What is the appropriate treatment for a patient with hyponatremia?

Treatment of Hyponatremia

For hyponatremia, treatment depends critically on symptom severity, volume status, and correction rate limits—with severe symptomatic cases requiring immediate 3% hypertonic saline to correct 6 mmol/L over 6 hours, while chronic asymptomatic cases need fluid restriction and cautious correction never exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Classification

Determine symptom severity first, as this dictates urgency and treatment approach:

• Severe symptoms (seizures, coma, altered mental status, cardiorespiratory distress) require emergency treatment regardless of sodium level 1, 2
• Moderate symptoms (nausea, vomiting, confusion, headache) warrant hospital admission and monitored correction 1
• Mild/asymptomatic cases allow outpatient management with underlying cause treatment 1

Assess volume status through physical examination, though recognize this has poor accuracy (sensitivity 41%, specificity 80%) 1:

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

Obtain essential labs before treatment: serum osmolality, urine osmolality, urine sodium, serum creatinine, TSH, and cortisol to exclude pseudohyponatremia and identify underlying causes 1

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

Administer 3% hypertonic saline immediately with target correction of 6 mmol/L over 6 hours or until severe symptoms resolve 1, 2:

• Give 100-150 mL boluses over 10 minutes, repeatable up to 3 times at 10-minute intervals 1
• Monitor serum sodium every 2 hours during initial correction 1, 2
• Total correction must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome 1, 2
• Once 6 mmol/L corrected in first 6 hours, only 2 mmol/L additional correction allowed in next 18 hours 1

For seizures specifically, use hypertonic saline as primary treatment with anticonvulsants as adjunctive therapy only—never use anticonvulsants alone 1. Avoid phenytoin in subarachnoid hemorrhage patients as it increases mortality 1.

Asymptomatic or Mildly Symptomatic Hyponatremia

Treatment depends on volume status:

Hypovolemic Hyponatremia

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 response 1
• Urine sodium <30 mmol/L predicts good response to saline (positive predictive value 71-100%) 1
• Discontinue diuretics immediately if sodium <125 mmol/L 1
• Continue until euvolemia achieved, then reassess 1

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is first-line treatment 1, 2, 4:

• If no response after 24-48 hours, add oral sodium chloride 100 mEq (approximately 6 grams) three times daily 1
• Second-line options for refractory cases: urea 15-30 grams twice daily or tolvaptan 15 mg once daily (titrate to 30-60 mg) 1, 5
• Demeclocycline and lithium are less commonly used due to side effects 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

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

• Temporarily discontinue diuretics if sodium <125 mmol/L 1
• For cirrhotic patients, consider albumin infusion (8 g per liter of ascites removed) alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens edema and ascites 1
• Treat underlying condition (optimize heart failure therapy, manage cirrhosis) 1, 4

Critical Correction Rate Guidelines

The single most important safety principle: never exceed 8 mmol/L correction in 24 hours 1, 2, 6:

• Standard correction rate: 4-8 mmol/L per day, maximum 10-12 mmol/L in 24 hours 1
• High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy, severe hyponatremia <120 mmol/L): limit to 4-6 mmol/L per day, maximum 8 mmol/L in 24 hours 1, 2

If overcorrection occurs (>8 mmol/L in 24 hours):

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

Special Populations and Considerations

Neurosurgical Patients

Distinguish between SIADH and cerebral salt wasting (CSW), as treatments are opposite 1, 2:

• SIADH: euvolemic, treat with fluid restriction 2
• CSW: hypovolemic (CVP <6 cm H₂O), treat with volume and sodium replacement using isotonic or hypertonic saline 1, 2
• Never use fluid restriction in CSW—this worsens outcomes 1, 2

For subarachnoid hemorrhage patients at risk of vasospasm:

• Avoid fluid restriction 1, 2
• Consider fludrocortisone 0.1-0.2 mg daily to prevent vasospasm 1, 2
• Hydrocortisone may prevent natriuresis 1, 2

Cirrhotic Patients

Require more cautious correction (4-6 mmol/L per day maximum) due to higher osmotic demyelination risk 1:

• Hyponatremia in cirrhosis increases risk of spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36) 1
• Fluid restriction may prevent further decline but rarely improves sodium significantly 1
• Sodium restriction, not fluid restriction, results in weight loss as fluid follows sodium 1

Medication-Induced Hyponatremia

Review and discontinue offending medications when possible 1:

• Common culprits: SSRIs, carbamazepine, NSAIDs, thiazide diuretics, opioids, chemotherapy agents 1
• For diuretic-induced hyponatremia with sodium 126-135 mmol/L and normal creatinine, continue diuretics with close monitoring 1
• Stop diuretics if sodium ≤120 mmol/L 1

Monitoring Requirements

Frequency of sodium monitoring depends on severity 1:

• Severe symptoms: every 2 hours during initial correction 1, 2
• Mild symptoms: every 4 hours after symptom resolution 1
• Asymptomatic chronic: every 24-48 hours initially 1

Watch for osmotic demyelination syndrome (typically 2-7 days after rapid correction): dysarthria, dysphagia, oculomotor dysfunction, quadriparesis 1, 2

Common Pitfalls to Avoid

Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours—this causes osmotic demyelination syndrome, which can result in permanent neurological disability or death 1, 2, 6

Never use fluid restriction in cerebral salt wasting—this worsens outcomes and can precipitate cerebral ischemia 1, 2

Never ignore mild hyponatremia (130-135 mmol/L)—even mild chronic hyponatremia increases fall risk (21% vs 5%), fracture risk, and mortality (60-fold increase with sodium <130 mmol/L) 1, 6

Never use hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms—it worsens fluid overload 1

Never fail to identify and treat the underlying cause—symptomatic treatment alone is insufficient 1, 4

Never use hypotonic fluids (lactated Ringer's, 0.45% saline) in SIADH—these worsen hyponatremia through dilution 1