How to manage hyponatremia (low sodium levels)?

Management of Hyponatremia

For hyponatremia management, the approach depends critically on symptom severity and volume status, with correction rates never exceeding 8 mmol/L in 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment

Begin by determining:

• Symptom severity: Severe symptoms (seizures, coma, altered mental status) versus mild/asymptomatic 1
• Volume status: Hypovolemic, euvolemic, or hypervolemic 1
• Chronicity: Acute (<48 hours) versus chronic (>48 hours) 1
• Serum sodium level: Mild (130-135 mmol/L), moderate (120-130 mmol/L), or severe (<120 mmol/L) 1

Obtain serum and urine osmolality, urine sodium, and assess extracellular fluid volume status through physical examination (orthostatic hypotension, dry mucous membranes, skin turgor, jugular venous distention, peripheral edema, ascites). 1

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Medical Emergency)

For patients with seizures, coma, or severe altered mental status, immediately administer 3% hypertonic saline. 1

• Initial goal: Correct by 6 mmol/L over 6 hours or until severe symptoms resolve 1
• Maximum correction: Never exceed 8 mmol/L in 24 hours 1, 2, 3
• Administration: Give 100 mL boluses of 3% saline over 10 minutes, repeatable up to three times at 10-minute intervals until symptoms improve 1
• Monitoring: Check serum sodium every 2 hours during initial correction 1

The evidence strongly supports this approach, with guidelines from the American Association of Neurological Surgeons and European Society of Intensive Care Medicine emphasizing that severely symptomatic hyponatremia requires rapid initial correction to prevent brain herniation, but the total 24-hour correction must remain limited to prevent osmotic demyelination syndrome. 1, 3

Mild to Moderate Symptomatic or Asymptomatic Hyponatremia

Treatment depends on volume status:

Hypovolemic Hyponatremia

• Discontinue diuretics immediately 1
• Administer isotonic saline (0.9% NaCl) for volume repletion 1
• Urine sodium <30 mmol/L predicts good response to saline (positive predictive value 71-100%) 1
• Correction rate: 4-8 mmol/L per day, not exceeding 8 mmol/L in 24 hours 1

Euvolemic Hyponatremia (SIADH)

• Fluid restriction to 1 L/day is the cornerstone of treatment 1
• If no response to fluid restriction, add oral sodium chloride 100 mEq three times daily 1
• For resistant cases, consider vasopressin receptor antagonists (tolvaptan 15 mg once daily, titrate based on response) 1, 4
• Alternative options: urea, demeclocycline, lithium, loop diuretics 1

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

• Implement fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
• Discontinue diuretics temporarily if sodium <125 mmol/L 1
• For cirrhotic patients: Consider albumin infusion alongside fluid restriction 1
• Avoid hypertonic saline unless life-threatening symptoms present, as it worsens edema and ascites 1
• Sodium restriction (not fluid restriction) results in weight loss as fluid follows sodium in cirrhotic patients 1

Critical Correction Rate Guidelines

The maximum correction rate is 8 mmol/L in 24 hours for all patients. 1, 3 However, high-risk populations require even more cautious correction:

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

Patients with the following conditions are at increased risk for osmotic demyelination syndrome and require slower correction: 1

• Advanced liver disease
• Alcoholism
• Malnutrition
• Prior encephalopathy
• Severe hyponatremia (<120 mmol/L)
• Hypokalemia
• Hypophosphatemia

The evidence for these correction rates is robust, with multiple guideline societies (American Association for the Study of Liver Diseases, European Association for the Study of the Liver, Neurosurgery society) consistently recommending these limits. 1 Research studies have demonstrated that exceeding these rates significantly increases the risk of osmotic demyelination syndrome, which can result in parkinsonism, quadriparesis, or death. 3

Special Considerations

Neurosurgical Patients: SIADH vs. Cerebral Salt Wasting (CSW)

Distinguishing between SIADH and CSW is critical because treatments are opposite. 1

SIADH characteristics:

• Euvolemic state (normal CVP)
• Urine sodium >20-40 mmol/L
• Urine osmolality >300 mOsm/kg
• Treatment: Fluid restriction 1

CSW characteristics:

• True hypovolemia (CVP <6 cm H₂O)
• Urine sodium >20 mmol/L despite volume depletion
• Evidence of extracellular volume depletion
• Treatment: Volume and sodium replacement with isotonic or hypertonic saline, NOT fluid restriction 1
• For severe symptoms: 3% hypertonic saline plus fludrocortisone in ICU 1

In subarachnoid hemorrhage patients at risk for vasospasm, never use fluid restriction. 1 Consider fludrocortisone or hydrocortisone to prevent natriuresis. 1

Cirrhotic Patients

Hyponatremia in cirrhosis carries significant prognostic implications, with sodium ≤130 mmol/L associated with increased risk of: 1

• Spontaneous bacterial peritonitis (OR 3.40)
• Hepatorenal syndrome (OR 3.45)
• Hepatic encephalopathy (OR 2.36)

Management approach:

• Fluid restriction to 1-1.5 L/day for sodium <125 mmol/L 1
• Albumin infusion may be beneficial 1
• Tolvaptan can be used but carries higher risk of gastrointestinal bleeding (10% vs 2% placebo) 1, 4
• Correction rate: 4-6 mmol/L per day maximum 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours, immediate intervention is required: 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
• Goal: Bring total 24-hour correction to no more than 8 mmol/L from starting point 1

Common Pitfalls to Avoid

1. Overly rapid correction exceeding 8 mmol/L in 24 hours leads to osmotic demyelination syndrome 1
2. Using fluid restriction in CSW worsens outcomes 1
3. Inadequate monitoring during active correction 1
4. Failing to recognize underlying cause 1
5. Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
6. Ignoring mild hyponatremia (130-135 mmol/L) as clinically insignificant—even mild hyponatremia increases fall risk (21% vs 5%) and mortality (60-fold increase with sodium <130 mmol/L) 1
7. Using normal saline in SIADH—this can worsen hyponatremia through dilution 1

Monitoring Protocol

• Severe symptoms: Check sodium every 2 hours during initial correction 1
• After symptom resolution: Check every 4 hours 1
• Stable patients: Daily monitoring until target reached 1
• Watch for osmotic demyelination syndrome signs (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1