What is the treatment approach for a patient with chronic hyponatremia?

Treatment Approach for Chronic Hyponatremia

For chronic hyponatremia, the treatment strategy depends critically on volume status and symptom severity, with the overriding principle being to never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Classification

• Determine chronicity: Chronic hyponatremia is defined as lasting >48 hours, which fundamentally changes management compared to acute cases 1
• Assess volume status through physical examination looking for orthostatic hypotension, dry mucous membranes (hypovolemic); peripheral edema, ascites, jugular venous distention (hypervolemic); or absence of these findings (euvolemic) 1
• Obtain essential laboratory tests: serum and urine osmolality, urine sodium, urine electrolytes, serum uric acid, thyroid function, and cortisol to determine underlying etiology 1
• Evaluate symptom severity: Even mild chronic hyponatremia (130-135 mmol/L) increases fall risk (21% vs 5% in normonatremic patients) and mortality (60-fold increase with sodium <130 mmol/L) 1, 2

Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Discontinue diuretics immediately if sodium <125 mmol/L 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 with 71-100% positive predictive value 1
• Avoid lactated Ringer's solution as it is hypotonic (130 mEq/L sodium, 273 mOsm/L) and can worsen hyponatremia 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day is the cornerstone of first-line treatment 1, 2
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction alone 1
• Consider urea as an effective second-line option for SIADH resistant to fluid restriction 1, 3
• Tolvaptan 15 mg once daily (titrate to 30-60 mg) may be used for persistent hyponatremia despite fluid restriction, but use with extreme caution due to risk of overly rapid correction 1, 4
• Demeclocycline or lithium are less commonly used alternatives due to side effects 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
• Temporarily discontinue diuretics until sodium improves to >125 mmol/L 1
• Consider albumin infusion in cirrhotic patients alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens ascites and edema 1
• Sodium restriction (not fluid restriction) results in weight loss as fluid passively follows sodium in cirrhotic patients 1

Critical Correction Rate Guidelines

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

• Standard patients: Maximum 8 mmol/L per 24 hours, target 4-8 mmol/L per day 1
• High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy): Maximum 4-6 mmol/L per day, never exceeding 8 mmol/L in 24 hours 1, 5
• Never correct chronic hyponatremia faster than 1 mmol/L/hour 1

Monitoring Protocol

• Asymptomatic or mildly symptomatic patients: Check sodium every 24-48 hours initially 1
• After initiating treatment: Monitor every 4-6 hours until stable 1
• Watch for osmotic demyelination syndrome signs (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 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 rise in serum sodium 1
• Target relowering to bring total 24-hour correction to no more than 8 mmol/L from starting point 1

Special Population Considerations

Cirrhotic Patients

• More cautious correction (4-6 mmol/L per day maximum) due to higher osmotic demyelination risk 1
• Hyponatremia increases complications: spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), hepatic encephalopathy (OR 2.36) 1
• Tolvaptan carries 10% gastrointestinal bleeding risk vs 2% with placebo in cirrhosis 4
• Many cirrhotic patients with chronic hyponatremia at 130-135 mmol/L remain asymptomatic and may not require active treatment beyond managing underlying condition 1

Neurosurgical Patients

• Distinguish SIADH from cerebral salt wasting (CSW) as treatments are opposite 1
• CSW requires volume and sodium replacement, not fluid restriction 1
• For severe CSW symptoms: 3% hypertonic saline plus fludrocortisone 0.1-0.2 mg daily in ICU 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours causes osmotic demyelination syndrome 1
• Using fluid restriction in cerebral salt wasting worsens outcomes 1
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant when it increases fall risk and mortality 1, 2
• Inadequate monitoring during active correction can lead to dangerous overcorrection 1
• Failing to identify and treat underlying cause perpetuates the problem 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms worsens fluid overload 1