How to manage severe hyponatremia of 115 mmol/L?

Management of Severe Hyponatremia (Sodium 115 mmol/L)

For severe hyponatremia at 115 mmol/L, immediately assess symptom severity: if the patient has severe symptoms (seizures, altered mental status, coma), administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours; if asymptomatic or mildly symptomatic, determine volume status and treat the underlying cause while limiting correction to 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Immediate Assessment Required

Determine symptom severity first - this dictates urgency of treatment 1:

• Severe symptoms (seizures, coma, altered mental status, cardiorespiratory distress): Medical emergency requiring immediate hypertonic saline 1, 2
• Mild symptoms (nausea, vomiting, headache, weakness): Less urgent, allows time for diagnostic workup 1, 3
• Asymptomatic: Focus on underlying cause and slower correction 1

Assess volume status through physical examination 1:

• Hypovolemic: Orthostatic hypotension, dry mucous membranes, decreased skin turgor, tachycardia 1
• Euvolemic: No edema, normal blood pressure, moist mucous membranes 1
• Hypervolemic: Peripheral edema, ascites, jugular venous distention 1

Treatment Algorithm Based on Symptom Severity

For Severe Symptomatic Hyponatremia (EMERGENCY)

Administer 3% hypertonic saline immediately 1, 2:

• Give 100 mL bolus over 10 minutes, can repeat up to 3 times at 10-minute intervals 1
• Target: Increase sodium by 6 mmol/L over first 6 hours OR until severe symptoms resolve 1, 4
• Critical limit: Do NOT exceed 8 mmol/L correction in 24 hours 1, 4, 5

Monitor serum sodium every 2 hours during initial correction 1

Discontinue 3% saline when 4:

• Severe symptoms resolve, OR
• 6 mmol/L increase achieved, OR
• Sodium reaches 131 mmol/L 4

After symptom resolution, transition to 4:

• Fluid restriction 1 L/day 4
• Monitor sodium every 4 hours instead of every 2 hours 4
• If initial 6 mmol/L corrected in first 6 hours, allow only 2 mmol/L additional correction in next 18 hours 4

For Asymptomatic or Mildly Symptomatic Hyponatremia

Treatment based on volume status 1:

Hypovolemic hyponatremia 1:

• Discontinue diuretics immediately 1
• Administer isotonic (0.9%) saline for volume repletion 1
• Correction rate: 4-8 mmol/L per day, maximum 8 mmol/L in 24 hours 1

Euvolemic hyponatremia (SIADH) 1:

• First-line: Fluid restriction to 1 L/day 1, 2
• If no response: Add oral sodium chloride 100 mEq three times daily 1, 6
• Consider urea or vaptans for resistant cases 1, 2

Hypervolemic hyponatremia (heart failure, cirrhosis) 1:

• Fluid restriction to 1-1.5 L/day 1
• Discontinue diuretics temporarily if sodium <125 mmol/L 1
• For cirrhosis: Consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms present - it worsens edema and ascites 1

Critical Correction Rate Guidelines

Standard correction limits 1, 5:

• Maximum: 8 mmol/L in 24 hours for all patients 1, 4
• Never exceed: 10 mmol/L in 24 hours 5

High-risk patients require slower correction (4-6 mmol/L per day) 1, 5:

• Advanced liver disease 1
• Alcoholism or malnutrition 1, 5
• Serum sodium <115 mmol/L 5
• Hypokalemia 5
• Prior encephalopathy 1

At sodium 115 mmol/L with high-risk features, limit correction to <8 mmol/L in 24 hours 5 - this patient population has developed osmotic demyelination syndrome even with corrections ≤10 mmol/L per day 5.

Monitoring Protocol

During active correction 1:

• Severe symptoms: Check sodium every 2 hours 1
• After symptom resolution: Check every 4 hours 1, 4
• Mild symptoms: Check every 4-6 hours initially 1

Calculate sodium deficit 1:

• Formula: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1

Management of Overcorrection

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

• Immediately discontinue current fluids 1
• Switch to D5W (5% dextrose in water) to relower sodium 1
• Consider desmopressin to slow or reverse rapid rise 1

Common Pitfalls to Avoid

Never use fluid restriction as initial treatment for severe symptomatic hyponatremia - this is a medical emergency requiring hypertonic saline 1, 4

Do not use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms - it worsens fluid overload 1

Avoid overly rapid correction - osmotic demyelination syndrome can occur even with corrections ≤10 mmol/L per day in high-risk patients with sodium <115 mmol/L 5

In neurosurgical patients, distinguish SIADH from cerebral salt wasting - CSW requires volume replacement, NOT fluid restriction 1

Monitor for osmotic demyelination syndrome - symptoms typically appear 2-7 days after rapid correction and include dysarthria, dysphagia, oculomotor dysfunction, quadriparesis 1

Special Considerations

Mortality risk: Sodium <115 mmol/L carries 60-fold increased mortality (11.2% vs 0.19%) compared to normal sodium 1 - aggressive but controlled correction is warranted.

Acute vs chronic hyponatremia 7:

• Acute (<48 hours): Can tolerate faster correction without osmotic demyelination risk 7
• Chronic (>48 hours): Requires strict adherence to 8 mmol/L per 24-hour limit 7

For cirrhotic patients: Hyponatremia increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1 - correction improves outcomes but must be cautious (4-6 mmol/L per day) 1.