How should hyponatremia be managed?

Management of Hyponatremia

Initial Assessment and Classification

Hyponatremia management depends critically on three factors: symptom severity, acuity of onset, and volume status. 1 Begin by determining whether the patient has severe symptoms (seizures, coma, altered consciousness), moderate symptoms (nausea, confusion, headache), or is asymptomatic. 1, 2 The rapidity of development matters enormously—acute hyponatremia (<48 hours) causes more severe symptoms at the same sodium level than chronic hyponatremia. 2

Assess volume status through physical examination, looking specifically for:

• Hypovolemic signs: orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins 1
• Hypervolemic signs: peripheral edema, ascites, jugular venous distention, pulmonary congestion 1
• Euvolemic: absence of both volume depletion and overload 1

Obtain serum and urine osmolality, urine sodium, and urine electrolytes to determine the underlying cause. 1 A urine sodium <30 mmol/L suggests hypovolemic hyponatremia responsive to saline, while >20 mmol/L with high urine osmolality suggests SIADH. 1

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

For patients with seizures, coma, or altered consciousness, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until symptoms resolve. 1 This is a true medical emergency requiring ICU-level monitoring. 1

• Give 100 mL boluses of 3% NaCl over 10 minutes, repeatable up to three times at 10-minute intervals 1
• Check serum sodium every 2 hours during initial correction 1
• Never exceed 8 mmol/L correction in any 24-hour period to prevent osmotic demyelination syndrome 1
• Once severe symptoms resolve, switch to slower correction and check sodium every 4 hours 1

Asymptomatic or Mildly Symptomatic Hyponatremia

Treatment depends on volume status:

Hypovolemic Hyponatremia:

• Discontinue diuretics immediately 1
• Administer isotonic saline (0.9% NaCl) for volume repletion 1
• Initial rate: 15-20 mL/kg/h, then 4-14 mL/kg/h based on response 1
• Target correction: 4-8 mmol/L per day, maximum 8 mmol/L in 24 hours 1

Euvolemic Hyponatremia (SIADH):

• Fluid restriction to 1 L/day is the cornerstone of treatment 1
• If no response, add oral sodium chloride 100 mEq three times daily 1
• For resistant cases, consider vasopressin receptor antagonists (tolvaptan 15 mg once daily) 1
• Avoid fluid restriction in neurosurgical patients with subarachnoid hemorrhage at risk for vasospasm 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis):

• Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
• Discontinue diuretics temporarily if sodium <125 mmol/L 1
• Consider albumin infusion in cirrhotic patients (8 g per liter of ascites removed) 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it worsens edema and ascites 1

Critical Correction Rate Guidelines

The single most important safety principle: never correct chronic hyponatremia faster than 8 mmol/L in 24 hours. 1 This limit prevents osmotic demyelination syndrome, a devastating complication causing dysarthria, dysphagia, oculomotor dysfunction, and quadriparesis. 1

For high-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy), use even more conservative rates:

• Target 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours 1
• These patients have a 0.5-1.5% risk of osmotic demyelination even with careful correction 1

If overcorrection occurs:

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

Special Populations

Neurosurgical Patients

Distinguish cerebral salt wasting (CSW) from SIADH—they require opposite treatments. 1 CSW presents with true hypovolemia (CVP <6 cm H₂O, orthostatic changes) and requires aggressive volume and sodium replacement, never fluid restriction. 1 For severe CSW, use 3% hypertonic saline plus fludrocortisone 0.1-0.2 mg daily. 1

In subarachnoid hemorrhage patients at risk for vasospasm:

• Never use fluid restriction 1
• Consider fludrocortisone to prevent vasospasm 1
• Hydrocortisone may prevent natriuresis 1

Cirrhotic Patients

Hyponatremia in cirrhosis reflects worsening hemodynamic status and increases risk of:

• Spontaneous bacterial peritonitis (OR 3.40) 1
• Hepatorenal syndrome (OR 3.45) 1
• Hepatic encephalopathy (OR 2.36) 1

Management priorities:

• Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
• Albumin infusion alongside fluid restriction 1
• Maximum correction 4-6 mmol/L per day due to exceptionally high osmotic demyelination risk 1
• Tolvaptan carries higher gastrointestinal bleeding risk (10% vs 2% placebo) and should be used cautiously 1

Common Pitfalls to Avoid

• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant—even mild chronic hyponatremia increases mortality 60-fold (11.2% vs 0.19%) and fall risk (21% vs 5%) 1, 2
• Using fluid restriction in cerebral salt wasting—this worsens outcomes and can be fatal 1
• Inadequate monitoring during active correction—check sodium every 2 hours for severe symptoms, every 4 hours after resolution 1
• Failing to recognize and treat the underlying cause while managing the sodium level 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms—this worsens fluid overload 1
• Overly rapid correction exceeding 8 mmol/L in 24 hours—this causes osmotic demyelination syndrome 1

Monitoring Requirements

For severe symptoms:

• Serum sodium every 2 hours during initial correction 1
• After symptom resolution: every 4 hours 1
• Watch for osmotic demyelination signs 2-7 days after correction (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) 1

For mild/moderate symptoms:

• Serum sodium every 4-6 hours initially 1
• Daily once stable 1