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Severe hyperkalaemia with ECG changes — MRCEM SBA MCQ

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EasyCardiovascular emergenciesSevere hyperkalaemia with ECG changesMRCEM SBA

A 69-year-old man presents with weakness and reduced urine output after three days of vomiting. He is alert, with a blood pressure of 116/70 mmHg. His ECG shows new peaked T waves and QRS widening to 140 ms. A non-haemolysed laboratory sample confirms potassium 7.1 mmol/L; creatinine is 264 micromol/L, compared with 105 micromol/L last month. He does not take digoxin. Cardiac monitoring and reliable intravenous access are established. Which initial treatment and disposition plan is most appropriate?

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

Reveal the answer and explanation

Correct answer: A — Give 30 mL of 10% calcium gluconate IV over 10 minutes, then insulin–glucose; arrange monitored admission and renal review.

The confirmed potassium of 7.1 mmol/L is severe hyperkalaemia, and the new peaked T waves and widened QRS show myocardial toxicity. The immediate priority is to stabilise the myocardium with an adequate dose of intravenous calcium. Thirty millilitres of 10% calcium gluconate over 10 minutes provides the recommended calcium dose; insulin–glucose must follow promptly because calcium does not lower serum potassium. Repeat the ECG, continue cardiac and biochemical monitoring, and arrange admission with renal review given the associated acute kidney injury. Further calcium may be needed if ECG abnormalities persist. ([gov.uk](https://www.gov.uk/drug-safety-update/calcium-chloride-calcium-gluconate-potential-risk-of-underdosing-with-calcium-gluconate-in-severe-hyperkalaemia)) B offers effective potassium-shifting treatments but omits immediate cardiac stabilisation. C selects the right calcium salt but gives just one-third of the recommended initial volume, a recognised underdosing risk. D likewise delays calcium; salbutamol is an adjunct, not a substitute for myocardial protection. E offers a means of removing potassium, but an oral binder cannot replace immediate calcium and insulin–glucose when ECG toxicity is present. The acceptable blood pressure does not make these ECG changes safe to observe. ([doclibrary-rcht.cornwall.nhs.uk](https://doclibrary-rcht.cornwall.nhs.uk/DocumentsLibrary/RoyalCornwallHospitalsTrust/Clinical/Renal/AdultHyperkalaemiaManagementClinicalGuideline.pdf))

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 Adult Hyperkalaemia Management Clinical Guideline, version 7.0 (December 2025) — https://doclibrary-rcht.cornwall.nhs.uk/DocumentsLibrary/RoyalCornwallHospitalsTrust/Clinical/Renal/AdultHyperkalaemiaManagementClinicalGuideline.pdf