How to manage a patient with severe hyponatremia?

Management of Severe Hyponatremia (Sodium 125 mmol/L)

For a patient with severe hyponatremia (sodium 125 mmol/L), immediately assess symptom severity and volume status to determine treatment urgency—severely symptomatic patients require emergency 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours, while asymptomatic or mildly symptomatic patients should receive treatment based on volume status (isotonic saline for hypovolemia, fluid restriction for euvolemia/hypervolemia), with correction never exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Immediate Assessment Required

Symptom Severity Classification

• Severe symptoms (requiring emergency treatment): seizures, coma, altered mental status, confusion, obtundation, cardiorespiratory distress 1, 2
• Mild symptoms: nausea, vomiting, weakness, headache, mild neurocognitive deficits 2, 3
• Asymptomatic: no neurological symptoms but still at risk for falls (21% vs 5% in normonatremic patients) and increased mortality (60-fold increase with sodium <130 mmol/L) 1, 2

Volume Status Determination

• Hypovolemic signs: orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins 1
• Euvolemic signs: no edema, normal blood pressure, moist mucous membranes 1
• Hypervolemic signs: peripheral edema, ascites, jugular venous distention, pulmonary congestion 1

Emergency Treatment for Severe Symptoms

Administer 3% hypertonic saline immediately if patient has seizures, coma, or severe neurological symptoms 1, 2, 3

• Initial bolus: 100 mL of 3% saline over 10 minutes, can repeat up to 3 times at 10-minute intervals until symptoms improve 1
• Target correction: 6 mmol/L over first 6 hours or until severe symptoms resolve 1
• Maximum limit: Total correction must not exceed 8 mmol/L in 24 hours 1, 4, 2
• Monitoring: Check serum sodium every 2 hours during initial correction 1
• Hospital admission required: Patients must be hospitalized for initiation of therapy to monitor for osmotic demyelination syndrome 4

Treatment Based on Volume Status (Non-Emergency)

Hypovolemic Hyponatremia

• Discontinue diuretics immediately 1
• 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
• Predictive indicator: Urine sodium <30 mmol/L predicts 71-100% response to saline infusion 1
• Avoid hypotonic fluids (including lactated Ringer's) as they can worsen hyponatremia 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day is the cornerstone of treatment 1, 2
• Add oral sodium chloride 100 mEq three times daily if no response to fluid restriction 1
• Consider vaptans (tolvaptan 15 mg once daily, titrate to 30-60 mg) for resistant cases, but use with caution due to risk of overly rapid correction 1, 4, 2
• Alternative agents: Urea, demeclocycline, or lithium for persistent cases 1, 2

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1, 3
• Discontinue diuretics temporarily until sodium improves 1
• For cirrhotic patients: Consider albumin infusion (6-8 g per liter of ascites drained) alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens ascites and edema 1
• Sodium restriction (not fluid restriction) results in weight loss as fluid follows sodium 1

Critical Correction Rate Guidelines

Never exceed 8 mmol/L correction in 24 hours to prevent osmotic demyelination syndrome 1, 4, 2, 3

Standard Correction Rates

• Average risk patients: 4-8 mmol/L per day, maximum 10-12 mmol/L in 24 hours 1
• High-risk patients: 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours 1

High-Risk Populations Requiring Slower Correction

• Advanced liver disease 1, 2
• Alcoholism or malnutrition 1, 2
• Severe hyponatremia (<120 mmol/L) 1
• Prior encephalopathy 1
• Hypophosphatemia, hypokalemia, hypoglycemia 1

Essential Diagnostic Workup

• Serum osmolality: Exclude pseudohyponatremia (normal 275-290 mOsm/kg) 1
• Urine osmolality and sodium: Differentiate causes (SIADH shows urine sodium >20-40 mmol/L, urine osmolality >300 mOsm/kg) 1, 5
• Serum uric acid: <4 mg/dL suggests SIADH with 73-100% positive predictive value 1
• Thyroid and adrenal function: Rule out hypothyroidism and adrenal insufficiency 1
• For hypervolemic patients: Liver function tests, BNP for heart failure assessment 1

Monitoring Protocol

• Severe symptoms: Check sodium every 2 hours during initial correction 1
• Mild symptoms: Check sodium every 4 hours initially, then daily 1
• Track daily weights: Aim for 0.5 kg/day weight loss in absence of peripheral edema 1
• Watch for osmotic demyelination syndrome: Dysarthria, dysphagia, oculomotor dysfunction, quadriparesis typically occurring 2-7 days after rapid correction 1, 2

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours 1:

• Immediately discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse the rapid rise 1
• Target reduction to bring total 24-hour correction to no more than 8 mmol/L from starting point 1

Special Considerations

Neurosurgical Patients

• Distinguish cerebral salt wasting (CSW) from SIADH—treatment approaches are opposite 1
• CSW requires volume and sodium replacement, not fluid restriction 1
• For severe CSW: 3% hypertonic saline plus fludrocortisone 0.1-0.2 mg daily 1
• Never use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm 1

Cirrhotic Patients

• Hyponatremia increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
• Tolvaptan carries higher risk of gastrointestinal bleeding (10% vs 2% placebo) 1
• More cautious correction rates (4-6 mmol/L per day) required 1

Common Pitfalls to Avoid

• Never ignore mild hyponatremia (130-135 mmol/L)—it increases fall risk and mortality 1, 2
• Never use fluid restriction as initial treatment for altered mental status—this is a medical emergency requiring hypertonic saline 1
• Never use fluid restriction in cerebral salt wasting—this worsens outcomes 1
• Never exceed 8 mmol/L correction in 24 hours—overcorrection risks osmotic demyelination syndrome 1, 4, 2
• Never use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Inadequate monitoring during active correction leads to complications 1