What is the recommended approach for correcting sodium levels in patients with severe, symptomatic hyponatremia?

Management of Severe Symptomatic Hyponatremia

For severe symptomatic hyponatremia, administer 3% hypertonic saline with an initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve, then limit correction to a maximum of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Classification

• Hyponatremia is defined as serum sodium <135 mmol/L and should be classified by severity, volume status, and symptom severity 1
• Initial workup should include serum and urine osmolarity, urine electrolytes, uric acid, and assessment of extracellular fluid volume status to determine the underlying cause 1
• Determine acuity of onset: acute (<48 hours) versus chronic (>48 hours), as this affects the correction strategy 1

Treatment Based on Symptom Severity

For Severe Symptoms (seizures, coma, severe neurological deficits)

• Administer 3% hypertonic saline with an initial goal to correct 6 mmol/L over 6 hours or until severe symptoms resolve 1, 2
• After severe symptoms resolve, switch to protocols for mild symptoms or asymptomatic hyponatremia 2
• Continue monitoring serum sodium levels every 2 hours during initial correction, then every 4 hours after resolution of severe symptoms 1, 2
• Consider ICU admission for close monitoring during treatment 1

For Mild Symptoms or Asymptomatic Patients

• Implement fluid restriction to 1 L/day, especially for SIADH 1, 2
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• For hypovolemic hyponatremia, discontinue diuretics and administer isotonic saline (0.9% NaCl) for volume repletion 1

Correction Rate Guidelines

• Do not exceed total correction of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2
• After initial 6 mmol/L correction, limit to only 2 mmol/L in the following 18 hours 2
• For patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy, use more cautious correction rates (4-6 mmol/L per day) due to higher risk of osmotic demyelination 1
• If overcorrection occurs, consider relowering with electrolyte-free water or desmopressin 1

Treatment Based on Volume Status

For Euvolemic Hyponatremia (SIADH)

• Primary treatment is fluid restriction to 1 L/day 1
• Consider additional options: urea, diuretics, lithium, demeclocycline 1
• For resistant cases, vasopressin receptor antagonists like tolvaptan may be considered, but must be initiated in a hospital setting 3

For Hypervolemic Hyponatremia (cirrhosis, heart failure)

• Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L 1
• Consider albumin infusion for patients with cirrhosis 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1

For Cerebral Salt Wasting (in neurosurgical patients)

• Treatment focuses on volume and sodium replacement, not fluid restriction 1
• For severe symptoms, administer 3% hypertonic saline and consider fludrocortisone 1
• Avoid fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1

Special Considerations

• Tolvaptan should be initiated and re-initiated only in a hospital where serum sodium can be monitored closely 3
• Too rapid correction of hyponatremia (>12 mEq/L/24 hours) can cause osmotic demyelination resulting in dysarthria, mutism, dysphagia, lethargy, affective changes, spastic quadriparesis, seizures, coma, and death 3
• In patients with hyperglycemia, calculate corrected serum sodium by adding 1.6 mEq/L to the measured sodium value for every 100 mg/dL of glucose above 100 mg/dL 4
• 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

• Overly rapid correction of chronic hyponatremia leading to osmotic demyelination syndrome 1, 3
• Inadequate monitoring during active correction 1
• Using fluid restriction in cerebral salt wasting, which can worsen outcomes 1
• Failing to recognize and treat the underlying cause 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1