What are the symptoms and treatment options for hyponatremia?

Symptoms and Treatment of Hyponatremia

Hyponatremia symptoms depend on both the absolute sodium level and the rate of development, with acute hyponatremia more likely to cause severe neurological symptoms due to cerebral edema, including delirium, impaired consciousness, ataxia, seizures, coma, and brain herniation. 1

Symptoms Based on Severity and Onset

Mild Hyponatremia (130-134 mmol/L)

• Nausea
• Weakness
• Headache
• Mild neurocognitive deficits
• Increased risk of falls and fractures 1, 2

Moderate Hyponatremia (125-129 mmol/L)

• Lack of concentration
• Forgetfulness
• Apathy
• Loss of balance
• Nausea and vomiting 3, 4

Severe Hyponatremia (<125 mmol/L)

• Delirium
• Confusion
• Impaired consciousness
• Ataxia
• Seizures
• Coma
• Brain herniation (rare but life-threatening) 1, 3

Treatment Algorithm Based on Volume Status and Symptom Severity

1. Severely Symptomatic Hyponatremia (Medical Emergency)

• For patients with somnolence, obtundation, coma, seizures, or cardiorespiratory distress:
  • Administer 3% hypertonic saline as 100-150 ml IV bolus or continuous infusion 1, 5
  • Target increase: 4-6 mmol/L within 1-2 hours
  • Do not exceed 8-10 mmol/L in 24 hours to avoid osmotic demyelination syndrome (ODS) 1
  • Monitor serum sodium every 2-4 hours initially 1

2. Treatment Based on Volume Status

Hypovolemic Hyponatremia

• Isotonic (0.9%) saline IV at initial rate of 60-100 mL/hour 1
• Address underlying cause (dehydration, gastrointestinal losses)

Euvolemic Hyponatremia

• Fluid restriction (<1-1.5 L/day) 1
• For SIADH:
  • Consider tolvaptan for patients not responding to fluid restriction 6, 5
  • Tolvaptan starting dose: 15 mg once daily, can be increased to 30 mg and then 60 mg 6
  • Alternative: oral urea (considered effective and safe) 5
  • Monitor for hypernatremia with tolvaptan therapy 6

Hypervolemic Hyponatremia

• Fluid restriction + diuretics 1
• Treat underlying condition (heart failure, cirrhosis, renal disease)
• Consider tolvaptan in heart failure patients with persistent hyponatremia 6, 4

Special Considerations and Pitfalls

High-Risk Populations

• Children (higher risk of symptomatic hyponatremia due to larger brain/skull ratio) 1
• Patients with severe malnutrition, alcoholism, advanced liver disease (higher risk for ODS) 1
• Cirrhotic patients (increased mortality with untreated hyponatremia) 1

Avoiding Complications

• Critical Pitfall: Overly rapid correction can lead to osmotic demyelination syndrome (ODS)
  • Presents 2-7 days after rapid correction
  • Initial symptoms: seizures or encephalopathy
  • Can progress to parkinsonism, quadriparesis, or death 1, 2
  • Correction rate should not exceed 8 mmol/L in 24 hours 1

Medication Considerations

• Avoid concomitant use of tolvaptan with strong CYP3A inhibitors (contraindicated) 6
• Monitor potassium levels when using tolvaptan with angiotensin receptor blockers, ACE inhibitors, or potassium-sparing diuretics 6
• Avoid grapefruit juice while taking tolvaptan 6

Monitoring Requirements

• Serum sodium every 2-4 hours in symptomatic patients 1
• Hemodynamic parameters (blood pressure, heart rate) 1
• Careful fluid input/output measurement 1
• Electrolyte balance monitoring, especially with pharmacologic interventions 1, 6

By addressing both the symptoms and underlying causes of hyponatremia while carefully monitoring correction rates, morbidity and mortality can be significantly reduced.