Severe hyperkalaemia with ECG changes — MRCEM SBA MCQ

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EasyResuscitation and critical illnessSevere hyperkalaemia with ECG changesMRCEM SBA

A 64-year-old man receiving maintenance haemodialysis attends the emergency department after missing a dialysis session. He feels weak but is alert, breathing adequately and has a palpable pulse. A non-haemolysed laboratory sample confirms a potassium concentration of 7.2 mmol/L; capillary blood glucose is 8.1 mmol/L. His ECG shows new broad QRS complexes and peaked T waves. Cardiac monitoring and large-bore intravenous access are established. Which immediate treatment sequence is most appropriate?

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Correct answer: C — Give 30 mL of 10% calcium gluconate, then intravenous insulin with glucose.

The confirmed potassium concentration is in the severe range, and the new QRS widening indicates cardiac toxicity. Protect the myocardium immediately with **30 mL of 10% calcium gluconate intravenously over 10 minutes**, then promptly give insulin with glucose to shift potassium into cells. Continue ECG monitoring, reassess for persistent ECG changes, and arrange urgent renal review: calcium’s effect is temporary and it does not remove potassium. Haemodialysis may provide definitive potassium removal for this patient, but arranging it must not postpone initial cardiac protection. ([gov.uk](https://www.gov.uk/drug-safety-update/calcium-chloride-calcium-gluconate-potential-risk-of-underdosing-with-calcium-gluconate-in-severe-hyperkalaemia)) **A** offers an effective potassium-shifting treatment but reverses the priority when ECG toxicity is already present; insulin–glucose would be appropriate without preceding calcium if immediate cardiac protection were not indicated. **B** gets the sequence right but gives an inadequate calcium-gluconate dose; 10 mL of *10% calcium chloride*, not calcium gluconate, provides approximately the recommended equivalent calcium dose. **D** recognises the likely need for dialysis but delays myocardial stabilisation; dialysis becomes the priority for potassium removal after emergency stabilisation has begun. **E** uses two potassium-shifting treatments while omitting immediate calcium; nebulised salbutamol can be an adjunct, but is not a substitute for cardiac protection in this presentation. ([gov.uk](https://www.gov.uk/drug-safety-update/calcium-chloride-calcium-gluconate-potential-risk-of-underdosing-with-calcium-gluconate-in-severe-hyperkalaemia))

Reference: Calcium chloride, calcium gluconate: potential risk of underdosing with calcium gluconate in severe hyperkalaemia (27 June 2023) — https://www.gov.uk/drug-safety-update/calcium-chloride-calcium-gluconate-potential-risk-of-underdosing-with-calcium-gluconate-in-severe-hyperkalaemia A Clinical Guideline for the Management of Hyperkalaemia in Adults (Approved 20 August 2024) — https://www.nnuh.nhs.uk/publication/download/hyperkalaemia-in-adults-jcg0020-v6/