ICU · Renal/Metabolic

Electrolyte disturbances in the ICU

Also known as Hyponatraemia and hypernatraemia · Hyperkalaemia and hypokalaemia · Hypocalcaemia and hypercalcaemia · Hypomagnesaemia · Hypophosphataemia and refeeding syndrome · SIADH vs cerebral salt wasting

Electrolyte disturbances are ubiquitous in ICU. Sodium: hyponatraemia (correct slowly — no more than 8 mmol/L in 24 h to avoid osmotic demyelination) vs hypernatraemia (free water deficit, correct at under 12 mmol/L per day). Potassium: hyperkalaemia (calcium gluconate for membrane stabilisation when there are ECG changes or K 6.5 mmol/L or over, insulin-dextrose for shift, then removal) vs hypokalaemia (correct Mg first or K will not correct). Calcium: ionised calcium is the relevant measure (not total or albumin-corrected calcium). Magnesium: essential cofactor — hypomagnesaemia causes refractory hypokalaemia and hypocalcaemia. Phosphate: hypophosphataemia in refeeding syndrome, sepsis, respiratory failure (diaphragm weakness). SIADH vs cerebral salt wasting: both cause hyponatraemia, but CSW has hypovolaemia (high urine Na + volume depletion) and requires salt + water, while SIADH is euvolaemic and needs fluid restriction.

Checked against its sources on 2 Sept 2026