How to correct hyponatremia (low serum sodium levels)?

Management of Hyponatremia

The treatment of hyponatremia should be based on symptom severity, volume status, and rate of onset, with correction rates not exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Classification

• Hyponatremia is defined as serum sodium <135 mmol/L, with severity classified as mild (126-135 mEq/L), moderate (120-125 mEq/L), and severe (<120 mEq/L) 1
• Determine volume status (hypovolemic, euvolemic, or hypervolemic) through clinical assessment of extracellular fluid volume 1
• Check urine sodium and osmolality to differentiate between SIADH and other causes 1
• Assess symptom severity: mild (nausea, headache), moderate (confusion), or severe (seizures, coma) 1

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Seizures, Coma)

• Administer 3% hypertonic saline immediately with an initial goal to increase sodium by 4-6 mmol/L over 6 hours or until severe symptoms resolve 1, 2
• Use boluses of 100 mL over 10 minutes, which can be repeated up to three times at 10-minute intervals until symptoms improve 1
• Total correction should not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2
• Discontinue 3% saline when severe symptoms resolve and transition to protocols for mild symptoms or asymptomatic hyponatremia 2

Mild to Moderate Symptomatic Hyponatremia

• For euvolemic hyponatremia (SIADH): fluid restriction to 1 L/day is the cornerstone of treatment 1, 3
• If no response to fluid restriction, add sodium chloride 100 mEq orally three times daily 3
• For hypovolemic hyponatremia: discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 1
• For hypervolemic hyponatremia (cirrhosis, heart failure): fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1

Correction Rate Guidelines

• Maximum increase of 8 mmol/L in 24 hours for most patients 1, 2, 3
• For patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy: more cautious correction (4-6 mmol/L per day) 1
• Calculate sodium deficit using formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1
• Monitor serum sodium every 2-4 hours during initial correction for severe symptoms 1

Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Discontinue diuretics that may be contributing to hyponatremia 1
• Administer isotonic saline (0.9% NaCl) to restore intravascular volume 1
• For severe dehydration with neurological symptoms, consider hypertonic saline with careful monitoring 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day is first-line treatment 1, 3
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction 3
• Consider pharmacological options for resistant cases: vasopressin receptor antagonists (tolvaptan), urea, demeclocycline, or lithium 1, 4
• Tolvaptan should be initiated only in a hospital setting where serum sodium can be monitored closely 4

Hypervolemic Hyponatremia (Cirrhosis, Heart Failure)

• Fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L 1
• Consider albumin infusion for patients with cirrhosis 1
• Avoid hypertonic saline unless life-threatening symptoms are present 1
• Temporarily discontinue diuretics if sodium <125 mmol/L 1

Special Considerations

Cerebral Salt Wasting vs. SIADH

• In neurosurgical patients, distinguish between SIADH and cerebral salt wasting (CSW) as treatment approaches differ significantly 1
• CSW requires volume and sodium replacement, not fluid restriction 1
• Consider fludrocortisone for hyponatremia in subarachnoid hemorrhage patients 1
• Avoid fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1

Pharmacological Interventions

• Tolvaptan (vasopressin receptor antagonist) is effective for euvolemic or hypervolemic hyponatremia 4
• Initiate tolvaptan only in a hospital setting at 15 mg once daily, with possible increase to 30 mg and then 60 mg at 24-hour intervals 4
• Too rapid correction with tolvaptan (>12 mEq/L/24 hours) can cause osmotic demyelination 4
• Avoid tolvaptan in patients with ADPKD due to risk of hepatotoxicity 4

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours, which can lead to osmotic demyelination syndrome 1, 5
• Inadequate monitoring during active correction 1
• Using fluid restriction in cerebral salt wasting, which can worsen outcomes 1
• Failing to recognize and treat the underlying cause 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant, as even mild hyponatremia is associated with neurocognitive problems, falls, and increased mortality 5, 6

Management of Overcorrection

• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1, 7
• Desmopressin can be administered parenterally (1-2 μg every 6-8 hours) alongside careful hypertonic saline administration to achieve controlled correction 7
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1