What is the management for a patient with severe hyponatremia (sodium level of 126 mmol/L)?

Management of Hyponatremia at Sodium 126 mmol/L

For a patient with sodium 126 mmol/L, the choice between IV fluid versus IV sodium depends entirely on volume status: give isotonic saline (0.9% NaCl) for hypovolemic hyponatremia, implement fluid restriction for euvolemic hyponatremia (SIADH), and use fluid restriction with possible albumin for hypervolemic hyponatremia—never use hypertonic (3%) saline unless the patient has severe neurological symptoms like seizures or altered mental status. 1

Initial Assessment: Determine Volume Status

The critical first step is assessing whether the patient is hypovolemic, euvolemic, or hypervolemic, as this dictates completely opposite treatments 1, 2:

• Hypovolemic signs: Orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins 1
• Euvolemic signs: Normal volume status, no edema, no orthostasis 1
• Hypervolemic signs: Peripheral edema, ascites, jugular venous distention, pulmonary congestion 1

Check urine sodium to confirm volume status: <30 mmol/L suggests hypovolemia (71-100% positive predictive value for saline responsiveness), while >20-40 mmol/L with high urine osmolality (>300 mOsm/kg) suggests SIADH 1, 2

Treatment Algorithm Based on Volume Status

Hypovolemic Hyponatremia: Give IV Isotonic Saline

If the patient is truly volume depleted, administer 0.9% normal saline (isotonic saline, NOT hypertonic saline) for volume repletion 1, 3:

• Initial infusion rate: 15-20 mL/kg/h, then 4-14 mL/kg/h based on response 1
• Discontinue any diuretics immediately 1
• Monitor sodium every 4-6 hours initially 1
• Maximum correction: 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 4

Euvolemic Hyponatremia (SIADH): Fluid Restriction, NOT IV Fluids

For SIADH, the cornerstone of treatment is fluid restriction to 1 L/day—giving IV fluids will worsen hyponatremia 1, 2:

• Restrict fluids to 1000 mL/day 1
• If no response after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1, 5
• Consider high protein diet to augment solute intake 5
• Never give normal saline to euvolemic patients—it will worsen hyponatremia 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis): Fluid Restriction

For patients with volume overload, implement strict fluid restriction and avoid IV saline 1, 3:

• Fluid restriction to 1000-1500 mL/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 present—it worsens edema and ascites 1

When to Use Hypertonic (3%) Saline: Only for Severe Symptoms

Hypertonic saline is reserved ONLY for severe symptomatic hyponatremia with neurological emergencies 1, 4, 2:

• Indications: Seizures, coma, altered mental status, severe confusion 1, 6
• Dose: 100 mL bolus of 3% saline over 10 minutes, can repeat up to 3 times 1
• Target: Correct 6 mmol/L over first 6 hours or until symptoms resolve 1, 5
• Maximum: Never exceed 8 mmol/L correction in 24 hours (10 mmol/L absolute maximum per FDA) 1, 4

Critical Correction Rate Guidelines

The single most important safety principle: never correct chronic hyponatremia faster than 8 mmol/L in 24 hours 1, 4, 7:

• Standard rate: 4-8 mmol/L per day 1
• High-risk patients (cirrhosis, alcoholism, malnutrition, sodium <115 mmol/L): limit to 4-6 mmol/L per day 1, 7
• Exceeding 8 mmol/L in 24 hours risks osmotic demyelination syndrome—a devastating complication causing dysarthria, dysphagia, quadriparesis, or death 1, 4, 7

Monitoring Requirements

• Check sodium every 2 hours if using hypertonic saline for severe symptoms 1
• Check sodium every 4-6 hours during initial correction with isotonic saline 1, 5
• Once stable, check daily 1
• Watch for signs of osmotic demyelination syndrome 2-7 days after correction: dysarthria, dysphagia, oculomotor dysfunction, quadriparesis 1

Common Pitfalls to Avoid

• Never give normal saline to euvolemic (SIADH) or hypervolemic patients—it worsens hyponatremia 1
• Never use hypertonic saline for asymptomatic hyponatremia—it's only for neurological emergencies 1, 4
• Never correct faster than 8 mmol/L in 24 hours—osmotic demyelination syndrome is irreversible 1, 4, 7
• Never use fluid restriction in hypovolemic patients—they need volume repletion 1
• In neurosurgical patients, distinguish SIADH from cerebral salt wasting—they require opposite treatments 1