What is the treatment for hyponatremia?

Treatment of Hyponatremia

The treatment of hyponatremia depends critically on symptom severity, volume status, and rapidity of onset, with severe symptomatic cases requiring immediate 3% hypertonic saline to correct 6 mmol/L over 6 hours while never exceeding 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome. 1, 2

Initial Assessment and Classification

Before initiating treatment, determine three key factors:

• Symptom severity: Severe symptoms include seizures, coma, altered mental status, or respiratory distress requiring immediate intervention 1, 2, 3
• Volume status: Assess for hypovolemia (orthostatic hypotension, dry mucous membranes, decreased skin turgor), euvolemia, or hypervolemia (edema, ascites, jugular venous distention) 1, 2, 4
• Chronicity: Acute (<48 hours) vs. chronic (>48 hours) onset, as chronic cases require slower correction 1, 2, 5

Obtain serum and urine osmolality, urine sodium, urine electrolytes, and serum uric acid to determine the underlying cause 1, 2. A serum sodium <131 mmol/L warrants full diagnostic workup 1, 2.

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

For patients with seizures, coma, altered consciousness, or severe neurological symptoms:

• Administer 3% hypertonic saline immediately with a goal to increase sodium by 6 mmol/L over 6 hours or until severe symptoms resolve 1, 2, 3
• Total correction must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2, 5
• Hypertonic saline can be given as 100-150 mL boluses over 10 minutes, repeated up to three times at 10-minute intervals until symptoms improve 2, 6
• Transfer to ICU for close monitoring with serum sodium checks every 2 hours during initial correction 1, 2
• Calculate sodium deficit: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 2

Mild to Moderate Symptomatic or Asymptomatic Hyponatremia

Treatment depends on volume status:

Treatment Based on Volume Status

Hypovolemic Hyponatremia

Characterized by urine sodium <30 mmol/L, signs of volume depletion:

• Discontinue diuretics immediately 2, 7
• Administer isotonic saline (0.9% NaCl) for volume repletion at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on response 2, 7
• Urine sodium <30 mmol/L predicts 71-100% response to saline infusion 2
• Once euvolemic, reassess and adjust treatment based on underlying cause 2

Euvolemic Hyponatremia (SIADH)

Characterized by urine sodium >20-40 mmol/L, urine osmolality >300-500 mOsm/kg, normal volume status:

• Fluid restriction to 1 L/day is the cornerstone of first-line treatment 1, 2, 8, 3
• If no response to fluid restriction after 24-48 hours, add oral sodium chloride 100 mEq three times daily 2, 8
• For persistent cases despite fluid restriction, consider:
  • Urea (effective second-line option, though poorly palatable) 2, 3, 6
  • Tolvaptan 15 mg once daily, titrated to 30-60 mg as needed 2, 9
  • Demeclocycline, lithium, or loop diuretics (less commonly used) 1, 2, 8
• Monitor serum sodium every 4 hours initially, then daily 2, 8

Important distinction in neurosurgical patients: Cerebral salt wasting (CSW) mimics SIADH but requires opposite treatment—volume and sodium replacement, NOT fluid restriction 1, 2. CSW is characterized by true hypovolemia with high urine sodium despite volume depletion 2.

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Characterized by edema, ascites, elevated jugular venous pressure:

• Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 2, 3, 4, 7
• Temporarily discontinue diuretics if sodium <125 mmol/L 2
• In cirrhotic patients, consider albumin infusion alongside fluid restriction 2, 3
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens fluid overload 2
• For persistent hyponatremia despite fluid restriction and maximized medical therapy, consider tolvaptan 15 mg daily with extreme caution in cirrhosis due to increased gastrointestinal bleeding risk (10% vs 2% placebo) 2, 9
• Sodium restriction (2-2.5 g/day) is more effective than fluid restriction for weight loss, as fluid follows sodium 2

Critical Correction Rate Guidelines

Standard correction limits to prevent osmotic demyelination syndrome:

• Maximum 8 mmol/L correction in 24 hours for average-risk patients 1, 2, 3, 5
• Maximum 4-6 mmol/L per day for high-risk patients: advanced liver disease, alcoholism, malnutrition, prior encephalopathy, severe hyponatremia (<120 mmol/L) 1, 2, 3
• For severe symptoms: correct 6 mmol/L in first 6 hours, then limit additional correction to 2 mmol/L over next 18 hours 1, 2
• Chronic hyponatremia (>48 hours) should not be corrected faster than 1 mmol/L/hour 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) 2
• Consider administering desmopressin to slow or reverse the rapid rise 2
• Monitor for osmotic demyelination syndrome signs: dysarthria, dysphagia, oculomotor dysfunction, quadriparesis (typically 2-7 days after rapid correction) 2

Special Populations and Considerations

Neurosurgical Patients

• Distinguish between SIADH and cerebral salt wasting (CSW) as treatments are opposite 1, 2
• CSW requires volume and sodium replacement with isotonic or hypertonic saline, plus fludrocortisone for severe cases 1, 2
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1, 2
• Consider hydrocortisone to prevent natriuresis in SAH patients 1, 2

Cirrhotic Patients

• Hyponatremia increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 2
• Require more cautious correction (4-6 mmol/L per day) due to higher osmotic demyelination risk 2
• Tolvaptan carries 10% gastrointestinal bleeding risk vs 2% with placebo 2, 9

Common Pitfalls to Avoid

• Never ignore mild hyponatremia (130-135 mmol/L): associated with 60-fold increased mortality (11.2% vs 0.19%), increased falls (21% vs 5%), and cognitive impairment 2, 10, 3
• Never use fluid restriction in cerebral salt wasting—this worsens outcomes 1, 2
• Never exceed 8 mmol/L correction in 24 hours to avoid osmotic demyelination syndrome 1, 2, 3
• Never use normal saline for SIADH or hypervolemic hyponatremia—it can worsen hyponatremia 2, 7
• Never obtain ADH or natriuretic peptide levels—not supported by evidence and delays treatment 1, 2
• Inadequate monitoring during active correction leads to overcorrection complications 2