Treatment of Hyponatremia with Hypovolaemia (Serum Sodium 120–135 mmol/L)
This protocol applies to patients with mild or moderate hyponatraemia — serum sodium in the range of 120–135 mmol/L — who also present with hypovolaemia. The co-occurrence of low serum sodium and intravascular volume depletion shapes both the clinical priority and the management approach.
Serum sodium 120–135 mmol/L (mild hyponatraemia: 131–135 mmol/L; moderate: 120–130 mmol/L) in the setting of hypovolaemia. Addressing the volume deficit is the immediate clinical priority in this presentation.
The approach centres on correcting the intravascular deficit with fluid replacement. The specific agent, monitoring requirements, and full clinical algorithm are detailed in the structured protocol — see below.
Sodium correction must proceed slowly. A critical safety target is a rise of no more than 8 mmol/L in any 24-hour period to avoid overcorrection and associated neurological complications.
HYPOnatraemia (Mild: 135–131 mmol/L, Moderate: 130–120 mmol/L, Severe: less than 120 mmol/L)
If hypovolaemic, correct intravascular deficit with 0.9% sodium chloride (see Guidelines for Prescribing Intravenous Fluids for Adults).
Correction should occur slowly – generally no more than 8 mmol/L in 24 hours.
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