Synopsis
Treat cerebral symptoms immediately, classify hypotonic hyponatraemia physiologically and prevent osmotic injury from uncontrolled sodium correction.
- Base emergency treatment on neurological symptoms and their likely relation to hyponatraemia, not on the sodium concentration alone; profound chronic hyponatraemia may be asymptomatic while a rapid moderate fall can cause cerebral oedema.
- Confirm tonicity: hyperglycaemia causes translocational hyponatraemia, and very high lipid or protein can create measurement artefact with some laboratory methods.
- For severe or moderately severe symptoms, the Society for Endocrinology recommends 150 mL of 3% sodium chloride over 20 minutes, repeated according to the measured response in a suitable monitored environment.
Key red flags
Seizure, cardiorespiratory arrest, persistent vomiting, coma or Glasgow Coma Scale at or below eight defines the highest emergency category in Society guidance.
Investigation priorities
Confirm the value and measure correction without inter-method variation obscuring small but important changes.
Management branches
Hyponatraemia accompanies severe or moderately severe neurological symptoms without a more convincing immediate explanation.
- Use ABCDE, bedside glucose and seizure care, call an experienced senior clinician and transfer to an environment able to deliver hypertonic saline with rapid sodium measurement.
- Give 150 mL 3% sodium chloride or locally equivalent hypertonic solution over 20 minutes, remeasure sodium using the same platform and repeat as the Society algorithm directs towards a 5 mmol/L first-hour rise.
Key medicines
Hypertonic sodium chloride 3%For severe or moderately severely symptomatic adult hyponatraemia, Society for Endocrinology guidance uses 150 mL intravenously over 20 minutes, rechecking sodium and repeating up to the algorithm limit to achieve about a 5 mmol/L first-hour rise.