Protect the heart, shift it in, then remove it
Expansion
Three steps, in order
- Protect the heart: calcium gluconate 10 per cent, 10 to 30 ml, if there are ECG changes. Onset in minutes, lasts 30 to 60, and does not lower the potassium
- Shift it into cells: 10 units of insulin in 25 g of glucose, plus nebulised salbutamol. Onset 15 to 30 minutes
- Remove it: dialysis if refractory or in renal failure, potassium binders (patiromer, sodium zirconium) for slower removal, and treat the cause
“Calcium buys time; insulin buys hours; only dialysis removes it.”
ECG changes in order of severity: tall tented T waves, then flattened P waves and a prolonged PR, then a broad QRS, then a sinusoidal wave and cardiac arrest. Changes do not correlate reliably with the level, so treat the ECG.
Severity: mild 5.5 to 5.9, moderate 6.0 to 6.4, severe 6.5 or above, and any level with ECG changes is treated as severe.
Causes: renal failure, drugs (ACE inhibitors, ARBs, spironolactone, NSAIDs, trimethoprim, heparin), acidosis, rhabdomyolysis and tumour lysis, Addison’s disease, and massive transfusion.
Exclude a spurious result from haemolysis, a tight tourniquet, fist clenching, delayed processing or a very high platelet or white cell count, but never delay treatment in a patient with ECG changes.