How to manage a patient with persistent hyponatremia?

Management of Persistent Hyponatremia

For a patient with persistent hyponatremia, immediately reassess volume status and symptom severity to determine if the current treatment approach is appropriate, then adjust therapy based on the underlying etiology—switching from normal saline to fluid restriction for SIADH, or escalating to hypertonic saline for severe symptoms, while ensuring sodium correction never exceeds 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Reassessment of Persistent Hyponatremia

When hyponatremia persists despite initial treatment, the first critical step is determining whether the diagnosis and treatment approach are correct 1:

• Verify volume status clinically: Look for orthostatic hypotension, dry mucous membranes, decreased skin turgor (hypovolemia) versus peripheral edema, ascites, jugular venous distention (hypervolemia) versus absence of both (euvolemia) 1
• Check urine sodium and osmolality: Urine sodium <30 mmol/L suggests hypovolemic hyponatremia responsive to saline, while >20-40 mmol/L with urine osmolality >300 mOsm/kg suggests SIADH 1
• Assess symptom severity: Severe symptoms (seizures, coma, altered mental status) require immediate hypertonic saline regardless of chronicity 1

A common pitfall is continuing normal saline in a patient with SIADH, which will worsen hyponatremia through dilution 1. Conversely, using fluid restriction in cerebral salt wasting can be catastrophic 1.

Management Algorithm Based on Volume Status

For Hypovolemic Hyponatremia (Worsening on Normal Saline)

• Continue isotonic saline (0.9% NaCl) for volume repletion at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on response 1
• Discontinue diuretics immediately if sodium <125 mmol/L 1
• Consider albumin infusion in cirrhotic patients alongside saline 1
• Maximum correction rate: 8 mmol/L per 24 hours; for high-risk patients (cirrhosis, alcoholism, malnutrition), limit to 4-6 mmol/L per day 1

For Euvolemic Hyponatremia (SIADH)

If the patient is on normal saline and worsening, immediately discontinue normal saline and switch to 1:

• Fluid restriction to 1 L/day as first-line therapy 1
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction alone 1
• For severe symptoms: Administer 3% hypertonic saline with goal of 6 mmol/L correction over 6 hours or until symptoms resolve, maximum 8 mmol/L in 24 hours 1
• Second-line pharmacological options for refractory cases:
  • Tolvaptan 15 mg once daily, titrate to 30-60 mg (must initiate in hospital with close sodium monitoring) 2
  • Urea 15-30 g/day in divided doses 1
  • Demeclocycline or lithium (less commonly used due to side effects) 1

Critical warning: Tolvaptan must be initiated in hospital because too rapid correction (>12 mEq/L/24 hours) can cause osmotic demyelination syndrome 2. In cirrhotic patients, tolvaptan carries a 10% risk of gastrointestinal bleeding versus 2% with placebo 1, 2.

For Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
• Temporarily discontinue diuretics until sodium improves 1
• In cirrhosis: Consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens ascites and edema 1
• Sodium restriction (not fluid restriction) results in weight loss as fluid follows sodium in cirrhotic patients 1
• For refractory cases: Consider tolvaptan only after maximizing guideline-directed medical therapy and fluid restriction, with extreme caution in cirrhosis 1, 2

Special Consideration: Distinguishing SIADH from Cerebral Salt Wasting

In neurosurgical patients or those with CNS pathology, this distinction is critical because treatments are opposite 1:

SIADH characteristics 1:

• Euvolemic state (no edema, normal blood pressure, normal skin turgor)
• Urine sodium >20-40 mmol/L
• Urine osmolality >300 mOsm/kg
• Treatment: Fluid restriction

Cerebral Salt Wasting characteristics 1:

• True hypovolemia (orthostatic hypotension, tachycardia, dry mucous membranes)
• Urine sodium >20 mmol/L despite volume depletion
• Central venous pressure <6 cm H₂O
• Treatment: Volume and sodium replacement with normal saline or hypertonic saline, plus fludrocortisone 0.1-0.2 mg daily for severe cases 1

Never use fluid restriction in cerebral salt wasting—this worsens outcomes 1.

Critical Safety Considerations

Correction Rate Limits (Preventing Osmotic Demyelination Syndrome)

• Standard patients: Maximum 8 mmol/L per 24 hours 1
• High-risk patients (advanced liver disease, alcoholism, malnutrition, severe hyponatremia): Maximum 4-6 mmol/L per day 1
• For severe symptoms: Correct 6 mmol/L over first 6 hours or until symptoms resolve, then slow correction to stay within 8 mmol/L total for 24 hours 1

Monitoring Requirements

• Severe symptoms: Check sodium every 2 hours during initial correction 1
• Mild symptoms: Check sodium every 4 hours initially, then every 6-12 hours 1
• Watch for osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically 2-7 days after rapid correction 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours 1:

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water)
• Consider desmopressin to slow or reverse the rapid rise
• Target relowering to bring total 24-hour correction to ≤8 mmol/L from starting point

Common Pitfalls to Avoid

• Using normal saline in SIADH: This worsens hyponatremia through dilution 1
• Using fluid restriction in cerebral salt wasting: This is catastrophic and worsens outcomes 1
• Ignoring mild hyponatremia (130-135 mmol/L): Even mild hyponatremia increases fall risk (21% vs 5%) and mortality (60-fold increase with sodium <130 mmol/L) 1, 3
• Overly rapid correction: Exceeding 8 mmol/L in 24 hours risks osmotic demyelination syndrome 1, 2
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms: This worsens edema and ascites 1
• Inadequate monitoring during active correction: Check sodium frequently to prevent overcorrection 1