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Electrolyte emergencies
Potassium, calcium and magnesium kill through the heart. Get an ECG, recognise the dangerous patterns, protect the heart, then correct the level at a safe rate and find the cause. Built for revision, not live patient decisions.
Settle them, and check the basics
ECG firstRed flags — what each should make you think
Treat the ECG, not just the number. A potassium of 6.8 with peaked T waves and a widening QRS is a peri-arrest emergency, while a potassium of 6.0 in a haemolysed sample may be nothing. Repeat a surprising result, but never delay calcium if the ECG is changing.
Hyperkalaemia — the three steps (UK Kidney Association)
- 1Protect the heart
- 2Shift potassium into cells
- 🩸Watch the glucose
- 3Remove potassium
- ECGCardiac monitor
- ☎Escalate
Understand the patient — the five you must know
levels, signs, causesPotassium
- High — AKI/CKD, ACEi/ARB, spironolactone, trimethoprim, NSAIDs, rhabdomyolysis, DKA, adrenal insufficiency, haemolysed sample. ECG: peaked T → flat P → wide QRS → sine wave → VF/asystole.
- Low — vomiting, diarrhoea, diuretics, insulin, salbutamol, refeeding, low magnesium. ECG: flat T, U waves, ST depression, long QT, arrhythmias.
Calcium (always use adjusted calcium)
- High — usually primary hyperparathyroidism or malignancy. "Bones, stones, groans, moans": pain, renal stones, constipation, confusion, polyuria, dehydration. Short QT.
- Low — post-thyroidectomy/parathyroidectomy, vitamin D deficiency, low magnesium, pancreatitis, CKD. Perioral tingling, cramps, Chvostek and Trousseau signs, tetany, seizures, long QT.
Magnesium & phosphate
- Low Mg — alcohol, PPIs, diuretics, diarrhoea. Causes refractory low K⁺ and low Ca²⁺, arrhythmias, torsades.
- Low phosphate — refeeding syndrome: weakness, respiratory failure, heart failure. Check before and during feeding in malnourished patients.
Work A–E — assess and act as you go
The diagnoses you must not miss
tap to open eachWhat points toward it, what would rule it in, and how to manage it.
Weakness, palpitations, or nothing at all. AKI, CKD, drugs, rhabdomyolysis, DKA.
Lab K⁺ (act on a blood gas if ECG changes); 12-lead ECG.
Calcium for the heart, insulin–glucose and salbutamol to shift, then remove (binders such as sodium zirconium cyclosilicate, treat cause, dialysis). Cardiac arrest: follow ALS with calcium and insulin–glucose.
Weakness, cramps, ileus, palpitations, U waves, arrhythmias.
K⁺, Mg, ECG.
IV potassium chloride in premixed bags — no more than 10 mmol/h via a peripheral line (faster only via central line with cardiac monitoring in HDU). Replace magnesium too, or the potassium won't stay up.
Confusion, vomiting, dehydration, AKI, abdominal pain, short QT; often known malignancy.
Adjusted calcium, PTH (high/normal = hyperparathyroidism; suppressed = malignancy), U&E, myeloma screen.
IV 0.9% saline (often 3–4 L over the first 24 h, watching for overload), then IV bisphosphonate once rehydrated. Treat the cause; oncology/endocrine.
Perioral tingling, carpopedal spasm, laryngospasm, seizures, long QT; recent neck surgery.
Adjusted Ca, Mg, PTH, vitamin D.
IV calcium gluconate 10% 10–20 mL over 10 min, then an infusion; replace magnesium. ECG monitoring.
Polymorphic VT with a twisting axis, long QT, low Mg/K, QT-prolonging drugs.
ECG, Mg, K.
IV magnesium sulfate 2 g over 10 min; correct potassium; stop QT-prolonging drugs; defibrillate if pulseless.
Investigate — what to order, when, and what it tells you
test with a question in mindECG
Repeat sample
Cause
Monitoring
How the plan comes together
disposition · handoverward
Corrected level, normal ECG, cause identified and addressed, plan for repeat bloods.
monitored bed / HDU
ECG changes, refractory levels, need for central potassium, ongoing infusion of calcium, or AKI needing dialysis.
Hand over: level and trend, ECG, what was given and when, next test due.
Look at the ECG, protect the heart, then fix the level slowly and find the cause. And remember magnesium: low potassium and low calcium won't correct until you replace it. Nicely done getting here.
Clerking template
copy or downloadElectrolyte emergencies — documentation structure
A structure and prompt list to help you document and think systematically. It is not a completeness check and cannot guarantee nothing is missed — use your trust's own proforma, your seniors, and your clinical judgement.
Test yourself
active recallCover the answer, say it out loud, then reveal. Retrieval beats re-reading.
0 / 12 knownFrequently asked questions
quick answersWhat are the red flags for electrolyte emergencies?
- K⁺ ≥6.5 or ECG changes — think severe hyperkalaemia
- Wide QRS, sine wave, bradycardia — think pre-arrest hyperkalaemia
- K⁺ below 2.5, weakness, arrhythmia — think severe hypokalaemia
- Adjusted Ca above 3.5, confused — think hypercalcaemic crisis
- Tetany, stridor, seizures, long QT — think severe hypocalcaemia
- Torsades de pointes — think low Mg / low K
- Very malnourished, starting to feed — think refeeding syndrome
What is the initial management of electrolyte emergencies?
- Protect the heart — calcium gluconate 10% 30 mL IV (or calcium chloride 10% 10 mL) if ECG changes; repeat if no effect
- Shift potassium into cells — 10 units soluble insulin with 25 g glucose IV; nebulised salbutamol 10–20 mg
- Watch the glucose — if pre-treatment glucose is below 7 mmol/L, follow with 10% glucose 50 mL/h for 5 h; hypoglycaemia is common for up to 6 h
- Remove potassium — treat the cause, potassium binder, stop culprit drugs; dialysis if refractory
- Cardiac monitor — repeat K⁺ at 1, 2, 4 and 6 h
- Escalate — refractory, very high, or with AKI → renal / ITU
Always alongside senior support and your local guideline.
What diagnoses must you not miss in electrolyte emergencies?
- Severe hyperkalaemia — K⁺ ≥6.5 · ECG changes
- Severe hypokalaemia — K⁺ below 2.5 · arrhythmia
- Hypercalcaemic crisis — adj Ca above 3.5
- Severe hypocalcaemia — tetany · seizures · long QT
- Torsades de pointes — long QT · low Mg
Open each one in the must-not-miss section for what points toward it, how to rule it in, and how to manage it.
What investigations should a junior doctor order for electrolyte emergencies?
- ECG — Danger level more than the number.
- Repeat sample — Haemolysis, delayed processing, high platelets/WBC give false highs.
- Cause — Renal function, acidosis.
- Monitoring — 1, 2, 4 and 6 h after treatment.
Admit or discharge: how is the plan decided for electrolyte emergencies?
- Ward — Corrected level, normal ECG, cause identified and addressed, plan for repeat bloods.
- Monitored bed / hdu — ECG changes, refractory levels, need for central potassium, ongoing infusion of calcium, or AKI needing dialysis.
Is there a clerking template for electrolyte emergencies?
Yes — there is a free clerking template for electrolyte emergencies on this page, structured as presenting complaint, red flags asked, history, examination (A–E), investigations, differentials, plan and escalation. You can copy it or download it as a Word document. Jump to the template.
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