Treatment of SIADH in Hyponatraemia with Severe Symptoms

Clinical Scenario

This protocol addresses patients with SIADH presenting with hyponatraemia and severe symptoms. When hyponatraemia causes severe symptoms, it reflects the presence of brain oedema — a situation requiring prompt, targeted first-hour intervention.

Treatment Approach (First Hour)

Regardless of whether the hyponatraemia is acute or chronic, the evidence-based approach in the first hour centres on prompt intravenous infusion of hypertonic saline, with serial serum sodium checks after each infusion cycle. Management should occur in a setting capable of close biochemical and clinical monitoring.

Specific infusion volumes, timing, repetition criteria, and the transition to cause-specific treatment are detailed in the full structured regimen.

Target: ≥ 5 mmol/l rise in serum sodium within the first hour

Instant Access to Structured Evidence-Based Regimens

References

DOI: 10.1530/EJE-13-1020

When hyponatraemia causes severe symptoms, it reflects the presence of brain oedema.

We recommend prompt i.v. infusion of 150 ml 3% hypertonic over 20 min (1D).

We suggest checking the serum sodium concentration after 20 min while repeating an infusion of 150 ml 3% hypertonic saline for the next 20 min (2D).

We suggest repeating therapeutic recommendations 7.1.1.1 and 7.1.1.2 twice or until a target of 5 mmol/l increase in serum sodium concentration is achieved (2D).

Manage patients with severely symptomatic hyponatraemia in an environment where close biochemical and clinical monitoring can be provided (not graded).

We recommend stopping the infusion of hypertonic saline (1D).

We recommend keeping the i.v. line open by infusing the smallest feasible volume of 0.9% saline until cause-specific treatment is started (1D).

Observational data and clinical experience indicate that a 5 mmol/l increase in serum sodium concentration can be sufficient to improve symptoms.

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