How to treat hyponatremia?

Treatment of Hyponatremia

The treatment of hyponatremia depends critically on volume status (hypovolemic, euvolemic, or hypervolemic), symptom severity, and chronicity, with the overriding principle being to avoid correction exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Classification

Determine volume status through physical examination looking for orthostatic hypotension, dry mucous membranes, skin turgor (hypovolemic); jugular venous distention, peripheral edema, ascites (hypervolemic); or absence of these findings (euvolemic). 1

• Obtain serum and urine osmolality, urine sodium, and urine electrolytes to determine the underlying cause. 1
• Treatment should be initiated when serum sodium is <130-135 mmol/L, though even mild hyponatremia (130-135 mmol/L) increases fall risk and mortality and should not be ignored. 1, 2
• Classify severity: mild (130-134 mmol/L), moderate (125-129 mmol/L), severe (<125 mmol/L). 3

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

For patients with severe symptoms (seizures, coma, confusion, obtundation, cardiorespiratory distress), immediately administer 3% hypertonic saline with a goal to increase sodium by 4-6 mmol/L over the first 6 hours or until symptoms resolve. 1, 2, 3

• Give 3% hypertonic saline as 100 mL boluses over 10 minutes, repeatable up to three times at 10-minute intervals until symptoms improve. 1
• Total correction must not exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1, 2
• Monitor serum sodium every 2 hours during initial correction. 1
• Consider ICU admission for close monitoring. 1

Asymptomatic or Mildly Symptomatic Hyponatremia

Treatment is based on volume status:

Treatment Based on Volume Status

Hypovolemic Hyponatremia

Discontinue diuretics immediately and administer isotonic saline (0.9% NaCl) for volume repletion. 4, 1

• This is typically caused by excessive diuretic use, gastrointestinal losses, or severe burns. 5
• Urine sodium <30 mmol/L suggests hypovolemic hyponatremia and predicts response to saline infusion. 1
• Once euvolemic, reassess and adjust management accordingly. 1

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of treatment for SIADH. 1, 5

• If fluid restriction fails, add oral sodium chloride 100 mEq three times daily. 1
• For resistant cases, consider vaptans (tolvaptan 15 mg daily, titrate to 30-60 mg) which selectively block V2-receptors of vasopressin. 4, 6
• Alternative options include urea, demeclocycline, or lithium, though these have more side effects. 1, 5
• Do not use fluid restriction in cerebral salt wasting (CSW), which requires volume and sodium replacement instead. 1

Hypervolemic Hyponatremia (Cirrhosis, Heart Failure)

Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L. 4, 1

• Discontinue diuretics temporarily if sodium <125 mmol/L. 1
• In cirrhotic patients, consider albumin infusion to improve serum sodium concentration. 4, 1
• Avoid hypertonic saline unless life-threatening symptoms are present, as it worsens ascites and edema. 4, 1
• Vaptans may be considered for clinically significant hyponatremia resistant to fluid restriction, starting with tolvaptan 15 mg once daily. 4, 6
• Note that fluid restriction prevents further sodium decrease but rarely improves it significantly; it is sodium restriction, not fluid restriction, that results in weight loss as fluid passively follows sodium. 1

Correction Rate Guidelines

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

• For high-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy), limit correction to 4-6 mmol/L per day. 1
• For chronic hyponatremia, avoid correction exceeding 1 mmol/L per hour. 4
• Calculate sodium deficit using: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg). 1

Management of Overcorrection

If sodium correction exceeds 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 the rapid rise in serum sodium. 1
• Watch for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction. 1

Special Populations

Neurosurgical Patients

Distinguish between SIADH and cerebral salt wasting (CSW), as treatment approaches differ fundamentally. 1

• CSW requires volume and sodium replacement with isotonic or hypertonic saline, NOT fluid restriction. 1
• Consider fludrocortisone for hyponatremia in subarachnoid hemorrhage patients at risk of vasospasm. 1
• Do not use fluid restriction in subarachnoid hemorrhage patients at risk of vasospasm. 1

Cirrhotic Patients

Patients with cirrhosis and hyponatremia have increased risk of complications: spontaneous bacterial peritonitis (OR 3.40), hepatorenal syndrome (OR 3.45), and hepatic encephalopathy (OR 2.36). 1

• These patients require more cautious correction rates (4-6 mmol/L per day). 1
• Tolvaptan carries higher risk of gastrointestinal bleeding in cirrhosis (10% vs 2% placebo). 1

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours leading to osmotic demyelination syndrome. 1
• Using fluid restriction in cerebral salt wasting, which worsens outcomes. 1
• Inadequate monitoring during active correction. 1
• Failing to recognize and treat the underlying cause. 1
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms. 4, 1
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant. 1, 2