Emergency Medicine Emergency Medicine · High Yield

Hyperkalaemia Causes

Hyperkalaemia (K+ >5.5 mmol/L) is potentially fatal due to cardiac arrhythmias. Urgent treatment is required when K+ >6.5 mmol/L or ECG changes are present.

✦ The Mnemonic

"DR CRAMP — Hyperkalaemia Causes"

Drugs · Renal failure · Crush · RTA · Addison's · Massive transfusion · Pseudohyperkalaemia

D Drugs ACEi, ARBs, K+-sparing diuretics, NSAIDs, trimethoprim, digoxin overdose, heparin

R Renal failure Most common clinical cause — reduced K+ excretion; any cause of AKI or CKD

C Crush injury / Cell lysis Rhabdomyolysis, haemolysis, tumour lysis syndrome — massive K+ release

R RTA type IV Renal tubular acidosis — aldosterone deficiency or resistance; hyperkalaemia + metabolic acidosis

A Addison's disease Aldosterone deficiency → K+ retention + Na+ loss; hyponatraemia + hyperkalaemia

M Massive blood transfusion Stored blood leaks K+ — relevant in trauma resuscitation

P Pseudohyperkalaemia Haemolysed sample, delayed processing, thrombocytosis, leukocytosis — check a fresh sample

📚 Clinical Breakdown

ECG changes in hyperkalaemia (in order of severity): peaked T waves → PR prolongation → P wave flattening → widened QRS → sine wave pattern → VF/asystole. Any ECG change requires immediate treatment with IV calcium gluconate (membrane stabilisation).

Emergency treatment: 1) IV calcium gluconate 10 mL 10% (membrane stabilisation — works in minutes); 2) Insulin + glucose (drives K+ into cells — works in 30 min); 3) Salbutamol nebulised (also drives K+ intracellular); 4) Sodium bicarbonate if acidotic; 5) Calcium resonium or patiromer (removes K+ from gut — hours); 6) Haemodialysis if refractory.

Pseudohyperkalaemia: always exclude before treating. A haemolysed sample (visible pink colour), delayed processing, or extreme thrombocytosis/leukocytosis can falsely raise K+. Request a fresh sample in a lithium heparin tube, processed immediately.

Immediate treatment IV calcium gluconate — membrane stabilisation

Drives K+ into cells Insulin + glucose + salbutamol

Removes K+ from body Resonium, patiromer, haemodialysis

ECG first change Tall peaked T waves

⭐ Clinical Pearl

Hyperkalaemia in AKI + ACEi: the most common preventable cause in hospital. Stop ACEi/ARBs + K+-sparing diuretics immediately. Review all medications. Correct volume depletion. If K+ >6.5 mmol/L and not responding to medical management within 2–4 hours — request urgent nephrology review for haemodialysis.

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