Inpatient Treatment Approach for Hyponatremia
The treatment of hyponatremia in hospitalized patients must be tailored to the underlying etiology, severity, chronicity, and volume status, with careful attention to the rate of correction to prevent osmotic demyelination syndrome. 1
Initial Assessment and Classification
1. Determine Volume Status
- Hypovolemic hyponatremia: Signs of volume depletion (tachycardia, orthostatic hypotension, dry mucous membranes)
- Euvolemic hyponatremia: No signs of volume depletion or overload
- Hypervolemic hyponatremia: Signs of volume overload (edema, ascites, elevated JVP)
2. Assess Severity
- Mild: 126-135 mEq/L
- Moderate: 120-125 mEq/L
- Severe: <120 mEq/L 1
3. Evaluate Chronicity
- Acute: Developed within 48 hours
- Chronic: Developed over >48 hours 1
4. Check for Symptoms
- Mild symptoms: Nausea, muscle cramps, gait instability, headache, dizziness
- Severe symptoms: Confusion, seizures, coma, cardiorespiratory distress 1, 2
Treatment Algorithm Based on Classification
1. Severely Symptomatic Hyponatremia (Medical Emergency)
- Administer hypertonic (3%) saline to increase serum sodium by 4-6 mEq/L within 1-2 hours until symptoms resolve 2
- Correction limits:
- Monitor serum sodium every 2-4 hours to avoid overcorrection
2. Hypovolemic Hyponatremia
- Discontinue diuretics and/or laxatives if they are contributing factors 1
- Provide fluid resuscitation with:
- 5% IV albumin (preferred in cirrhosis) or
- Crystalloid solution (preferentially lactated Ringer's) 1
- Monitor response and adjust therapy based on serum sodium levels
3. Euvolemic Hyponatremia
- Identify and treat specific underlying cause (SIADH, hypothyroidism, adrenal insufficiency, medications) 1
- For SIADH:
4. Hypervolemic Hyponatremia
- Fluid restriction to 1,000 mL/day for moderate hyponatremia (120-125 mEq/L) 1
- More severe fluid restriction plus albumin infusion for severe hyponatremia (<120 mEq/L) 1
- Reduce or discontinue diuretics and laxatives if contributing to hyponatremia 1
- Consider hyperoncotic albumin administration 1
- For heart failure patients with persistent severe hyponatremia despite water restriction and GDMT:
- Consider short-term vasopressin antagonists to improve serum sodium 1
Special Considerations
Cirrhosis with Hyponatremia
- Mild hyponatremia (126-135 mEq/L): Monitor and restrict water intake 1
- Moderate hyponatremia (120-125 mEq/L): Fluid restriction to 1,000 mL/day 1
- Severe hyponatremia (<120 mEq/L): More severe fluid restriction plus albumin infusion 1
- Avoid vaptans for long-term use due to safety concerns and higher mortality rates 1
Vasopressin Antagonists (Vaptans)
- Consider for short-term use only (up to 30 days) 4
- Initiate in hospital setting to evaluate therapeutic response and avoid too rapid correction 4
- Starting dose: Tolvaptan 15 mg once daily, may increase to 30 mg after 24 hours, maximum 60 mg daily 4
- Avoid fluid restriction during first 24 hours of vaptan therapy 4
- Monitor serum sodium frequently during initiation and titration 4
Critical Pitfalls to Avoid
1. Overly Rapid Correction
- Risk of osmotic demyelination syndrome (ODS) with rapid correction of chronic hyponatremia 1, 2
- Symptoms of ODS: Dysarthria, mutism, dysphagia, parkinsonism, quadriparesis, seizures, coma 1
- Higher risk patients: Advanced liver disease, alcoholism, severe hyponatremia, malnutrition, hypokalemia, hypophosphatemia 1
2. Inadequate Monitoring
- Frequent monitoring is essential, especially during correction of severe hyponatremia
- Relowering with electrolyte-free water or desmopressin may be considered if overcorrection occurs 1
3. Inappropriate Treatment Selection
- Hypertonic saline should be reserved for severely symptomatic patients 1, 2
- Vaptans should be used cautiously and only for short-term treatment 1, 4
By following this structured approach to inpatient hyponatremia management, clinicians can effectively treat this common electrolyte disorder while minimizing the risks of complications associated with both the condition itself and its treatment.