At what sodium level is correction necessary?

Hyponatremia Requiring Correction

Hyponatremia should be evaluated and treated when serum sodium falls below 135 mmol/L, with more aggressive intervention warranted when sodium drops below 131 mmol/L, and urgent treatment required for severe symptomatic hyponatremia or levels below 125 mmol/L. 1

Threshold-Based Treatment Algorithm

Mild Hyponatremia (130-135 mmol/L)

• Do not ignore these levels - even mild hyponatremia increases fall risk (21% vs 5% in normonatremic patients) and mortality (60-fold increase when <130 mmol/L) 1
• Initiate full diagnostic workup including serum and urine osmolality, urine sodium, and volume status assessment 1
• For patients on diuretics with sodium 126-135 mmol/L and normal creatinine, continue diuretics but monitor electrolytes closely without water restriction 1

Moderate Hyponatremia (120-125 mmol/L)

• Implement fluid restriction to 1000-1500 mL/day for euvolemic or hypervolemic patients 1
• Discontinue diuretics temporarily if contributing to hyponatremia 1
• For hypervolemic states (cirrhosis, heart failure), add albumin infusion in cirrhotic patients 1
• Consider oral sodium chloride 100 mEq three times daily if fluid restriction fails in SIADH 2

Severe Hyponatremia (<120 mmol/L)

• Requires immediate intervention regardless of symptoms 1
• Stop diuretics immediately and implement volume expansion with isotonic saline for hypovolemic patients 1
• For hypervolemic patients, severe fluid restriction plus albumin infusion 1

Symptom-Driven Urgent Treatment

Severe Symptomatic Hyponatremia (Any Level)

Symptoms include: seizures, coma, altered mental status, confusion 1

• Administer 3% hypertonic saline immediately with target correction of 6 mmol/L over 6 hours or until symptoms resolve 1
• Give as 100 mL boluses over 10 minutes, repeatable up to three times at 10-minute intervals 1
• Critical safety limit: Never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome 1
• Monitor serum sodium every 2 hours during initial correction 1

Volume Status-Specific Correction Thresholds

Hypovolemic Hyponatremia

• Urine sodium <30 mmol/L predicts good response to isotonic saline (positive predictive value 71-100%) 1
• Begin isotonic saline (0.9% NaCl) for volume repletion at 15-20 mL/kg/h initially 1
• Maximum correction: 8 mmol/L per 24 hours 1

Euvolemic Hyponatremia (SIADH)

• Serum uric acid <4 mg/dL has 73-100% positive predictive value for SIADH 1
• Fluid restriction to 1 L/day is first-line treatment 1
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction 2

Hypervolemic Hyponatremia

• Fluid restriction to 1-1.5 L/day mandatory when sodium <125 mmol/L 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens edema and ascites 1
• In cirrhosis, albumin infusion alongside fluid restriction 1

High-Risk Population Adjustments

Patients with advanced liver disease, alcoholism, malnutrition, or prior encephalopathy require even more cautious correction:

• Maximum 4-6 mmol/L per day, never exceeding 8 mmol/L in 24 hours 1
• Risk of osmotic demyelination syndrome is 0.5-1.5% in liver transplant recipients 1

Neurosurgical Patient Considerations

• Cerebral salt wasting (CSW) requires fundamentally different treatment than SIADH 1
• CSW: Volume and sodium replacement with normal saline or hypertonic saline, NEVER fluid restriction 1
• Evidence of volume depletion (CVP <6 cm H₂O, hypotension, tachycardia) indicates CSW 1
• In subarachnoid hemorrhage patients at risk for vasospasm, avoid fluid restriction entirely 1
• Consider fludrocortisone 0.1-0.2 mg daily for severe CSW symptoms 1

Common Pitfalls

• Failing to recognize that sodium 130-135 mmol/L is not benign - increases mortality and fall risk 1
• Using fluid restriction in CSW worsens outcomes 1
• Inadequate monitoring during active correction leads to overcorrection 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Correcting chronic hyponatremia >8 mmol/L in 24 hours causes osmotic demyelination syndrome 1