Hyperkalaemia Emergency Management
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Direct answer
Hyperkalaemia is a serum potassium above 5.5 mmol/L, becoming an emergency when ECG changes appear or the level climbs towards 6.5 mmol/L. Immediate treatment stabilises the myocardium with intravenous calcium gluconate, shifts potassium into cells with insulin and dextrose or nebulised salbutamol, then removes it with diuretics, potassium binders or dialysis. ECG changes guide urgency more than the number, and calcium's cardiac effect is temporary, so it may need repeating.
What you must remember
- Definition and pseudohyperkalaemia: serum potassium above 5.5 mmol/L; fist clenching, thrombocytosis, leucocytosis and delayed processing of the sample must be excluded.
- ECG progression: tall peaked T waves, then PR prolongation and loss of P waves, then QRS widening, a sine-wave pattern and finally ventricular fibrillation or asystole.
- Calcium gluconate: 10 per cent intravenously over several minutes stabilises the cardiac membrane within minutes and is repeated if ECG changes persist.
- Insulin and dextrose: regular insulin with glucose lowers potassium within about 15 to 30 minutes, with a reduced dose in renal failure because of hypoglycaemia risk, and glucose must be monitored for hours.
- Salbutamol: nebulised beta-2 agonist adds a rapid intracellular shift, with tachycardia as the main side effect.
- Elimination: loop diuretics in volume-replete patients, potassium binders such as sodium zirconium cyclosilicate or patiromer, and dialysis for refractory or oliguric cases.
- Common causes: renal failure, ACE inhibitors, ARBs, spironolactone, trimethoprim, heparin, rhabdomyolysis, tumour lysis, acidosis and digoxin toxicity.
A 68-year-old with CKD on ramipril and spironolactone
A 68-year-old man with chronic kidney disease, taking ramipril and spironolactone, presents with muscle weakness. His serum potassium is 7.1 mmol/L, and the ECG shows tall peaked T waves with a widened PR interval.
- Stabilise the myocardium: Give intravenous calcium gluconate with continuous ECG monitoring, stop ramipril and spironolactone, and confirm the sample is non-haemolysed.
- Shift potassium into cells: Insulin with dextrose is given, with a reduced insulin dose because of his renal function, and nebulised salbutamol is added for a rapid shift.
- Monitor for rebound: Glucose and potassium are checked hourly for several hours, because insulin's effect wanes and potassium can rebound.
- Remove potassium: Once the immediate danger has passed, a potassium binder is started and a loop diuretic is used if he is volume replete, with the drug dosing reviewed.
- Consider dialysis: If he is oliguric, anuric or refractory to medical therapy, dialysis is arranged. Sodium bicarbonate is reserved for patients who are also acidaemic, since its benefit in the absence of acidosis is limited.
Where the examiner tries to catch you
Four traps recur in hyperkalaemia questions.
- Trap: believing calcium lowers the potassium Correct: calcium stabilises the myocardium but does not change the serum level, which is why insulin and removal are still needed.
- Trap: treating the number instead of the ECG Correct: a potassium of 6.2 mmol/L with a normal ECG is managed differently from 6.8 mmol/L with QRS widening.
- Trap: believing insulin fixes the cause Correct: insulin moves potassium into cells rather than removing it, so it buys time, and stopping an ACE inhibitor or potassium-sparing diuretic is the lasting treatment.
- Trap: accepting a raised level with a normal ECG in a patient with a very high platelet count or a clenched fist Correct: this pattern points to a spurious result, so pseudohyperkalaemia must be excluded.
Frequently asked questions
What is the first drug given in hyperkalaemia with ECG changes?
Intravenous calcium gluconate is the first drug given in hyperkalaemia with ECG changes, because it stabilises the cardiac membrane within minutes. It does not lower the serum potassium, so insulin with dextrose and potassium removal are still required afterwards.
Why does insulin with glucose lower serum potassium?
Insulin with glucose lowers serum potassium by stimulating the sodium-potassium pump, which drives potassium into skeletal muscle and liver cells. Glucose is given with the insulin to prevent hypoglycaemia, and the effect is temporary, so glucose monitoring must continue for several hours.
Which ECG changes are seen in severe hyperkalaemia?
Severe hyperkalaemia produces a progression of ECG changes starting with tall peaked T waves, followed by PR prolongation, loss of P waves and QRS widening. The pattern can then develop into a sine-wave appearance, ventricular fibrillation or asystole, and any of these changes calls for immediate calcium.
Which potassium binder is used for chronic hyperkalaemia?
Sodium zirconium cyclosilicate and patiromer are used for chronic hyperkalaemia in patients who need renin-angiotensin blockade or mineralocorticoid antagonists to be continued. Older sodium polystyrene sulfonate is less favoured because of its slow onset and reports of intestinal injury.
When is dialysis indicated for severe hyperkalaemia?
Dialysis is indicated for severe hyperkalaemia that does not respond to medical therapy, or when the patient is oliguric or anuric with kidney failure and cannot excrete potassium. It is also used when potassium is rising despite treatment, because it removes potassium more reliably than binders or diuretics.