How do I correct a serum sodium of 128 mmol/L?

Correcting Serum Sodium of 128 mmol/L

For a serum sodium of 128 mmol/L, the approach depends entirely on symptom severity and volume status: if the patient has severe symptoms (altered mental status, seizures, coma), immediately administer 3% hypertonic saline targeting a 6 mmol/L rise over 6 hours; if asymptomatic or mildly symptomatic, determine whether the patient is hypovolemic (give isotonic saline), euvolemic (fluid restriction ± oral sodium), or hypervolemic (fluid restriction to 1-1.5 L/day), while never exceeding 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment

Before initiating treatment, rapidly determine three critical factors that guide management:

• Symptom severity: Severe symptoms (confusion, seizures, coma, respiratory distress) constitute a medical emergency requiring immediate hypertonic saline, regardless of the absolute sodium value 1, 2. Mild symptoms include nausea, headache, weakness, and gait instability 2, 3.

• Volume status: Assess for hypovolemia (orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins), euvolemia (normal examination), or hypervolemia (peripheral edema, ascites, jugular venous distention) 1. Physical examination alone has limited accuracy (sensitivity 41%, specificity 80%), so incorporate urine sodium and osmolality 1.

• Acuity: Acute hyponatremia (<48 hours) causes more severe symptoms than chronic hyponatremia at the same sodium level and can be corrected more rapidly 1, 2, 4. If large volumes of hypotonic fluid were administered within 2-3 days, assume acute hyponatremia 4.

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

Administer 3% hypertonic saline immediately with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve 1, 5, 6:

• Give 100 mL boluses of 3% NaCl IV over 10 minutes, repeating up to three times at 10-minute intervals 1
• Check serum sodium every 2 hours during initial correction 1, 5
• Once symptoms resolve or 6 mmol/L is achieved, switch to maintenance therapy based on volume status 1
• Critical safety limit: Total correction must not exceed 8 mmol/L in any 24-hour period 1, 5, 6

Asymptomatic or Mildly Symptomatic Hyponatremia

Treatment is determined by volume status:

Hypovolemic Hyponatremia

• 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
• Discontinue any diuretics immediately 1
• Urine sodium <30 mmol/L predicts good response to saline (positive predictive value 71-100%) 1
• For cirrhotic patients, consider albumin infusion (8 g per liter of ascites removed) alongside saline 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day is first-line therapy 1, 7
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• For resistant cases, consider pharmacologic options: urea, demeclocycline, lithium, or vaptans (tolvaptan 15 mg once daily, titrate to 30-60 mg) 1, 7, 6

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
• Temporarily discontinue diuretics if sodium <125 mmol/L 1
• For cirrhotic patients, consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it worsens ascites and edema 1
• Treat the underlying condition (optimize heart failure therapy, manage cirrhosis) 1

Critical Correction Rate Guidelines

The single most important safety principle is never exceeding 8 mmol/L correction in 24 hours 1, 5, 6:

• Standard-risk patients: Target 4-8 mmol/L per day, maximum 10-12 mmol/L in 24 hours 1
• High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy): Limit to 4-6 mmol/L per day, absolute maximum 8 mmol/L in 24 hours 1, 5
• The maximum change in osmolality should not exceed 3 mOsm/kg H₂O per hour 5

Monitoring Protocol

• Severe symptoms: Check sodium every 2 hours during initial correction 1, 5
• Mild symptoms or asymptomatic: Check sodium every 4 hours initially, then daily 1, 5
• Monitor for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically appearing 2-7 days after rapid correction 1, 5

Management of Overcorrection

If sodium rises >8 mmol/L in 24 hours:

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water) 1, 5
• Consider administering desmopressin to slow or reverse the rapid rise 1, 5
• Target is to bring total 24-hour correction back to ≤8 mmol/L from baseline 1

Special Populations

Neurosurgical Patients

• Distinguish between SIADH (euvolemic, treat with fluid restriction) and cerebral salt wasting (hypovolemic, treat with volume and sodium replacement) 1
• Never use fluid restriction in cerebral salt wasting or subarachnoid hemorrhage patients at risk of vasospasm, as this worsens outcomes 1
• Consider fludrocortisone 0.1-0.2 mg daily for severe cerebral salt wasting 1

Cirrhotic Patients

• Hyponatremia in cirrhosis increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
• Require especially cautious correction (4-6 mmol/L per day) due to higher risk of osmotic demyelination 1
• Sodium restriction (not fluid restriction) results in weight loss, as fluid follows sodium 1

Common Pitfalls to Avoid

• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours—this causes osmotic demyelination syndrome 1, 5
• Never use fluid restriction as initial treatment for altered mental status—this is a medical emergency requiring hypertonic saline 1
• Never ignore mild hyponatremia (130-135 mmol/L) as clinically insignificant—it increases mortality 60-fold and fall risk from 5% to 21% 1, 2
• Never use hypotonic fluids (0.45% saline, lactated Ringer's, D5W) in hyponatremia, as they worsen the condition 1
• Never apply the same treatment to all hyponatremia—volume status determines therapy 1, 3