What is the treatment for chronic hyponatremia?

Treatment of Chronic Hyponatremia

For chronic hyponatremia, the cornerstone of treatment is addressing the underlying cause combined with volume status-guided therapy: fluid restriction (1-1.5 L/day) for euvolemic/hypervolemic states, isotonic saline for hypovolemic states, and strict adherence to correction rates not exceeding 8 mmol/L per 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Classification

Before initiating treatment, determine three critical factors:

• Volume status: Classify as hypovolemic, euvolemic, or hypervolemic through clinical examination including assessment for edema, orthostatic hypotension, jugular venous distention, and mucous membrane moisture 1
• Chronicity: Chronic hyponatremia is defined as lasting >48 hours, which fundamentally changes correction rate targets 1
• Symptom severity: Even mild chronic hyponatremia (130-135 mmol/L) increases fall risk (21% vs 5% in normonatremic patients) and should not be dismissed as clinically insignificant 1

Essential diagnostic workup includes serum and urine osmolality, urine sodium concentration, urine electrolytes, serum uric acid, and thyroid function tests to identify the underlying etiology 1

Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Discontinue diuretics immediately and administer isotonic saline (0.9% NaCl) for volume repletion 1
• Urinary sodium <30 mmol/L has 71-100% positive predictive value for response to normal saline infusion 1
• Once euvolemia is achieved, reassess sodium levels as correction may occur spontaneously with volume restoration 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day is first-line treatment for mild to moderate asymptomatic cases 1
• If fluid restriction fails after adequate trial, add oral sodium chloride supplementation 100 mEq three times daily 1
• For resistant cases, consider pharmacological options:
  • Tolvaptan (vasopressin V2-receptor antagonist): Start 15 mg once daily, can titrate to 30-60 mg daily based on response 2
  • Urea 15-30 g/day in divided doses (effective but limited by poor palatability) 1, 3
  • Demeclocycline or lithium (less commonly used due to side effect profiles) 1

Critical distinction: In neurosurgical patients, differentiate SIADH from cerebral salt wasting (CSW), as CSW requires volume and sodium replacement rather than fluid restriction—using fluid restriction in CSW worsens outcomes 1

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 drops below 125 mmol/L 1
• For cirrhotic patients specifically:
  • Consider albumin infusion alongside fluid restriction 1
  • Recognize that it is sodium restriction, not fluid restriction, that produces weight loss as fluid passively follows sodium 1
  • Avoid hypertonic saline unless life-threatening symptoms present, as it may worsen ascites and edema 1
• Tolvaptan may be considered for clinically significant hyponatremia resistant to fluid restriction, starting at 15 mg once daily 1, 2
  • Caution: In cirrhotic patients, tolvaptan carries higher risk of gastrointestinal bleeding (10% vs 2% placebo) 1, 2

Correction Rate Guidelines: The Critical Safety Parameter

The maximum correction rate is 8 mmol/L in 24 hours for average-risk patients 1

High-Risk Populations Requiring Slower Correction (4-6 mmol/L per day):

• Advanced liver disease or cirrhosis 1
• Chronic alcoholism 1
• Malnutrition 1
• Prior history of encephalopathy 1
• Severe baseline hyponatremia (<120 mmol/L) 1
• Hypophosphatemia, hypokalemia, or hypoglycemia 1

The risk of osmotic demyelination syndrome in liver transplant recipients is 0.5-1.5%, making cautious correction paramount 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
• Administer desmopressin to slow or reverse the rapid sodium rise 1
• Target relowering to bring total 24-hour correction to ≤8 mmol/L from baseline 1
• Monitor for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1

Monitoring Requirements

• For asymptomatic chronic hyponatremia: Check sodium levels every 4 hours initially during active correction, then daily once stable 1
• During hypertonic saline administration: Monitor every 2 hours 1
• Calculate sodium deficit using: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1

Specific Clinical Scenarios

Moderate Hyponatremia (120-125 mmol/L)

• Fluid restriction to 1000 mL/day for euvolemic/hypervolemic states 1
• For hypervolemic states with cirrhosis, consider more severe fluid restriction plus albumin infusion 1
• Continue diuretics with close electrolyte monitoring if sodium remains >126 mmol/L 1

Mild Hyponatremia (126-135 mmol/L)

• For patients on diuretics with sodium 126-135 mmol/L and normal creatinine: continue diuretic therapy but monitor serum electrolytes closely—water restriction is not recommended at this level 1
• Recognize that even mild hyponatremia is associated with cognitive impairment, gait disturbances, and increased fracture risk 3

Severe Hyponatremia (<120 mmol/L) Without Severe Symptoms

• Stop diuretics immediately 1
• Implement severe fluid restriction with albumin infusion for hypervolemic states 1
• Limit correction to 4-6 mEq/L per day, not exceeding 8 mEq/L in 24 hours 1
• Reserve hypertonic saline for patients with severe symptoms or imminent liver transplantation 1

Common Pitfalls to Avoid

• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant—this increases mortality and fall risk 1
• Using fluid restriction in cerebral salt wasting—this worsens outcomes 1
• Overly rapid correction exceeding 8 mmol/L in 24 hours, leading to osmotic demyelination syndrome 1
• Inadequate monitoring during active correction 1
• Failing to identify and treat the underlying cause 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Administering normal saline to euvolemic patients with SIADH—this may worsen hyponatremia 1

Special Population Considerations

Neurosurgical Patients

• Cerebral salt wasting is more common than SIADH in this population 1
• For CSW: treat with volume and sodium replacement, consider fludrocortisone or hydrocortisone 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk for vasospasm 1

Cirrhotic Patients

• Hyponatremia reflects worsening hemodynamic status 1
• Serum sodium ≤130 mEq/L increases risk for hepatic encephalopathy (OR 2.36), hepatorenal syndrome (OR 3.45), and spontaneous bacterial peritonitis (OR 3.40) 1
• Sodium levels of 130-135 mmol/L are often tolerated without specific treatment in stable chronic cases 1