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EM SAQsElectrolyte emergencies — potassium and sodium

EM SAQs · Electrolyte emergencies — potassium and sodium

Hyperkalaemia ladder and acute hyponatraemic seizure

ACEM-style SAQ covering hyperkalaemia membrane stabilisation/shift/removal and hypertonic saline for acute hyponatraemia.

10 marks10 min1 min readSource-verified ·

Target exams

ACEMFRCEMABEM
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Study tools

Target exams

ACEMFRCEMABEM
Prompt
Part A: A 68-year-old man with AKI has K 7.4 mmol/L, peaked T waves and QRS 140 ms. Detail your immediate treatment ladder with drug doses and what each step achieves. Part B: A 28-year-old with a three-day water binge seizes; Na 112 mmol/L. Detail acute management and the chronic-correction limit that prevents osmotic demyelination. (10 marks)

Model answer

Reveal model answerShowHide

Part A — ECG-unstable hyperkalaemia. Treat immediately; calcium is first because the ECG shows cardiotoxicity.[1][2]

  1. Membrane stabilisation (does not lower K): calcium chloride 10 mL of 10% IV over 2–5 minutes (or calcium gluconate 30 mL of 10% IV). Protects the heart within minutes; re-dose if QRS remains wide.[1][2]
  2. Intracellular shift (temporary): soluble insulin 10 units IV with 50 mL of 50% dextrose (monitor glucose); nebulised salbutamol 10–20 mg; consider sodium bicarbonate IV if significantly acidotic and ventilating adequately.
  3. Removal (definitive): enhance excretion / remove K — loop diuretic if residual renal function and volume allows; potassium binders (e.g. sodium zirconium cyclosilicate / patiromer per availability); urgent dialysis for refractory hyperK, anuria, severe AKI, or ongoing tissue release.
  4. Continuous monitoring; treat cause (AKI, drugs, rhabdo); repeat ECG and K.

Part B — acute symptomatic hyponatraemia with seizure. This is cerebral oedema physiology. Give 3% hypertonic saline 100 mL IV bolus over ~10 minutes; repeat every 10 minutes up to three doses if seizures continue, aiming for a small controlled rise in Na (4–6 mmol/L) sufficient to stop seizures. Then slower correction. For chronic hyponatraemia, limit correction typically to ≤8 mmol/L in 24 hours (stricter limits in high osmotic-demyelination risk: alcoholism, malnutrition, liver disease) with frequent Na checks. Do not use fluid restriction alone in a seizing patient — hypertonic saline is the treatment.[1]

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References2ShowHide
  1. [1]Geldermann N, Dzimiera J, Fischer H, et al. Acute hyperkalaemia in emergency care: evidence-based approaches. Emergency Medicine Journal, 2026.PMID 41506858
  2. [2]Lemoine L, Le Bastard Q, Batard E, et al. An evidence-based narrative review of the emergency department management of acute hyperkalaemia. The Journal of Emergency Medicine, 2021.PMID 33423833
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