What are the management options for a patient with hyponatremia?

Management of Hyponatremia

Initial Assessment and Classification

Hyponatremia management begins with determining volume status (hypovolemic, euvolemic, or hypervolemic) and symptom severity, as these factors dictate treatment approach. 1

• Obtain serum and urine osmolality, urine sodium, and uric acid to establish the underlying cause 1
• Assess extracellular fluid volume status through physical examination, looking for orthostatic hypotension, dry mucous membranes (hypovolemia), or edema, ascites, and jugular venous distention (hypervolemia) 1
• Classify severity: mild (130-135 mmol/L), moderate (120-129 mmol/L), or severe (<120 mmol/L) 1
• Determine acuity: acute (<48 hours) versus chronic (>48 hours), as this impacts correction rate safety 1

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Seizures, Coma, Altered Mental Status)

For patients with severe symptoms, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until symptoms resolve. 1

• Give 100 mL boluses of 3% saline over 10 minutes, repeatable up to three times at 10-minute intervals until symptoms improve 1
• Never exceed 8 mmol/L total correction in 24 hours to prevent osmotic demyelination syndrome 1
• Monitor serum sodium every 2 hours during initial correction 1
• ICU admission is recommended for close monitoring 1

Asymptomatic or Mildly Symptomatic Hyponatremia

Treatment depends on volume status:

Treatment Based on Volume Status

Hypovolemic Hyponatremia

Discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion. 1

• Urinary sodium <30 mmol/L predicts good response to saline infusion (positive predictive value 71-100%) 1
• Initial infusion rate: 15-20 mL/kg/h, then 4-14 mL/kg/h based on response 1
• Common causes include gastrointestinal losses, diuretic use, and burns 1

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of treatment for SIADH. 1

• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• For resistant cases, consider vasopressin receptor antagonists (tolvaptan 15 mg once daily, titrate to 30-60 mg) 1, 2
• Alternative pharmacological options include urea, demeclocycline, or lithium 1
• Diagnostic criteria: euvolemia, urine sodium >20-40 mmol/L, urine osmolality >300 mOsm/kg, normal thyroid/adrenal function 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L. 1

• Temporarily discontinue diuretics if sodium <125 mmol/L 1
• For cirrhotic patients, consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it worsens ascites and edema 1
• Tolvaptan may be considered for persistent hyponatremia despite fluid restriction, but use with extreme caution in cirrhosis due to 10% risk of gastrointestinal bleeding (vs. 2% placebo) 2

Critical Correction Rate Guidelines

The maximum correction rate must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

• Standard correction rate: 4-8 mmol/L per day, not exceeding 10-12 mmol/L in 24 hours 1
• High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy) require even slower correction: 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours 1
• For severe symptoms: correct 6 mmol/L in first 6 hours, then only 2 mmol/L additional in next 18 hours 1
• Monitor sodium every 2 hours with severe symptoms, every 4 hours after symptom resolution 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours, immediately discontinue current fluids and switch to D5W (5% dextrose in water). 1

• Consider administering desmopressin to slow or reverse the rapid rise 1
• Target relowering to bring total 24-hour correction to no more than 8 mmol/L from starting point 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1

Special Considerations for Neurosurgical Patients

In neurosurgical patients, distinguish between SIADH and cerebral salt wasting (CSW), as they require opposite treatments. 1

• CSW requires volume and sodium replacement with isotonic or hypertonic saline, NOT fluid restriction 1
• For severe CSW symptoms, administer 3% hypertonic saline plus fludrocortisone (0.1-0.2 mg daily) in ICU 1
• In subarachnoid hemorrhage patients at risk of vasospasm, never use fluid restriction 1
• Consider hydrocortisone to prevent natriuresis in subarachnoid hemorrhage patients 1
• CSW characteristics: true hypovolemia with CVP <6 cm H₂O, urine sodium >20 mmol/L despite volume depletion 1

Common Pitfalls to Avoid

• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours—this causes osmotic demyelination syndrome 1
• Never use fluid restriction in cerebral salt wasting—this worsens outcomes 1
• Never use fluid restriction as initial treatment for altered mental status from hyponatremia—this is a medical emergency requiring hypertonic saline 1
• Inadequate monitoring during active correction increases risk of complications 1
• Failing to recognize and treat the underlying cause leads to poor outcomes 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms worsens edema and ascites 1
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant—even mild hyponatremia increases fall risk (21% vs. 5%) and mortality (60-fold increase with sodium <130 mmol/L) 1

Pharmacological Considerations

Vasopressin Receptor Antagonists (Vaptans)

Tolvaptan is FDA-approved for euvolemic or hypervolemic hyponatremia, starting at 15 mg once daily. 2

• Contraindicated with strong CYP3A inhibitors (ketoconazole increases tolvaptan AUC 5.4-fold) 2
• Avoid with moderate CYP3A inhibitors and grapefruit juice 2
• In cirrhosis, use with extreme caution due to higher gastrointestinal bleeding risk and increased all-cause mortality with long-term use 1
• Monitor closely to prevent overly rapid correction (>8 mmol/L/day) 2
• Common adverse effects: thirst (12%), dry mouth (7%), polyuria (11%) 2