When to stop hemodialysis (hemodialysis) in a patient with alcohol toxicity, including methanol or ethylene glycol poisoning, or severe ethanol poisoning, with or without underlying liver disease or other comorbidities?

When to Stop Hemodialysis in Alcohol Toxicity

Stop hemodialysis when the anion gap (calculated as Na+ + K− − Cl− − HCO3−) is < 18 mmol/L, the toxic alcohol concentration is < 4 mmol/L (25 mg/dL for ethylene glycol), and all acid-base abnormalities are corrected. 1

Specific Cessation Criteria by Toxin Type

Ethylene Glycol Poisoning

Primary cessation endpoints (all should be met):

• Anion gap < 18 mmol/L (calculated with potassium) - this is the strongest recommendation 1
• Ethylene glycol concentration < 4 mmol/L (25 mg/dL) - suggested endpoint 1
• Complete correction of acid-base abnormalities - including normalization of pH and bicarbonate 1

The EXTRIP workgroup emphasizes that the anion gap cutoff of < 18 mmol/L is the most reliable cessation criterion, as it reflects clearance of toxic metabolites (particularly glycolate) rather than just the parent compound. 1 Some authors have proposed that ethylene glycol < 10 mmol/L may be acceptable in asymptomatic patients, but supporting data are insufficient and there are minimal downsides to continuing until the lower 4 mmol/L threshold is reached. 1

Methanol Poisoning

Apply the same cessation criteria as ethylene glycol:

• Anion gap < 18 mmol/L 1
• Methanol concentration < 20 mg/dL 2
• Resolution of metabolic acidosis with normal pH 2

The rationale is identical - both methanol and ethylene glycol produce toxic acid metabolites (formic acid and glycolic acid respectively) that drive the anion gap elevation. 3, 4

Severe Ethanol Poisoning

For pure ethanol intoxication requiring dialysis (rare):

• Clinical improvement with restoration of consciousness 5
• Ethanol level reduced to non-life-threatening range (typically < 100 mg/dL) 5
• Hemodynamic stability achieved 5

Critical Technical Considerations

Rebound Phenomenon

• Do not stop dialysis prematurely based on a single measurement - ethylene glycol and methanol can redistribute from tissues back into plasma after dialysis cessation 1
• If rebound occurs with recurrent symptoms or rising anion gap, repeat hemodialysis session is indicated 1
• Continue ADH blockade (fomepizole or ethanol) if dialysis must be terminated before reaching target concentrations 1

Antidote Management During Dialysis

• Increase fomepizole dosing to every 4 hours during hemodialysis (from standard every 12 hours) because it is dialyzable 2, 6
• Increase ethanol maintenance rate to 250-350 mg/kg/hour during dialysis (from standard 100-150 mg/kg/hour) and monitor levels every 2-4 hours 2
• Some centers withhold ADH blockade during dialysis, but this approach cannot be recommended due to insufficient safety data 1

Duration Estimation

• Validated formulas can predict required dialysis time based on initial toxin concentration, patient's total body water (Watson equation), and dialyzer clearance: Required time (hours) = [-V ln(5/A)]/0.06k, where V = total body water in liters, A = initial toxin concentration in mmol/L, and k = 80% of dialyzer urea clearance in mL/min 7
• This formula assumes high-efficiency hemodialysis with good constant blood flows and targets a 5 mmol/L endpoint 7
• Useful for planning purposes, especially when multiple poisoned patients require triage, but all acid-base abnormalities must still be reversed before stopping 1, 7

Common Pitfalls to Avoid

Do Not Stop Based on Clinical Improvement Alone

• Never discontinue dialysis based solely on improving mental status or hemodynamics - the anion gap and toxin levels must meet cessation criteria 6
• Patients may appear clinically improved while still having dangerous levels of toxic metabolites 6

Do Not Rely on Osmolal Gap for Cessation

• The osmolal gap is useful for diagnosis and initiation decisions but has too many imprecisions at low values to guide cessation 1
• As toxic alcohols are metabolized, the osmolal gap decreases while the anion gap increases - focus on anion gap for stopping decisions 8, 4

Monitor for Complications

• Alcohol withdrawal syndrome is common in patients with alcohol use disorder, especially during dialysis when ethanol is rapidly removed - implement prophylactic benzodiazepines 1
• Hypophosphatemia and hypokalemia can occur during prolonged dialysis - use phosphorus and potassium-enriched dialysate 4
• Osmotic disequilibrium is theoretically possible with extremely high concentrations (> 100 mmol/L) but rarely reported 1

Special Consideration for Multiple Toxin Ingestion

• When multiple toxic alcohols are co-ingested (e.g., ethylene glycol + methanol + diethylene glycol), the kinetics are altered due to competitive ADH inhibition 8
• In these cases, maintain a high index of suspicion and continue dialysis until all acid-base abnormalities resolve, as standard concentration targets may not apply 8

When Dialysis Can Be Stopped Early

The only acceptable scenario for early termination:

• Multiple poisoned patients requiring triage with limited dialysis resources 1
• In this situation, continue ADH blockade (fomepizole or ethanol) to prevent further metabolism until dialysis can be resumed 1
• Otherwise, there is no clinical justification for stopping before meeting all cessation criteria 1