What is the best management strategy for a patient with symptomatic hyponatremia?

Management of Hyponatremia

Immediate Assessment: Determine Symptom Severity and Acuity

For severe symptomatic hyponatremia (seizures, altered mental status, coma), immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until symptoms resolve—this is a medical emergency requiring ICU-level monitoring. 1

• Severe symptoms mandate hypertonic saline, not fluid restriction 1
• Administer 3% saline as 100-150 mL IV boluses over 10 minutes, repeatable up to 3 times at 10-minute intervals until symptoms improve 2, 3
• Monitor serum sodium every 2 hours during initial correction 1
• Never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome 1, 2, 3

For asymptomatic or mildly symptomatic hyponatremia, proceed with diagnostic workup before initiating specific therapy 1, 4

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Diagnostic Workup: Establish Volume Status and Etiology

Obtain serum osmolality, urine osmolality, and urine sodium concentration to determine the underlying cause 1, 4

Volume Status Assessment

• Hypovolemic signs: orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins 1
• Euvolemic signs: normal volume status without edema or dehydration 1
• Hypervolemic signs: peripheral edema, ascites, jugular venous distention, pulmonary congestion 1

Key Laboratory Interpretation

• Urine sodium <30 mmol/L suggests hypovolemic hyponatremia responsive to saline (71-100% positive predictive value) 1
• Urine sodium >20-40 mmol/L with urine osmolality >300 mOsm/kg suggests SIADH 1, 4
• Serum uric acid <4 mg/dL has 73-100% positive predictive value for SIADH 1

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Treatment Algorithm Based on Volume Status

Hypovolemic Hyponatremia

Administer isotonic saline (0.9% NaCl) for volume repletion at 15-20 mL/kg/h initially, then 4-14 mL/kg/h based on response. 1

• Discontinue diuretics immediately if sodium <125 mmol/L 1
• For cirrhotic patients, consider albumin infusion alongside isotonic saline 1
• Correction rate: 4-6 mmol/L per day maximum for high-risk patients (cirrhosis, alcoholism, malnutrition) 1

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of SIADH treatment. 1, 2, 3

• If no response to fluid restriction after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1, 5
• For persistent hyponatremia despite fluid restriction, consider urea or tolvaptan 15 mg once daily 1, 2
• Critical distinction: In neurosurgical patients, differentiate SIADH from cerebral salt wasting (CSW)—CSW requires volume and sodium replacement, NOT fluid restriction 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L. 1, 3

• Temporarily discontinue diuretics if sodium <125 mmol/L 1
• For cirrhotic patients, consider albumin infusion (6-8 g per liter of ascites drained) 1
• Avoid hypertonic saline unless life-threatening symptoms are present—it worsens ascites and edema 1
• Tolvaptan may be considered for persistent severe hyponatremia despite fluid restriction, but use with extreme caution in cirrhosis due to 10% risk of gastrointestinal bleeding (vs. 2% placebo) 6

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Critical Correction Rate Guidelines

The maximum correction rate is 8 mmol/L in 24 hours for all patients. 1, 2, 3

• For high-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy), limit to 4-6 mmol/L per day 1
• Calculate sodium deficit: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1, 5
• For severe symptoms, correct 6 mmol/L in first 6 hours, then only 2 mmol/L additional in next 18 hours 1

Monitoring Frequency

• Severe symptoms: check sodium every 2 hours initially 1
• Mild symptoms: check sodium every 4-6 hours during initial correction 1, 5
• After symptom resolution: check sodium every 24-48 hours 1

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Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours, immediately intervene to prevent osmotic demyelination syndrome 1, 7

• Discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Administer desmopressin 1-2 µg parenterally to slow or reverse rapid rise 1, 7
• Target relowering to bring total 24-hour correction to ≤8 mmol/L from starting point 1

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Special Population Considerations

Neurosurgical Patients (Subarachnoid Hemorrhage, Brain Injury)

Distinguish cerebral salt wasting from SIADH—treatment approaches are opposite. 1

• CSW characteristics: true hypovolemia, CVP <6 cm H₂O, urine sodium >20 mmol/L despite volume depletion 1
• CSW treatment: volume and sodium replacement with isotonic or hypertonic saline, fludrocortisone 0.1-0.2 mg daily for severe symptoms 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm—it worsens outcomes 1

Cirrhotic Patients

Hyponatremia in cirrhosis increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1

• Correction rate must not exceed 4-6 mmol/L per day due to high osmotic demyelination risk 1
• Sodium restriction (not fluid restriction) results in weight loss as fluid follows sodium 1
• Reserve hypertonic saline only for life-threatening symptoms or pre-transplant patients 1

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Common Pitfalls to Avoid

• Never use fluid restriction as initial treatment for altered mental status—this requires hypertonic saline 1
• Never exceed 8 mmol/L correction in 24 hours—overcorrection causes osmotic demyelination syndrome 1, 2, 3
• Never use fluid restriction in cerebral salt wasting—it worsens outcomes 1
• Never ignore mild hyponatremia (130-135 mmol/L)—it increases fall risk (21% vs. 5%) and mortality (60-fold increase with sodium <130 mmol/L) 1
• Never use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms—it worsens fluid overload 1