How to correct hyponatremia in a patient?

How to Correct Hyponatremia

The correction of hyponatremia depends critically on three factors: symptom severity (severe vs. mild/asymptomatic), volume status (hypovolemic, euvolemic, or hypervolemic), and chronicity (acute <48 hours vs. chronic >48 hours), with the overriding principle being that correction must never exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment

Before initiating treatment, rapidly determine:

• Symptom severity: Severe symptoms include seizures, coma, altered mental status, or cardiorespiratory distress; mild symptoms include nausea, headache, confusion 1, 2
• Volume status: Assess for orthostatic hypotension, dry mucous membranes (hypovolemic); peripheral edema, ascites, jugular venous distention (hypervolemic); or absence of these findings (euvolemic) 1
• Serum and urine studies: Obtain serum osmolality, urine osmolality, and urine sodium concentration to guide diagnosis 1
• Chronicity: Acute hyponatremia (<48 hours) can be corrected more rapidly; chronic (>48 hours or unknown duration) requires slower correction 1, 3

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 mmol/L over the first 6 hours or until symptoms resolve. 1, 4

• 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 mmol/L in first 1-2 hours to reverse cerebral edema 1, 4
• Monitor serum sodium every 2 hours during initial correction phase 1
• Total correction limit: Maximum 8 mmol/L in 24 hours (if 6 mmol/L corrected in first 6 hours, only 2 mmol/L additional allowed in next 18 hours) 1, 4
• Discontinue 3% saline once severe symptoms resolve and transition to protocols for mild symptoms 5

Mild Symptomatic or Asymptomatic Hyponatremia

Treatment is determined by volume status:

Treatment Based on Volume Status

Hypovolemic Hyponatremia

For patients with true volume depletion (orthostatic hypotension, dry mucous membranes, urine sodium <30 mmol/L), administer isotonic saline (0.9% NaCl) for volume repletion. 1, 6

• Discontinue diuretics immediately if sodium <125 mmol/L 1
• Infusion rate: Initial 15-20 mL/kg/hour, then 4-14 mL/kg/hour based on response 1
• Monitor sodium every 4-6 hours to ensure correction does not exceed 8 mmol/L/24 hours 1
• Urine sodium <30 mmol/L predicts good response to saline with 71-100% positive predictive value 1

Euvolemic Hyponatremia (SIADH)

For SIADH, fluid restriction to 1 L/day is the cornerstone of treatment for mild to moderate cases. 1, 7

• Fluid restriction: Limit to 1000 mL/day as first-line therapy 1
• If no response to fluid restriction: Add oral sodium chloride 100 mEq (approximately 6 grams) three times daily 1
• For persistent hyponatremia: Consider vasopressin receptor antagonists (tolvaptan 15 mg once daily, titrate to 30-60 mg) 8
• Avoid fluid restriction during first 24 hours if using tolvaptan to prevent overly rapid correction 8
• Monitor sodium every 24 hours initially, then adjust frequency based on response 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

For patients with fluid overload (edema, ascites), implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L. 1, 6

• Fluid restriction: 1000-1500 mL/day for sodium <125 mmol/L 1
• 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
• Sodium restriction (not just fluid restriction) is key—fluid follows sodium passively 1

Critical Correction Rate Guidelines

The single most important safety principle is never exceeding 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome. 1, 4

Standard Correction Rates

• Average-risk patients: 4-8 mmol/L per day, maximum 10-12 mmol/L in 24 hours 1
• High-risk patients (advanced liver disease, alcoholism, malnutrition, severe hyponatremia): 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours 1, 8
• Acute hyponatremia (<48 hours): Can correct at 1 mmol/L/hour until symptoms resolve, but still respect 24-hour limit 1, 3
• Chronic hyponatremia (>48 hours): Slower correction mandatory—0.5 mmol/L/hour maximum 1, 9

Monitoring Frequency

• Severe symptoms: Check sodium every 2 hours during active correction 1
• Mild symptoms: Check sodium every 4 hours initially 1
• After symptom resolution: Check sodium every 24 hours 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours, immediately intervene to prevent osmotic demyelination syndrome. 1

• Discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Administer desmopressin to slow or reverse rapid sodium rise 1
• Target: Bring total 24-hour correction back to ≤8 mmol/L from starting point 1
• Watch for osmotic demyelination signs (dysarthria, dysphagia, quadriparesis) typically 2-7 days post-correction 1, 8

Special Populations and Considerations

Neurosurgical Patients

In neurosurgical patients, distinguish between SIADH and cerebral salt wasting (CSW), as they require opposite treatments. 1

• SIADH: Euvolemic, treat with fluid restriction 1
• CSW: Hypovolemic (CVP <6 cm H₂O), treat with volume and sodium replacement, NOT fluid restriction 1
• For CSW with severe symptoms: Use 3% hypertonic saline plus fludrocortisone 0.1-0.2 mg daily 1
• Subarachnoid hemorrhage patients: Never use fluid restriction if at risk for vasospasm 1

Cirrhotic Patients

Patients with cirrhosis require more cautious correction (4-6 mmol/L per day maximum) due to higher risk of osmotic demyelination. 1

• Hyponatremia in cirrhosis increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
• Avoid hypertonic saline unless life-threatening symptoms, as it worsens ascites 1
• Albumin infusion may be beneficial alongside fluid restriction 1

Patients on Diuretics

• For sodium 126-135 mmol/L: Continue diuretics with close electrolyte monitoring 1
• For sodium 121-125 mmol/L: Consider more cautious approach 1
• For sodium ≤120 mmol/L: Stop diuretics immediately and consider volume expansion 1

Pharmacological Options

Vasopressin Receptor Antagonists (Vaptans)

Tolvaptan is FDA-approved for euvolemic and hypervolemic hyponatremia but must be initiated in hospital with close sodium monitoring. 8

• Starting dose: 15 mg once daily, titrate to 30-60 mg based on response 8
• Avoid fluid restriction first 24 hours to prevent overly rapid correction 8
• Maximum duration: 30 days to minimize liver injury risk 8
• Contraindications: Hypovolemic hyponatremia, inability to sense thirst, strong CYP3A inhibitors, anuria 8
• Caution in cirrhosis: Higher risk of GI bleeding (10% vs 2% placebo) 1

Alternative Agents for SIADH

• Urea: 40 grams in 100-150 mL normal saline every 8 hours (effective but poor palatability) 1, 4
• Demeclocycline: May be considered for resistant SIADH 1
• Loop diuretics: Can be used in combination with hypertonic saline for chronic hyponatremia 1, 3

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours causes osmotic demyelination syndrome 1, 4
• Using fluid restriction in cerebral salt wasting worsens outcomes 1
• Inadequate monitoring during active correction 1
• Failing to distinguish acute from chronic hyponatremia leads to inappropriate correction rates 3
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms worsens edema 1
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant—it increases fall risk and mortality 1, 2
• Using lactated Ringer's solution for hyponatremia treatment—it is hypotonic (130 mEq/L sodium) and can worsen hyponatremia 1