What is the initial approach to treating hyponatremia?

Initial Approach to Treating Hyponatremia

The initial approach to treating hyponatremia must prioritize determining symptom severity and volume status, as these two factors dictate whether you use hypertonic saline emergently or implement fluid restriction/volume repletion. 1

Step 1: Assess Symptom Severity Immediately

Severe symptoms (seizures, coma, altered mental status, confusion) require immediate 3% hypertonic saline—this is a medical emergency. 1, 2

• Administer 100 mL of 3% hypertonic saline IV over 10 minutes 2
• Repeat every 10 minutes if seizures persist, up to three total boluses 2
• Target correction of 6 mmol/L over 6 hours or until severe symptoms resolve 1, 2
• Never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome 1, 2

Mild/moderate symptoms (nausea, headache, weakness) or asymptomatic patients do not require hypertonic saline initially. 1, 3

Step 2: Determine Volume Status

Assess extracellular fluid volume through physical examination, looking specifically for: 1

• Hypovolemia signs: orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins 1
• Hypervolemia signs: peripheral edema, ascites, jugular venous distention, pulmonary congestion 1
• Euvolemia: absence of both hypovolemic and hypervolemic signs 1

Step 3: Obtain Essential Laboratory Tests

Order immediately (do not delay treatment while awaiting results): 1

• Serum osmolality (to exclude pseudohyponatremia) 1, 4
• Urine osmolality and urine sodium concentration 1, 4
• Serum creatinine and electrolytes 1
• Thyroid-stimulating hormone (TSH) to rule out hypothyroidism 1

Urine sodium <30 mmol/L predicts response to saline with 71-100% positive predictive value in hypovolemic hyponatremia. 1

Step 4: Treatment Based on Volume Status

For Hypovolemic Hyponatremia:

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

For Euvolemic Hyponatremia (SIADH):

• Fluid restriction to 1 L/day is the cornerstone of treatment 1, 2, 4
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1, 2
• For severe symptoms: 3% hypertonic saline with careful monitoring 1
• Consider vasopressin receptor antagonists (tolvaptan 15 mg daily) for resistant cases 1, 5

For Hypervolemic Hyponatremia (heart failure, cirrhosis):

• Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1, 4
• Discontinue diuretics temporarily if sodium <125 mmol/L 1
• Consider albumin infusion in cirrhotic patients 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens edema and ascites 1

Step 5: Critical Correction Rate Guidelines

Standard correction rate: 4-8 mmol/L per day, never exceeding 8 mmol/L in 24 hours 1, 6, 3

High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy) require slower correction: 4-6 mmol/L per day 1, 2

Step 6: Monitoring Protocol

For severe symptoms: 1, 2

• Check serum sodium every 2 hours during initial correction 1, 2
• Monitor strict intake and output 2
• Obtain daily weights 2

For mild symptoms or asymptomatic: 1

• Check serum sodium every 4-6 hours initially 1
• Adjust monitoring frequency based on response 1

Common Pitfalls to Avoid

Overcorrection exceeding 8 mmol/L in 24 hours causes osmotic demyelination syndrome—a devastating neurological complication with dysarthria, dysphagia, quadriparesis, or death. 1, 6

Using fluid restriction in cerebral salt wasting (common in neurosurgical patients) worsens outcomes—these patients need volume and sodium replacement, not restriction. 1, 2

Administering normal saline to euvolemic patients with SIADH can paradoxically worsen hyponatremia. 1

Ignoring mild hyponatremia (130-135 mmol/L) increases fall risk 21% vs 5% and mortality 60-fold (11.2% vs 0.19%). 1, 6

Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms worsens fluid overload. 1