Syndrome of inappropriate antidiuretic hormone secretion
ICD-10 E22.2 · ICD-11 5A60.2

SIADH with Moderately Severe Hyponatraemia — When Initial Treatment Has Not Achieved the Sodium Target

In SIADH presenting with moderately severe symptoms, the first treatment step targets a defined rise in serum sodium. When that target is not met and symptoms persist, a specific next-line protocol applies.

Previous line — target not achieved

The initial protocol — which included stopping medications contributing to hyponatraemia, cause-specific treatment, and a single i.v. infusion of hypertonic saline — did not achieve the goal of a 5 mmol/l per 24-hour increase in serum sodium concentration with improvement of symptoms.

Clinical scenario

Hyponatraemia with moderately severe symptoms is a dangerous condition. This protocol addresses the situation where those symptoms remain unresolved and the sodium correction threshold was not reached with the initial single-infusion approach.

Next-line approach (partial overview)

Management escalates to the approach used in severely symptomatic hyponatraemia, involving repeated i.v. hypertonic saline infusions in a setting that allows close biochemical and clinical monitoring — the full repetition criteria, monitoring schedule, and stopping rules are contained in the complete protocol.

Treatment target

A 5 mmol/l increase in serum sodium concentration with improvement of symptoms.

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References

DOI: 10.1530/EJE-13-1020

Hyponatraemia with moderately severe symptoms is a dangerous condition.

We suggest considering to manage the patient as in severely symptomatic hyponatraemia if the serum sodium concentration further decreases despite treating the underlying diagnosis (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).

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