What is the treatment approach for an adult patient with moderate to severe hyponatremia, potentially with underlying heart failure or liver disease?

Treatment of Hyponatremia

The treatment of hyponatremia must be guided by three critical factors: symptom severity, volume status (hypovolemic, euvolemic, or hypervolemic), and correction rate limits to prevent osmotic demyelination syndrome. 1

Initial Assessment

Before initiating treatment, rapidly determine:

• Symptom severity: Severe symptoms (seizures, coma, altered mental status) require immediate hypertonic saline; mild symptoms (nausea, weakness, headache) allow for more conservative management 1, 2
• Volume status: Assess for signs of hypovolemia (orthostatic hypotension, dry mucous membranes, decreased skin turgor), euvolemia, or hypervolemia (edema, ascites, jugular venous distention) 1
• Serum sodium level: Mild (130-134 mEq/L), moderate (125-129 mEq/L), or severe (<125 mEq/L) 3
• Chronicity: Acute (<48 hours) versus chronic (>48 hours) - this determines safe correction rates 1

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

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

• Administer 3% hypertonic saline as 100 mL boluses over 10 minutes, repeatable up to three times at 10-minute intervals 1
• Target: increase sodium by 4-6 mEq/L within 1-2 hours to reverse hyponatremic encephalopathy 2
• Critical safety limit: Never exceed 8 mEq/L correction in 24 hours to prevent osmotic demyelination syndrome 1, 2
• 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). Correction should be gradual at 4-6 mEq/L per day, not exceeding 8 mEq/L in 24 hours 1

Treatment Based on Volume Status

Hypovolemic Hyponatremia

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

• Initial infusion rate: 15-20 mL/kg/h, then 4-14 mL/kg/h based on response 1
• Urine sodium <30 mmol/L predicts good response to saline (positive predictive value 71-100%) 1
• Once euvolemic, reassess and adjust management based on underlying cause 1

Euvolemic Hyponatremia (SIADH)

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

• First-line: Fluid restriction to <1 L/day 1, 3
• 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, 4
• Alternative pharmacological options: Urea, demeclocycline, or lithium (less commonly used due to side effects) 1, 2

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mEq/L and treat the underlying condition. 1

• Fluid restriction to 1000-1500 mL/day 1
• Temporarily discontinue diuretics if sodium <125 mEq/L 1
• For cirrhosis: Consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1
• For persistent severe hyponatremia despite fluid restriction: Consider tolvaptan with caution (higher risk of GI bleeding in cirrhosis: 10% vs 2% placebo) 1, 4

Special Populations Requiring Cautious Correction

Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy require even slower correction at 4-6 mEq/L per day (maximum 8 mEq/L in 24 hours) due to higher risk of osmotic demyelination syndrome. 1

Neurosurgical Patients: Distinguishing SIADH from Cerebral Salt Wasting (CSW)

This distinction is critical as treatments are opposite:

• SIADH: Euvolemic, treat with fluid restriction 1
• CSW: Hypovolemic (CVP <6 cm H₂O), treat with volume and sodium replacement with isotonic or hypertonic saline, plus fludrocortisone 0.1-0.2 mg daily for severe symptoms 1
• Never use fluid restriction in CSW or subarachnoid hemorrhage patients at risk of vasospasm - this worsens outcomes 1

Monitoring and Prevention of Overcorrection

• Severe symptoms: Check sodium every 2 hours during initial correction 1
• Mild symptoms: Check sodium every 4 hours initially, then daily 1
• If overcorrection occurs (>8 mEq/L in 24 hours): Immediately discontinue current fluids, switch to D5W (5% dextrose in water), and consider desmopressin to slow or reverse the rapid rise 1, 5
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1

Common Pitfalls to Avoid

• Never correct chronic hyponatremia faster than 8 mEq/L in 24 hours - this causes osmotic demyelination syndrome 1, 2
• Inadequate monitoring during active correction 1
• Using fluid restriction in cerebral salt wasting - this worsens outcomes 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Failing to recognize and treat the underlying cause 1
• Ignoring mild hyponatremia (130-135 mEq/L) as clinically insignificant - even mild hyponatremia increases fall risk (21% vs 5%) and mortality (60-fold increase with sodium <130 mEq/L) 1, 2