What are the treatment options for hyponatremia?

Treatment of Hyponatremia

Immediate Assessment and Classification

The treatment of hyponatremia depends critically on symptom severity, volume status, and chronicity—with severe symptomatic cases requiring immediate hypertonic saline to prevent life-threatening complications, while asymptomatic or mildly symptomatic cases are managed based on volume status with fluid restriction, isotonic saline, or treatment of underlying conditions. 1

Initial workup should include serum and urine osmolality, urine sodium, and assessment of extracellular fluid volume status to determine the underlying cause 1. Hyponatremia is defined as serum sodium <135 mEq/L, with severity classified as mild (130-134 mEq/L), moderate (125-129 mEq/L), and severe (<125 mEq/L) 2, 3.

Treatment Based on Symptom Severity

Severe Symptomatic Hyponatremia (Seizures, Coma, Altered Mental Status)

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

• Administer 100-150 mL bolus of 3% hypertonic saline over 10 minutes, which can be repeated up to three times at 10-minute intervals until symptoms improve 1, 5
• Transfer to ICU for close monitoring with serum sodium checks every 2 hours during initial correction 1, 4
• Total correction must not exceed 8 mmol/L in the first 24 hours to prevent osmotic demyelination syndrome 1, 4, 2
• After initial correction, monitor sodium every 4 hours and limit subsequent correction to <8 mmol/L per day 1

The rapid intermittent bolus administration is preferred over continuous infusion for symptomatic hyponatremia 5. However, overcorrection occurs in 4.5-28% of cases, with higher risk in severely symptomatic patients (38% vs 6% in moderate symptoms) 6.

Mild to Moderate Symptomatic or Asymptomatic Hyponatremia

Treatment is determined by volume status 1, 2:

Treatment Based on Volume Status

Hypovolemic Hyponatremia

For hypovolemic hyponatremia (urine sodium <30 mmol/L, signs of volume depletion), discontinue diuretics and administer isotonic (0.9%) saline for volume repletion 1, 3:

• Restore intravascular volume with normal saline or lactated Ringer's solution 1
• Once euvolemic, reassess and adjust treatment based on sodium response 1
• Correction rate should not exceed 8 mmol/L in 24 hours 1

Euvolemic Hyponatremia (SIADH)

For SIADH, fluid restriction to 1 L/day is the cornerstone of first-line treatment 1, 4, 3:

• Implement strict fluid restriction of 500-1000 mL/day initially, adjusted based on sodium response 1, 4, 5
• If no response to fluid restriction after 24-48 hours, add oral sodium chloride 100 mEq three times daily 1, 7
• Adequate solute intake with high protein diet to augment solute load 7, 5

Second-line pharmacological options for SIADH refractory to fluid restriction 1, 5:

• Urea is considered very effective and safe, though has poor palatability 2, 5
• Vaptans (tolvaptan 15 mg once daily, titrated based on response) can increase sodium levels but carry risk of overly rapid correction and increased thirst 1, 2, 5
• Demeclocycline or lithium are less commonly used due to side effects 1, 4

Almost half of SIADH patients do not respond to fluid restriction as first-line therapy, necessitating second-line treatment 5.

Hypervolemic Hyponatremia (Heart Failure, Cirrhosis)

For hypervolemic hyponatremia, implement fluid restriction to 1-1.5 L/day for sodium <125 mEq/L and treat the underlying condition 1, 3:

• Fluid restriction to 1000-1500 mL/day is the primary intervention 1, 3
• Sodium restriction (not fluid restriction) is what drives weight loss, as fluid passively follows sodium 1
• Temporarily discontinue diuretics if sodium <125 mEq/L 1
• In cirrhotic patients, consider albumin infusion (6-8 g per liter of ascites drained) alongside fluid restriction 1, 3
• Avoid hypertonic saline unless life-threatening symptoms are present, as it may worsen edema and ascites 1
• Vaptans may be considered for persistent severe hyponatremia despite fluid restriction and optimization of guideline-directed therapy, but use with extreme caution in cirrhosis due to increased risk of gastrointestinal bleeding 1

Critical Correction Rate Guidelines

The maximum correction rate is 8 mmol/L in 24 hours for most patients to prevent osmotic demyelination syndrome 1, 2, 5:

• For chronic hyponatremia (>48 hours), limit correction to 0.5 mmol/L per hour or 8 mmol/L per 24 hours 1, 8
• High-risk patients (advanced liver disease, alcoholism, malnutrition, prior encephalopathy) require even more cautious correction of 4-6 mmol/L per day 1, 2
• Acute hyponatremia (<48 hours) can be corrected more rapidly without risk of osmotic demyelination 1
• After reaching 125-130 mEq/L, halt aggressive correction and proceed more gradually 8

Special Considerations: Cerebral Salt Wasting (CSW)

In neurosurgical patients, distinguish CSW from SIADH, as CSW requires volume and sodium replacement, NOT fluid restriction 1, 4:

• CSW is characterized by true hypovolemia with high urine sodium (>20 mmol/L) despite volume depletion 1
• Treatment focuses on aggressive volume replacement with isotonic or hypertonic saline 1
• For severe symptoms, administer 3% hypertonic saline plus fludrocortisone in ICU setting 1
• Fluid restriction in CSW worsens outcomes and should be avoided 1, 4
• In subarachnoid hemorrhage patients at risk for vasospasm, avoid fluid restriction and consider fludrocortisone or hydrocortisone 1

Management of Overcorrection

If sodium correction exceeds 8 mmol/L in 24 hours, immediately intervene to prevent osmotic demyelination syndrome 1:

• Discontinue current fluids and switch to D5W (5% dextrose in water) 1
• Consider administering desmopressin to slow or reverse the rapid rise 1
• Target relowering to bring total 24-hour correction to no more than 8 mmol/L from baseline 1
• Monitor for signs of osmotic demyelination syndrome (dysarthria, dysphagia, oculomotor dysfunction, quadriparesis) typically occurring 2-7 days after rapid correction 1

Monitoring Requirements

• Severe symptoms: Check sodium every 2 hours during initial correction 1, 4
• After symptom resolution: Check sodium every 4 hours 1
• Stable patients: Daily sodium monitoring until stable 1
• Monitor diuresis closely, as it correlates with sodium overcorrection 6
• Calculate sodium deficit using: Desired increase in Na (mEq/L) × (0.5 × ideal body weight in kg) 1, 7

Common Pitfalls to Avoid

• Overly rapid correction exceeding 8 mmol/L in 24 hours leading to osmotic demyelination syndrome 1, 2
• 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, 4
• Using hypertonic saline in hypervolemic hyponatremia without life-threatening symptoms 1
• Ignoring mild hyponatremia (130-135 mEq/L) as clinically insignificant—even mild hyponatremia increases fall risk (21% vs 5%), fracture risk, and mortality (60-fold increase when <130 mEq/L) 1, 2