What is the approach for correcting hyponatremia?

Hyponatremia Correction

Correct hyponatremia based on symptom severity and chronicity, with a maximum correction rate of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome, using 3% hypertonic saline for severe symptoms and fluid restriction for chronic asymptomatic cases. 1

Initial Assessment

Before initiating correction, determine three critical factors:

• Symptom severity: Severe symptoms (seizures, coma, altered mental status) versus mild symptoms (nausea, headache) versus asymptomatic 1
• Chronicity: Acute (<48 hours) versus chronic (>48 hours) onset 1
• Volume status: Hypovolemic (dehydration, orthostatic hypotension, dry mucous membranes), euvolemic (normal volume status), or hypervolemic (edema, ascites, jugular venous distention) 1

Obtain serum and urine osmolality, urine sodium, and urine electrolytes to determine the underlying cause 1. A urine sodium <30 mmol/L suggests hypovolemic hyponatremia responsive to saline, while >20 mmol/L with high urine osmolality suggests SIADH 1.

Treatment Algorithm Based on Symptom Severity

Severe Symptomatic Hyponatremia (Seizures, Coma, Altered Mental Status)

This is a medical emergency requiring immediate intervention with hypertonic saline, not fluid restriction. 1

• Administer 3% hypertonic saline immediately with a target correction of 6 mmol/L over the first 6 hours or until severe symptoms resolve 1
• Monitor serum sodium every 2 hours during initial correction 1
• Do not exceed 8 mmol/L total correction in 24 hours to prevent osmotic demyelination syndrome 1, 2
• After achieving 6 mmol/L correction in 6 hours, limit additional correction to only 2 mmol/L in the remaining 18 hours 1
• Discontinue 3% saline when severe symptoms resolve, then transition to protocols for mild symptoms or asymptomatic hyponatremia 3

The FDA label for tolvaptan warns that correction >12 mEq/L/24 hours can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, affective changes, spastic quadriparesis, seizures, coma and death 2.

Mild Symptomatic or Asymptomatic Hyponatremia

Treatment depends on volume status:

For Hypovolemic Hyponatremia:

• Discontinue diuretics immediately 1
• Administer isotonic saline (0.9% NaCl) for volume repletion 1
• Correct at a rate not exceeding 8 mmol/L in 24 hours 1

For Euvolemic Hyponatremia (SIADH):

• Fluid restriction to 1 L/day is the cornerstone of treatment 1
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• For severe cases, consider 3% hypertonic saline with careful monitoring 1
• Vasopressin receptor antagonists (tolvaptan 15 mg once daily) may be considered for resistant cases 1, 2

For 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 <125 mmol/L 1
• Consider albumin infusion in cirrhotic patients 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1

Critical Correction Rate Guidelines

Standard correction limits:

• Maximum 8 mmol/L in 24 hours for most patients 1, 2
• For severe symptoms: 6 mmol/L over 6 hours, then limit to 2 mmol/L in remaining 18 hours 1

High-risk patients require slower correction (4-6 mmol/L per day):

• Advanced liver disease 1
• Alcoholism 1
• Malnutrition 1
• Prior encephalopathy 1

The FDA label specifically warns that in susceptible patients, including those with severe malnutrition, alcoholism or advanced liver disease, slower rates of correction may be advisable 2.

Special Considerations for Neurosurgical Patients

Distinguish between SIADH and Cerebral Salt Wasting (CSW), as treatment approaches differ fundamentally 1:

For CSW:

• Treatment focuses on volume and sodium replacement, NOT fluid restriction 1
• Use isotonic or hypertonic saline based on severity 1
• For severe symptoms, administer 3% hypertonic saline plus fludrocortisone in ICU 1
• Using fluid restriction in CSW worsens outcomes 1

For subarachnoid hemorrhage patients at risk of vasospasm:

• Do NOT use fluid restriction 1
• Consider fludrocortisone to prevent vasospasm 1
• Hydrocortisone may prevent natriuresis 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours 1:

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse the rapid rise in serum sodium 1
• Target reduction to bring total 24-hour correction to no more than 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

Common Pitfalls to Avoid

• Never ignore mild hyponatremia (130-135 mmol/L) as clinically insignificant—it increases fall risk (21% vs 5%) and mortality (60-fold increase) 1, 4
• Never use fluid restriction as initial treatment for severe symptomatic hyponatremia—this is a medical emergency requiring hypertonic saline 1
• Never exceed 8 mmol/L correction in 24 hours—overcorrection risks osmotic demyelination syndrome 1, 2
• Never use fluid restriction in cerebral salt wasting—it worsens outcomes 1
• Never use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms—it worsens fluid overload 1
• Inadequate monitoring during active correction leads to complications 1
• Failing to recognize and treat the underlying cause results in poor outcomes 1

Monitoring Requirements

During active correction:

• Severe symptoms: Check serum sodium every 2 hours 1
• After symptom resolution: Check every 4 hours 1
• Asymptomatic patients: Check every 24 hours initially 1

Watch for osmotic demyelination syndrome signs (typically 2-7 days post-correction): dysarthria, dysphagia, oculomotor dysfunction, quadriparesis 1