Clinical Scenario

This protocol addresses patients with acute hyponatraemia confirmed to have developed within 48 hours, presenting with a serum sodium concentration below 135 mmol/l in the absence of severe or moderately severe symptoms.

Acute hyponatraemia is defined as hyponatraemia documented to exist under 48 hours — a distinction that directly shapes the urgency and goals of management.

Management Approach

The cornerstone of management is identifying and treating the underlying cause. Where feasible, fluids, medications, and other factors that may be contributing to or provoking the sodium drop should be addressed. If the acute decrease in serum sodium is significant, a specific intravenous intervention may be warranted, followed by reassessment of serum sodium concentration to inform next steps.

Full sequencing, intervention criteria, and monitoring guidance are in the complete protocol.

References

We define 'acute' hyponatraemia as hyponatraemia that is documented to exist <48 h.
We recommend cause-specific treatment (1D).
If the acute decrease in serum sodium concentration exceeds 10 mmol/l, we suggest a single i.v. infusion of 150 ml 3% hypertonic saline or equivalent over 20 min (2D).

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Treatment of Acute Hyponatraemia Documented Under 48 Hours with Serum Sodium Below 135 mmol/l

References