How to manage hyponatremia (low sodium levels)?

Management of Hyponatremia

The treatment of hyponatremia should be tailored to the specific type (hypovolemic, euvolemic, or hypervolemic), severity of symptoms, and underlying cause, with fluid restriction of 1-1.5 L/day reserved for patients with severe hyponatremia (serum sodium <125 mmol/L) who are clinically hypervolemic. 1

Classification and Assessment

Hyponatremia is defined as serum sodium concentration <135 mmol/L, with severity categorized as:

• Mild: 130-134 mmol/L
• Moderate: 125-129 mmol/L
• Severe: <125 mmol/L 2

Initial evaluation should determine:

1. Volume status: Hypovolemic, euvolemic, or hypervolemic
2. Symptom severity: Mild (nausea, weakness, headache) vs. severe (delirium, seizures, coma)
3. Rate of development: Acute (<48 hours) vs. chronic (>48 hours)

Treatment Algorithm Based on Type and Severity

1. Hypovolemic Hyponatremia

• Cause: Excessive diuretic use, dehydration, third-space losses
• Treatment:
  • Plasma volume expansion with normal saline 1
  • Correction of the underlying cause (e.g., discontinuation of diuretics) 1
  • In severe cases, hypertonic saline (3%) may be considered 1

2. Euvolemic Hyponatremia (SIADH)

• Cause: Syndrome of inappropriate antidiuretic hormone secretion
• Treatment:
  • Fluid restriction (1-1.5 L/day) if serum sodium <125 mmol/L 1
  • Consider urea or vaptans (tolvaptan) as second-line therapy 3
  • Treat underlying cause if identified

3. Hypervolemic Hyponatremia

• Cause: Heart failure, cirrhosis, nephrotic syndrome
• Treatment:
  • Sodium restriction (5-6.5 g/day or 87-113 mmol/day) 1
  • Diuretic therapy: Spironolactone (starting 100 mg, up to 400 mg) alone or in combination with furosemide (starting 40 mg, up to 160 mg) 1
  • Fluid restriction (1-1.5 L/day) if serum sodium <125 mmol/L 1

Management of Severe Symptomatic Hyponatremia

For patients with severe symptoms (seizures, coma, cardiorespiratory distress):

1. Administer 3% hypertonic saline:

   • Initial correction: 5 mmol/L in the first hour 1
   • Maximum correction: 8 mmol/L in 24 hours 1
   • Goal: Attenuate clinical symptoms while avoiding osmotic demyelination 1

2. Monitor serum sodium frequently during correction

3. Avoid overcorrection: Risk of central pontine myelinolysis increases with correction >8 mmol/L per day 1

Special Considerations in Cirrhosis

In patients with cirrhosis and hyponatremia:

• Discontinue diuretics if hypovolemic hyponatremia develops 1
• Albumin infusion (1.5 g/kg within 6 hours, followed by 1 g/kg on day 3) may improve serum sodium in patients with spontaneous bacterial peritonitis and elevated creatinine 1
• Consider TIPSS (transjugular intrahepatic portosystemic shunt) in refractory cases 1

Role of Vaptans

Vaptans (V2-receptor antagonists) may be considered in selected cases:

• Mechanism: Enhance solute-free water excretion by blocking vasopressin action 1
• Efficacy: Improve serum sodium in 45-82% of cirrhotic patients with hyponatremia 1
• FDA-approved options: Tolvaptan for euvolemic and hypervolemic hyponatremia 4
• Caution: Safety established only for short-term use (1 week to 1 month) 1

Common Pitfalls to Avoid

1. Overly rapid correction: Do not exceed 8 mmol/L per day to prevent central pontine myelinolysis 1

2. Indiscriminate use of hypertonic saline: Reserve for severely symptomatic patients; can worsen ascites and edema in hypervolemic states 1

3. Inadequate monitoring: Frequent sodium measurements are essential during active correction

4. Failure to identify and treat the underlying cause: Essential for long-term management

5. Relying solely on fluid restriction: Often insufficient as monotherapy, especially in hypervolemic states 1

By following this structured approach based on volume status and symptom severity, clinicians can effectively manage hyponatremia while minimizing complications and improving outcomes.