What is the treatment for hyponatremia (low sodium)?

Treatment for Hyponatremia

The treatment of hyponatremia depends critically on three factors: symptom severity, volume status (hypovolemic, euvolemic, or hypervolemic), and chronicity, with the overriding principle being to never exceed correction of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Immediate Assessment Required

Before initiating treatment, you must determine:

• Symptom severity: Severe symptoms (seizures, coma, altered mental status) versus mild symptoms (nausea, headache) versus asymptomatic 1, 2
• Volume status: Assess for signs of hypovolemia (orthostatic hypotension, dry mucous membranes), euvolemia, or hypervolemia (edema, ascites, jugular venous distention) 1
• Chronicity: Acute (<48 hours) versus chronic (>48 hours) - this determines safe correction rates 1
• Serum and urine osmolality, urine sodium: Essential for determining etiology 1

Treatment Based on Symptom Severity

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

This is a medical emergency requiring immediate hypertonic saline, not fluid restriction. 1

• Administer 3% hypertonic saline immediately with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve 1, 3
• Total correction must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 4
• 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

• Urine sodium <30 mmol/L predicts good response to saline infusion (positive predictive value 71-100%) 1
• Once euvolemic, reassess and treat based on underlying cause 1
• Correction rate should not exceed 8 mmol/L in 24 hours 1

Euvolemic Hyponatremia (SIADH)

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

• Initial approach: Restrict fluids to 1000 mL/day 1
• If no response to fluid restriction: Add oral sodium chloride 100 mEq three times daily 1
• For persistent cases: Consider vasopressin receptor antagonists (tolvaptan 15 mg once daily, titrated to 30-60 mg) or urea 1, 4, 2
• Important: Tolvaptan should be initiated and re-initiated only in a hospital setting with close sodium monitoring 4
• Avoid using tolvaptan for more than 30 days due to hepatotoxicity risk 4

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

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

• Discontinue diuretics temporarily 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 edema and ascites 1
• Vasopressin receptor antagonists may be considered for persistent severe hyponatremia despite fluid restriction and optimization of guideline-directed medical therapy 1

Critical Correction Rate Guidelines

The single most important safety principle is limiting correction rates to prevent osmotic demyelination syndrome:

• Standard patients: Maximum 8 mmol/L per 24 hours 1, 2, 3
• High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy): Maximum 4-6 mmol/L per day 1
• For severe symptoms: Correct 6 mmol/L over first 6 hours, then slow correction to stay within 8 mmol/L total for 24 hours 1

Special Considerations for Neurosurgical Patients

Distinguish between SIADH and cerebral salt wasting (CSW), as treatments are opposite. 1

• CSW requires volume and sodium replacement (isotonic or hypertonic saline), NOT fluid restriction 1
• For severe CSW: Use 3% hypertonic saline plus fludrocortisone 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1
• Consider fludrocortisone or hydrocortisone to prevent natriuresis in these patients 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours, immediate intervention is required:

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse the rapid rise in serum sodium 1
• Goal: Bring total 24-hour correction to no more than 8 mmol/L from starting point 1

Common Pitfalls to Avoid

• Never use fluid restriction as initial treatment for severe symptomatic hyponatremia - this is a medical emergency requiring hypertonic saline 1
• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours - this causes osmotic demyelination syndrome 1, 2
• Never use fluid restriction in cerebral salt wasting - this worsens outcomes 1
• Never use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms - this worsens fluid overload 1
• Never ignore mild hyponatremia (130-135 mmol/L) - even mild hyponatremia increases fall risk and mortality 1, 2
• Inadequate monitoring during active correction leads to overcorrection and osmotic demyelination 1

Monitoring Requirements

• Severe symptoms: Check serum sodium every 2 hours during initial correction 1
• After symptom resolution: Check every 4 hours 1
• Watch for osmotic demyelination syndrome signs (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1