skip to main content

Severe chronic lithium toxicity — MRCEM SBA MCQ

Instant feedback + full explanation. One question, done properly.

HardToxicology and environmental emergenciesSevere chronic lithium toxicityMRCEM SBA

A 68-year-old woman taking lithium for bipolar disorder is brought to the emergency department after three days of diarrhoea and reduced fluid intake. She also started taking ibuprofen for knee pain four days ago. She has taken no extra lithium tablets. She has coarse tremor and marked ataxia; over two hours in the department, her GCS falls from 15 to 11. She is breathing adequately and currently protecting her airway. Her blood pressure is 124/76 mmHg, capillary glucose is 6.2 mmol/L, serum lithium is 1.9 mmol/L and creatinine is 230 µmol/L, compared with 85 µmol/L previously. Lithium and ibuprofen have been withheld, intravenous 0.9% sodium chloride has been started, and critical care is assessing her airway. Which additional management decision is most appropriate now?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: B — Arrange urgent intermittent haemodialysis with renal and poisons specialists.

This is severe chronic lithium toxicity: fluid depletion and acute kidney injury impair lithium elimination, while progressive reduction in consciousness demonstrates substantial neurological toxicity. The lithium concentration of 1.9 mmol/L must not be used as a reason to defer escalation. UK product guidance advises considering haemodialysis for marked neurological features or severe symptoms regardless of serum concentration. Urgent renal and poisons-service discussion should therefore proceed alongside resuscitation, airway assessment and serial monitoring. ([medicines.org.uk](https://www.medicines.org.uk/emc/product/10828/smpc)) A is attractive because withholding lithium and restoring circulating volume are essential, but observing for another concentration delays assessment for extracorporeal treatment in a deteriorating patient. It would better suit a clinically stable patient with mild toxicity. C offers extracorporeal clearance, but intermittent haemodialysis is the preferred rapid-removal method here; continuous therapy may be an alternative if haemodialysis is unavailable or poorly tolerated. D may be considered after a large, recent ingestion of slow-release lithium, not chronic accumulation without extra tablets. E attempts to increase renal clearance, but forced diuresis is not recommended and does not address her progressive neurological toxicity. ([medicines.org.uk](https://www.medicines.org.uk/emc/product/10828/smpc))

Reference: Lithium Carbonate Essential Pharma 250 mg film-coated tablets: Summary of Product Characteristics, section 4.9 (26 November 2024) — https://www.medicines.org.uk/emc/product/10828/smpc NHS Specialist Pharmacy Service: Lithium monitoring (6 December 2024) — https://sps.nhs.uk/monitorings/lithium-monitoring/ Extracorporeal Treatment for Lithium Poisoning: Systematic Review and Recommendations from the EXTRIP Workgroup (2015) — https://pubmed.ncbi.nlm.nih.gov/25583292/