What is the treatment for hyponatremia?

Treatment of Hyponatremia

The treatment of hyponatremia depends critically on three factors: symptom severity, volume status (hypovolemic, euvolemic, or hypervolemic), and chronicity (acute <48 hours vs. chronic >48 hours), with the overriding principle being that correction must never exceed 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment

Before initiating treatment, rapidly assess the following:

• Symptom severity: Severe symptoms (seizures, coma, altered consciousness, respiratory distress) require immediate hypertonic saline 1, 2. Mild symptoms (nausea, headache, weakness) allow for more measured correction 2, 3.

• Volume status: Examine for orthostatic hypotension, dry mucous membranes (hypovolemic); peripheral edema, ascites, jugular venous distention (hypervolemic); or absence of these findings (euvolemic) 1.

• Laboratory workup: Obtain serum and urine osmolality, urine sodium, and urine electrolytes to determine the underlying cause 1, 3.

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

For patients with seizures, coma, confusion, or altered consciousness, immediately administer 3% hypertonic saline with a target correction of 6 mmol/L over 6 hours or until severe symptoms resolve. 1, 4

• Administer 3% hypertonic saline as 100 mL boluses over 10 minutes, which can be repeated 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, 4, 5.
• Monitor serum sodium every 2 hours during initial correction 1.
• Consider ICU admission for close monitoring 1.

Asymptomatic or Mildly Symptomatic Hyponatremia

Treatment is determined by volume status and underlying etiology 1, 3.

Treatment Based on Volume Status

Hypovolemic Hyponatremia

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 response 1.
• Urine sodium <30 mmol/L predicts good response to saline infusion (positive predictive value 71-100%) 1.
• For severe dehydration with neurological symptoms, consider hypertonic saline with careful monitoring 1.
• Correction rate should not exceed 8 mmol/L in 24 hours 1, 4.

Euvolemic Hyponatremia (SIADH)

Fluid restriction to 1 L/day is the cornerstone of treatment for SIADH. 1, 4, 6

• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1.
• For persistent hyponatremia despite fluid restriction, consider vasopressin receptor antagonists (tolvaptan 15 mg once daily, titrated to 30-60 mg) 1, 7, 4.
• Alternative pharmacological options include urea, demeclocycline, or lithium for resistant cases 1, 4, 8.
• For severe symptoms, use 3% hypertonic saline with careful monitoring 1.

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

Implement fluid restriction to 1-1.5 L/day for serum sodium <125 mmol/L. 1, 3, 6

• Discontinue diuretics temporarily if sodium <125 mmol/L 1.
• In cirrhotic patients, consider albumin infusion alongside fluid restriction 1.
• Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1.
• Vasopressin receptor antagonists (tolvaptan) may be considered for persistent severe hyponatremia despite fluid restriction and maximization of guideline-directed medical therapy 1, 7.
• Manage underlying condition (heart failure, cirrhosis) as primary treatment 1, 6.

Special Considerations for Neurosurgical Patients

In neurosurgical patients, distinguish between SIADH and cerebral salt wasting (CSW), as treatment approaches are fundamentally opposite. 1

Cerebral Salt Wasting (CSW)

• Treatment focuses on volume and sodium replacement, NOT fluid restriction 1.
• Administer isotonic or hypertonic saline based on severity 1.
• For severe symptoms, use 3% hypertonic saline plus fludrocortisone (0.1-0.2 mg daily) in ICU 1.
• Consider hydrocortisone to prevent natriuresis in subarachnoid hemorrhage patients 1.
• Fluid restriction in CSW worsens outcomes 1.

Critical Correction Rate Guidelines

The maximum correction rate is 8 mmol/L in 24 hours for all patients to prevent osmotic demyelination syndrome. 1, 4, 5

High-Risk Patients Requiring Slower Correction (4-6 mmol/L per day):

• Advanced liver disease 1, 4
• Alcoholism 1, 4
• Malnutrition 1, 4
• Prior encephalopathy 1
• Severe hyponatremia (<120 mmol/L) 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.
• Monitor for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1.

Common Pitfalls to Avoid

• Never correct chronic hyponatremia faster than 8 mmol/L in 24 hours - this causes osmotic demyelination syndrome 1, 4.
• Inadequate monitoring during active correction 1.
• Using fluid restriction in cerebral salt wasting 1.
• Failing to recognize and treat the underlying cause 1.
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1.
• Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant - it increases fall risk and mortality 1, 2, 4.

Monitoring During Treatment

• Severe symptoms: Monitor serum sodium every 2 hours during initial correction 1.
• Mild symptoms: Monitor every 4 hours after resolution of severe symptoms 1.
• Continue monitoring daily to ensure correction does not exceed limits 1.
• Watch for signs of osmotic demyelination syndrome 2-7 days after correction 1.