This protocol applies to patients with hyponatraemia (serum sodium <135 mmol/l) who are presenting with severe symptoms and whose initial acute treatment did not reach the expected sodium correction target.
Hyponatraemia (serum sodium <135 mmol/l) accompanied by one or more severe symptoms: vomiting, cardiorespiratory distress, abnormal and deep somnolence, seizures, or coma (Glasgow Coma Scale ≤ 8).
The initial approach — bolus infusions of 3% hypertonic saline repeated up to three times — targeted a 5 mmol/l rise in serum sodium within the first hour, with clinical improvement in symptoms.
When that target has not been reached, or symptoms have not improved, this continuing treatment protocol is the indicated next step.
Management continues with a sustained intravenous infusion of hypertonic saline, now guided by a defined incremental sodium correction goal per hour — with systematic monitoring at specified intervals and clear stopping criteria based on symptom status and total cumulative sodium change.
The full structured protocol — including specific thresholds, monitoring schedule, and stopping criteria — is available below.
Hyponatraemia, defined as a serum sodium concentration <135 mmol/l, is the most common disorder of body fluid and electrolyte balance encountered in clinical practice.
We define 'severely symptomatic' hyponatraemia as any biochemical degree of hyponatraemia in the presence of severe symptoms of hyponatraemia.
We recommend continuing an i.v. infusion of 3% hypertonic saline or equivalent aiming for an additional 1 mmol/l per h increase in serum sodium concentration (1D).
We recommend stopping the infusion of 3% hypertonic saline or equivalent when the symptoms improve, the serum sodium concentration increases 10 mmol/l in total or the serum sodium concentration reaches 130 mmol/l, whichever occurs first (1D).
We suggest checking the serum sodium concentration every 4 h as long as an i.v. infusion of 3% hypertonic saline or equivalent is continued (2D).