Potassium disorders
Potassium disorders are common and potentially life‑threatening presentations in the emergency department. Both hyperkalaemia and hypokalaemia can cause neuromuscular dysfunction and cardiac arrhythmia; prompt recognition, ECG‑guided risk stratification and rapid institution of appropriate therapy are essential.
Overview
- Normal adult serum potassium ~3.5-5.0 mmol/L (laboratory ranges vary). Small changes in extracellular K+ have large effects on resting membrane potential and cardiac conduction.
- Emergency management focuses on: (1) recognising the problem with early ECG, (2) stabilising the myocardium if threatened, (3) temporising by shifting K+ into cells, and (4) definitive removal or replacement depending on cause.
- Follow local Trust protocols and Resuscitation Council UK guidance for resuscitation‑era dosing and paediatric weight‑based regimens (Resuscitation Council UK 2025).
Physiology - points relevant to acute care
- Total body K+ ≈ 50-75 mmol/kg; >98% is intracellular. Serum K+ reflects only a small fraction of total stores.
- Daily intake ~50-100 mmol; the kidney is the principal route of elimination and is regulated by aldosterone and distal nephron factors.
- Rapid shifts between intra‑ and extracellular compartments occur with insulin, β2‑agonists, acid-base disturbances, and cell breakdown (tumour lysis, rhabdomyolysis).
- Magnesium deficiency impairs renal K+ repletion and must be corrected when present.