemodialysis is an important treatment for severe salicylate poisoning.

It should be considered when there is:

• Severe neurologic toxicity
• Pulmonary edema
• Significant acid-base disturbance
• Kidney dysfunction
• Progressive clinical deterioration
• Very high serum salicylate concentrations

Clinical status is generally more important than relying on a single concentration cutoff.

Theophylline / Methylxanthines

Extracorporeal removal can be useful in severe theophylline toxicity, particularly when there is:

• Refractory hypotension
• Serious ventricular dysrhythmias
• Persistent or recurrent seizures
• Severe toxicity with markedly elevated serum levels

Uremia

Uremia results from accumulation of nitrogenous waste products in advanced kidney dysfunction.

Possible manifestations include:

• Nausea and vomiting
• Weakness
• Confusion or altered mental status
• Neuropathy
• Muscle cramps
• Seizures
• Pericarditis or pericardial effusion

Dialysis removes accumulated toxins and helps correct associated fluid, electrolyte, and acid-base abnormalities.

Methanol

Hemodialysis removes both methanol and formate, its major toxic metabolite.

It is especially important when methanol poisoning causes:

• Significant metabolic acidosis
• Visual abnormalities
• Kidney dysfunction
• Severe clinical deterioration
• High methanol concentrations

Dialysis is usually combined with inhibition of alcohol dehydrogenase using fomepizole.

Barbiturates

Dialysis may be considered in selected cases of severe barbiturate poisoning, particularly with long-acting agents such as phenobarbital and severe persistent toxicity.

Hemodialysis is generally more effective than peritoneal dialysis for toxin removal.

Lithium

Lithium is highly dialyzable and hemodialysis may be required in severe poisoning.

Important indications include:

• Significant neurologic toxicity
• Seizures or coma
• Kidney failure
• Serious cardiovascular instability
• Persistently high or rising lithium concentrations

Repeat dialysis may sometimes be necessary because lithium can redistribute from tissues back into the bloodstream after treatment.

Ethylene Glycol

Hemodialysis removes ethylene glycol and its toxic metabolites.

It may be needed when there is:

• Severe metabolic acidosis
• Acute kidney injury
• Major electrolyte abnormalities
• Severe clinical toxicity
• High ethylene glycol concentrations

Treatment is usually combined with fomepizole to prevent continued formation of toxic metabolites.

Key Points

• Dialysis decisions should be based on the patient’s clinical condition, laboratory abnormalities, toxin characteristics, and serum concentration, rather than a single number alone.
• Important dialyzable toxins include salicylates, lithium, methanol, ethylene glycol, and theophylline.
• Hemodialysis is usually preferred over peritoneal dialysis when rapid toxin removal is required.
• Severe neurologic toxicity, refractory shock, major acidosis, or kidney failure are common reasons to consider extracorporeal treatment.