What is the treatment approach for hyponatremia?

Treatment of Hyponatremia

The treatment of hyponatremia must be guided by symptom severity, volume status, and correction rate limits—with severe symptomatic cases requiring immediate 3% hypertonic saline to correct 6 mmol/L over 6 hours, while chronic cases demand cautious correction not exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment

Diagnostic Workup

• Obtain serum and urine osmolality, urine sodium, uric acid, and assess extracellular fluid volume status when serum sodium <135 mmol/L 1
• Classify by volume status: hypovolemic (orthostatic hypotension, dry mucous membranes, decreased skin turgor), euvolemic (no edema, normal blood pressure), or hypervolemic (peripheral edema, ascites, jugular venous distention) 1, 2
• Urine sodium <30 mmol/L suggests hypovolemic hyponatremia with 71-100% positive predictive value for saline response 1
• Serum uric acid <4 mg/dL has 73-100% positive predictive value for SIADH 1

Determine Acuity and Symptom Severity

• Acute (<48 hours)** vs. **chronic (>48 hours) onset determines correction rate safety 1
• Severe symptoms (seizures, coma, altered consciousness, confusion) constitute a medical emergency 1, 3, 4
• Moderate symptoms include nausea, vomiting, headache, weakness 3, 5
• Mild/asymptomatic cases still require attention as even sodium 130-135 mmol/L increases fall risk 60-fold and mortality 1, 3

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

• Administer 3% hypertonic saline immediately with goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1, 4, 5
• Give as 100 mL boluses over 10 minutes, repeatable up to three times at 10-minute intervals 1
• Maximum correction: 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2, 4
• Monitor serum sodium every 2 hours during initial correction 1
• Consider ICU admission for close monitoring 1

Mild to Moderate Symptomatic or Asymptomatic Hyponatremia

Treatment depends on volume status (see below) 1, 5

Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Discontinue diuretics immediately 1
• 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 1
• Urine sodium <30 mmol/L predicts good response to saline 1
• Once euvolemic, reassess and adjust management 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day is the cornerstone of treatment 1, 4, 6
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• For severe symptoms: use 3% hypertonic saline as above 1
• Pharmacological options for resistant cases:
  • Tolvaptan 15 mg once daily (vasopressin receptor antagonist), titrate to 30-60 mg 1, 7, 8
  • Urea 40 g in 100-150 mL normal saline every 8 hours 1
  • Demeclocycline or lithium (less commonly used due to side effects) 1, 6

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1, 5, 6
• 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 present, as it worsens edema and ascites 1
• Tolvaptan may be considered for persistent severe hyponatremia despite fluid restriction, but use with extreme caution in cirrhosis due to 10% gastrointestinal bleeding risk vs. 2% with placebo 1, 7

Critical Correction Rate Guidelines

Standard Patients

• Maximum 8 mmol/L in 24 hours 1, 2, 4
• Target 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)

• Maximum 4-6 mmol/L per day, not exceeding 8 mmol/L in 24 hours 1, 9, 4
• These patients have significantly higher risk of osmotic demyelination syndrome 1, 9

Monitoring During Correction

• Severe symptoms: check sodium every 2 hours 1
• After symptom resolution: check every 4 hours 1
• Continue monitoring for 2-7 days post-correction for signs of osmotic demyelination (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) 1, 9

Special Considerations: Neurosurgical Patients

Cerebral Salt Wasting (CSW) vs. SIADH

• CSW requires volume and sodium replacement, NOT fluid restriction 1, 4
• CSW features: true hypovolemia, CVP <6 cm H₂O, high urine sodium >20 mmol/L despite volume depletion 1
• Treatment for CSW:
  • Isotonic or hypertonic saline for volume replacement 1
  • For severe symptoms: 3% hypertonic saline plus fludrocortisone in ICU 1
  • Hydrocortisone may prevent natriuresis in subarachnoid hemorrhage patients 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 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, 9
• Consider administering desmopressin to slow or reverse rapid rise 1, 9
• Goal: bring total 24-hour correction to no more than 8 mmol/L from starting point 1

Common Pitfalls to Avoid

• Overly rapid correction (>8 mmol/L in 24 hours) causing osmotic demyelination syndrome 1, 9, 4
• Using fluid restriction in cerebral salt wasting, which worsens outcomes 1, 9
• Inadequate monitoring during active correction 1, 9
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant—it increases mortality and fall risk 1, 3
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1, 9
• Failing to identify and treat underlying cause 1, 9