What is the recommended management for a patient with serum sodium of 128 mmol/L?

Management of Serum Sodium 128 mmol/L

For a patient with serum sodium of 128 mmol/L, continue current diuretic therapy with close monitoring of serum electrolytes, and do not implement water restriction at this level. 1

Initial Assessment

• Determine volume status through clinical examination looking for orthostatic hypotension, dry mucous membranes, decreased skin turgor (hypovolemic); peripheral edema, ascites, jugular venous distention (hypervolemic); or absence of these findings (euvolemic) 2
• Obtain urine sodium and osmolality to differentiate underlying causes: urine sodium <30 mmol/L suggests hypovolemic hyponatremia responsive to saline, while >20-40 mmol/L with high urine osmolality suggests SIADH 2
• Check serum osmolality to exclude pseudohyponatremia from hyperglycemia (add 1.6 mEq/L to sodium for each 100 mg/dL glucose >100 mg/dL) 2
• Review medications particularly diuretics, SSRIs, carbamazepine, NSAIDs, and opioids as common culprits 2

Management Based on Volume Status

Hypovolemic Hyponatremia (True Volume Depletion)

• Administer isotonic saline (0.9% NaCl) at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on response 2
• Discontinue diuretics immediately 2
• Target correction rate: 4-8 mmol/L per day, never exceeding 8 mmol/L in 24 hours 2

Euvolemic Hyponatremia (SIADH)

• Implement fluid restriction to 1 L/day as first-line therapy 2
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction 2
• Consider vaptans (tolvaptan 15 mg once daily) for resistant cases, though use cautiously due to risk of overly rapid correction 3, 4
• Avoid fluid restriction during first 24 hours if starting tolvaptan to prevent overcorrection 3

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Continue diuretics at sodium 126-135 mmol/L with normal creatinine 1
• Monitor serum electrolytes closely but do not restrict water at this level 1
• Implement fluid restriction to 1-1.5 L/day only if sodium drops below 125 mmol/L 2
• Consider albumin infusion in cirrhotic patients alongside fluid restriction 2

Critical Safety Considerations

• Maximum correction rate: Never exceed 8 mmol/L in any 24-hour period to prevent osmotic demyelination syndrome 2, 5
• High-risk patients (advanced liver disease, alcoholism, malnutrition) require even slower correction at 4-6 mmol/L per day 2
• Monitor sodium levels every 24-48 hours initially to ensure safe correction 2

Common Pitfalls to Avoid

• Do not implement water restriction at sodium 128 mmol/L—this is unnecessary and potentially harmful at this mild level 1
• Do not stop diuretics prematurely in volume-overloaded patients, as persistent fluid overload worsens outcomes 2
• Do not use hypotonic fluids (lactated Ringer's, 0.45% saline) as these can worsen hyponatremia 2
• Do not correct too rapidly—even mild chronic hyponatremia corrected faster than 8 mmol/L in 24 hours risks osmotic demyelination 2, 5

Special Populations

• Cirrhotic patients: Hyponatremia at this level increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 2
• Neurosurgical patients: Distinguish between SIADH (requires fluid restriction) and cerebral salt wasting (requires volume replacement, never fluid restriction) 2
• Heart failure patients: Continue guideline-directed medical therapy including diuretics; fluid restriction benefit is uncertain at this sodium level 2

When to Escalate Treatment

• Sodium drops below 125 mmol/L: Stop diuretics, implement fluid restriction (hypervolemic) or give volume expansion (hypovolemic) 1
• Severe symptoms develop (seizures, coma, altered mental status): Administer 3% hypertonic saline targeting 6 mmol/L correction over 6 hours 2, 5
• Sodium <120 mmol/L: Requires immediate intervention regardless of symptoms 1