What is the treatment for an adult patient with hyponatremia, particularly those with euvolemic or hypervolemic hyponatremia, severe hyponatremia, or underlying conditions such as heart failure or liver disease?

Treatment of Hyponatremia

Immediate Assessment: Symptom Severity Determines Urgency

For severe symptomatic hyponatremia (seizures, coma, altered mental status, cardiorespiratory distress), 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. 1, 2, 3

• Severe symptoms require ICU admission with cardiac monitoring and serum sodium checks every 2 hours during initial correction 1, 4
• Administer 3% hypertonic saline as 100 mL boluses over 10 minutes, repeatable up to three times at 10-minute intervals until symptoms improve 1
• Never exceed 8 mmol/L total correction in 24 hours to prevent osmotic demyelination syndrome (ODS), regardless of symptom severity 1, 2, 4

For mild to moderate symptoms (nausea, headache, confusion) or asymptomatic patients, treatment is based on volume status and underlying cause, with slower correction rates 1, 3

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Critical Safety Rule: Correction Rate Limits

The single most important principle: limit correction to maximum 8 mmol/L in 24 hours for all patients, with high-risk patients requiring even slower rates of 4-6 mmol/L per day. 1, 2, 4

• High-risk populations include: advanced liver disease, alcoholism, malnutrition, prior encephalopathy, severe hyponatremia (<120 mmol/L), hypokalemia, or hypophosphatemia 1, 5
• Monitor sodium every 2 hours during active correction for severe symptoms, every 4 hours after symptom resolution 1
• If overcorrection occurs (>8 mmol/L in 24 hours), immediately switch to D5W and consider desmopressin to relower sodium 1, 6

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Treatment Algorithm Based on Volume Status

Hypovolemic Hyponatremia (Dehydration, Diuretic Use)

Discontinue diuretics immediately and administer isotonic saline (0.9% NaCl) for volume repletion. 1, 3

• Initial infusion rate: 15-20 mL/kg/h, then 4-14 mL/kg/h based on clinical response 1
• Urine sodium <30 mmol/L predicts good response to saline (71-100% positive predictive value) 1
• Look for clinical signs: orthostatic hypotension, dry mucous membranes, decreased skin turgor, flat neck veins 1
• Once euvolemic, switch to maintenance isotonic fluids at 30 mL/kg/day 1

Euvolemic Hyponatremia (SIADH)

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

• If no response to fluid restriction after 24-48 hours, add oral sodium chloride 100 mEq (2.3 grams) three times daily 1
• For resistant cases, consider vasopressin receptor antagonists (tolvaptan 15 mg once daily, titrate to 30-60 mg) 1, 2
• Alternative options include urea, demeclocycline, or lithium, though these have more side effects 1, 2
• Critical distinction: In neurosurgical patients, differentiate SIADH from cerebral salt wasting (CSW)—CSW requires volume replacement, NOT fluid restriction 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L and treat the underlying condition. 1, 3, 5

• Temporarily discontinue diuretics if sodium <125 mmol/L 1, 5
• For cirrhotic patients, consider albumin infusion alongside fluid restriction 1, 5
• Avoid hypertonic saline unless life-threatening symptoms present—it worsens ascites and edema 1, 5
• In cirrhosis, sodium restriction (not fluid restriction) drives weight loss, as fluid follows sodium 1
• For heart failure patients with persistent severe hyponatremia despite fluid restriction, consider short-term vaptans 1

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Special Population Considerations

Liver Disease/Cirrhosis

Patients with cirrhosis require the most cautious correction: 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours, due to extremely high ODS risk. 1, 5

• Hyponatremia in cirrhosis increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
• Tolvaptan carries higher gastrointestinal bleeding risk in cirrhosis (10% vs 2% placebo) 1
• Fluid restriction alone rarely improves sodium significantly—compliance is poor and efficacy limited 1, 5

Neurosurgical Patients (Subarachnoid Hemorrhage, Brain Injury)

Distinguish cerebral salt wasting (CSW) from SIADH—they require opposite treatments. 1

• CSW: Treat with volume and sodium replacement (isotonic or hypertonic saline), fludrocortisone 0.1-0.2 mg daily for severe cases 1
• Never use fluid restriction in CSW or subarachnoid hemorrhage patients at risk of vasospasm—this worsens outcomes 1
• Consider hydrocortisone to prevent natriuresis in subarachnoid hemorrhage 1
• CSW characteristics: true hypovolemia, CVP <6 cm H₂O, high urine sodium despite volume depletion 1

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Common Pitfalls to Avoid

• Overly rapid correction (>8 mmol/L in 24 hours) causes osmotic demyelination syndrome—a devastating, potentially irreversible neurological complication 1, 2, 4
• Using fluid restriction in CSW worsens outcomes and increases cerebral ischemia risk 1
• Ignoring mild hyponatremia (130-135 mmol/L)—even mild cases increase fall risk (21% vs 5%), fractures, and mortality 1, 2
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms worsens fluid overload 1
• Inadequate monitoring during correction—check sodium every 2-4 hours initially to catch overcorrection early 1
• Failing to identify and treat underlying cause—hyponatremia is usually a symptom, not a primary disease 1

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Monitoring and Follow-up

• Severe symptoms: Check sodium every 2 hours during initial correction 1
• After symptom resolution: Check every 4 hours until stable 1
• Asymptomatic/mild symptoms: Check every 24-48 hours initially 1
• Watch for ODS signs 2-7 days post-correction: dysarthria, dysphagia, oculomotor dysfunction, quadriparesis 1
• Track daily weights in hypervolemic patients: target 0.5 kg/day loss without peripheral edema 1