How to manage severe hyponatremia?

Management of Severe Hyponatremia (Sodium 115 mEq/L)

For a patient with sodium 115 mEq/L, immediately administer 100 mL of 3% hypertonic saline IV over 10 minutes, targeting a correction of 6 mmol/L over the first 6 hours or until severe symptoms resolve, with a strict maximum correction limit of 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1, 2

Immediate Emergency Management

• Administer 3% hypertonic saline as 100 mL boluses over 10 minutes, repeating every 10 minutes if severe symptoms persist, up to three total boluses 2
• Target an initial sodium increase of 4-6 mEq/L in the first hour to abort life-threatening cerebral edema 2
• If the patient has seizures, confusion, coma, or cardiorespiratory distress, this is a medical emergency requiring ICU admission 1, 2
• Never delay treatment while pursuing diagnostic workup—begin hypertonic saline immediately for severe symptoms 1

Critical Correction Rate Guidelines

The correction rate is the single most important safety consideration to prevent osmotic demyelination syndrome:

• Maximum correction: 8 mmol/L in 24 hours for all patients 1, 2
• Initial target: 6 mmol/L over the first 6 hours OR until severe symptoms resolve 1, 2
• If 6 mmol/L is corrected in 6 hours, only 2 mmol/L additional correction is permitted in the remaining 18 hours 2
• For high-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy), limit correction to 4-6 mmol/L per day 1

Intensive Monitoring Protocol

• Check serum sodium every 2 hours during active correction 1, 2
• Monitor strict intake and output, daily weights 2
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1
• Once severe symptoms resolve, switch to checking sodium every 4 hours 1

Determining Underlying Etiology During Acute Management

While treating, obtain the following to guide subsequent management:

• Assess extracellular fluid volume status (orthostatic hypotension, dry mucous membranes, skin turgor for hypovolemia; edema, ascites, JVD for hypervolemia) 1, 2
• Serum and urine osmolality 1, 2
• Urine sodium concentration 1, 2
• Serum uric acid (< 4 mg/dL suggests SIADH with 73-100% positive predictive value) 1
• Urine sodium < 30 mmol/L predicts response to normal saline with 71-100% positive predictive value 1

Post-Acute Management Based on Etiology

For SIADH (Euvolemic Hyponatremia)

• Fluid restriction to 1 L/day is the cornerstone of treatment 1, 2
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction 1, 2
• Consider vaptans (tolvaptan 15 mg once daily) for resistant cases, but monitor closely to avoid overcorrection 1

For Cerebral Salt Wasting (Common in Neurosurgical Patients)

• Volume and sodium replacement with isotonic or hypertonic saline—NOT fluid restriction 1, 2
• For severe symptoms, continue 3% hypertonic saline plus fludrocortisone 1, 2, 3
• Evidence of volume depletion (hypotension, tachycardia, dry mucous membranes) distinguishes CSW from SIADH 1, 3

For Hypovolemic Hyponatremia

• Discontinue diuretics immediately 1
• Administer isotonic (0.9%) saline for volume repletion 1
• Once euvolemic, reassess sodium levels 1

For Hypervolemic Hyponatremia (Cirrhosis, Heart Failure)

• Fluid restriction to 1-1.5 L/day 1
• Temporarily discontinue diuretics if sodium < 125 mmol/L 1
• Consider albumin infusion in cirrhotic patients 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens fluid overload 1

Common Pitfalls to Avoid

• Overcorrection exceeding 8 mmol/L in 24 hours causes osmotic demyelination syndrome—this is irreversible and potentially fatal 1, 2, 4
• Using fluid restriction in cerebral salt wasting worsens outcomes 1, 2
• Inadequate monitoring during active correction leads to overcorrection 1
• Failing to distinguish SIADH from cerebral salt wasting results in opposite and harmful treatments 1, 2, 3
• Ignoring high-risk populations (liver disease, alcoholism, malnutrition) who require slower correction rates 1

Management of Overcorrection

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

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse the rapid rise 1
• Target relowering to bring total 24-hour correction to no more than 8 mmol/L from baseline 1

Calculating Sodium Deficit

Use the formula: Sodium deficit = Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1

This helps determine the appropriate volume of hypertonic saline needed, though clinical monitoring supersedes calculations 1