Sodium Chloride 3% (Hypertonic Saline)

How it works

By raising plasma osmolality it draws water out of cells, including cerebral tissue, increasing serum sodium and reducing intracranial volume and pressure.

Prescribing in practice

• Overly rapid correction of chronic hyponatraemia risks osmotic demyelination syndrome, so the rate of rise of serum sodium must be tightly controlled and frequently rechecked.
• This is a hypertonic, potentially vesicant solution that is preferably given through a central line, as extravasation can cause tissue damage.
• Use with caution in fluid overload, heart failure, and renal impairment because of the added sodium and volume load.

Monitoring

Check serum sodium and osmolality frequently during infusion to ensure the rate of correction stays within safe limits and to avoid overcorrection.

Counselling the patient

• Explain to the team that serum sodium will be measured regularly and the infusion rate adjusted accordingly.
• Highlight that concentrated saline should ideally run via central access and the site be watched for extravasation.
• Note that neurological status should be monitored as part of assessing response and safety.

Evidence & guidelines

Hypertonic saline is a standard option for severe symptomatic hyponatraemia and raised intracranial pressure, with controlled correction rates supported by UK and European consensus guidance.