Management of Hyponatraemia

1. Symptom severity

Mild: lethargy, anorexia (see flow chart 1)

Moderate: Nausea, confusion, headache (review absolute level and duration, see flowchart 2)

Severe: Seizures, drowsiness, coma, respiratory arrest (reflecting cerebral oedema). This is an emergency requiring prompt senior input, see flow chart 2 and consider management in a critical care setting.

2. Duration/acuity

Acute <48 hours duration - greater risk of complications of cerebral oedema

Chronic >48 hours duration - greater risk from overaggressive therapy

3. Absolute serum sodium level

Mild: 130-133 mmol/L (does not require investigation)

Moderate: 125-129 mmol/L (if mild or no symptoms, investigation as in flow chart 1)

Profound: <125 mmol/L (particular risk of cerebral oedema <120 mmol/L) requires urgent investigation and treatment, depending on symptom severity (see flowchart 2).

N.B. In view of particular clinical risk around patients with serum sodium <120mmol/L, a clinical biochemist will usually phone this result through to aid with time-critical management.