How is hyponatremia treated?

Treatment of Hyponatremia Based on Volume Status and Severity

The treatment of hyponatremia should be guided by the patient's volume status (hypovolemic, euvolemic, or hypervolemic) and symptom severity, with correction rates carefully monitored to prevent neurological complications. 1

Initial Assessment

Volume Status Determination

• Hypovolemic: Orthostatic hypotension, dry mucous membranes, urine Na <20 mEq/L
• Euvolemic: Normal vital signs, no edema, urine Na >20-40 mEq/L
• Hypervolemic: Edema, ascites, elevated JVP, urine Na <20 mEq/L 1

Symptom Severity Classification

• Severe symptoms: Mental status changes, seizures, coma
• Mild symptoms: Nausea, vomiting, headache, weakness
• Asymptomatic: No clinical manifestations 2

Treatment Algorithm by Volume Status

1. Hypovolemic Hyponatremia

• Primary treatment: Isotonic (0.9%) saline to restore volume 1
• Monitoring: Check serum sodium every 2-4 hours initially during correction 1
• Goal: Address underlying cause (e.g., GI losses, diuretics) 3

2. Euvolemic Hyponatremia (e.g., SIADH)

• First-line: Fluid restriction (1-1.5 L/day) 1
• If severe symptoms present:
  • 3% hypertonic saline (100-150 mL bolus or continuous infusion) 4
  • Correct 6 mEq/L in first 6 hours or until severe symptoms resolve 2
• Second-line options (if fluid restriction fails):
  • Tolvaptan starting at 15 mg once daily (for short-term ≤30 days) 5
  • Oral urea 4
  • Salt tablets 6

3. Hypervolemic Hyponatremia (e.g., heart failure, cirrhosis)

• Primary approach: Fluid restriction to 1,000 mL/day 1
• Pharmacologic options:
  • Loop diuretics 7
  • Albumin infusion for severe cases 1
  • Tolvaptan (with careful monitoring) 5

Correction Rate Guidelines

• Severe symptomatic hyponatremia: Increase Na by 1-2 mEq/L per hour until symptoms abate 7
• Maximum correction limits:
  • 8 mEq/L in 24 hours 2
  • 18 mEq/L in 48 hours 7
• High-risk patients: Limit correction to 4-6 mEq/L per day 1

Special Considerations

Cerebral Salt Wasting (CSW)

• Treatment: Aggressive volume resuscitation with sodium and fluid replacement 1
• Pharmacologic option: Fludrocortisone 0.1-0.2 mg three times daily 1
• Monitoring: Central venous pressure (CVP <6 cm H₂O suggests CSW) 1

Subarachnoid Hemorrhage Patients

• Treatment threshold: Even for serum Na 131-135 mEq/L 2
• Approach: More aggressive volume resuscitation to prevent vasospasm 1

Complications to Monitor

• Osmotic demyelination syndrome: Risk increases with overly rapid correction (>12 mEq/L per 24 hours) 7
• Symptoms of overcorrection: Parkinsonism, quadriparesis 3
• Prevention: Frequent monitoring (every 2-4 hours initially) and adjustment of treatment 1

Pitfalls to Avoid

• Misdiagnosis of volume status: Incorrectly treating SIADH with saline or CSW with fluid restriction can worsen hyponatremia 2
• Inadequate monitoring: Failure to check sodium levels frequently during active correction 1
• Excessive correction: Particularly dangerous in chronic hyponatremia (>48 hours duration) 8
• Undertreating severe symptoms: Delaying hypertonic saline in patients with seizures or altered mental status 3

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