What are the steps for treating hyponatremia (low sodium levels in the blood)?

Hyponatremia Treatment: Step-by-Step Approach

The treatment of hyponatremia must be tailored to the underlying cause, volume status, symptom severity, and rate of development, with careful monitoring to prevent overcorrection and osmotic demyelination syndrome. 1

Step 1: Assess Severity and Symptoms

• Classify hyponatremia by severity:

  • Mild: 126-135 mEq/L
  • Moderate: 120-125 mEq/L
  • Severe: <120 mEq/L 1

• Evaluate symptoms:

  • Severe symptoms: Mental status changes, seizures, coma
  • Mild symptoms: Nausea, vomiting, headache, weakness
  • Asymptomatic 2, 3

Step 2: Determine Volume Status and Cause

• Assess volume status using clinical examination and laboratory tests:

Volume Status	Urine Osmolality	Urine Sodium	Suggested Diagnosis
Hypovolemic	Variable	<20 mEq/L	Volume depletion
Euvolemic	>500 mOsm/kg	>20-40 mEq/L	SIADH
Hypervolemic	Elevated	<20 mEq/L	Heart failure, cirrhosis

• Central venous pressure (CVP) can help distinguish SIADH from cerebral salt wasting (CSW):
  • SIADH: CVP 6-10 cm H₂O (normovolemic)
  • CSW: CVP <6 cm H₂O (hypovolemic) 2

Step 3: Treatment Based on Symptoms and Volume Status

For Severe Symptomatic Hyponatremia (Mental status changes, seizures)

1. Administer 3% hypertonic saline:

   • Give as 100-150 mL bolus or continuous infusion 4
   • Target correction: 4-6 mEq/L within 1-2 hours or until severe symptoms improve 2, 1
   • Maximum correction: 8 mEq/L in first 24 hours 2
   • Formula for sodium deficit: Desired increase in Na (mEq/L) × (0.5 × ideal body weight) 2

2. Monitor serum sodium every 2 hours during active correction 1

3. Transfer to ICU for close monitoring 2

4. Once severe symptoms resolve, transition to treatment for mild symptoms or asymptomatic protocol 2

For Hypovolemic Hyponatremia

1. Discontinue diuretics/laxatives if applicable 1

2. Administer isotonic (0.9%) saline at 50 mL/kg/day plus salt supplementation (12 g/day) 2

3. For CSW patients: Consider fludrocortisone (mineralocorticoid) to enhance sodium reabsorption 2

For Euvolemic Hyponatremia (SIADH)

1. Fluid restriction (500-1000 mL/day) as first-line therapy 2, 1

2. If no response to fluid restriction:

   • Add oral sodium chloride 100 mEq TID
   • Consider high protein diet 2

3. For resistant cases:

   • Consider urea (40 g in 100-150 mL normal saline every 8 hours) 2
   • Consider tolvaptan (vasopressin receptor antagonist) starting at 15 mg once daily for short-term use (≤30 days) 1, 5

For Hypervolemic Hyponatremia

1. Fluid restriction to 1000 mL/day 1

2. Treat underlying condition (heart failure, cirrhosis) 1, 6

3. For severe cases: Consider albumin infusion with fluid restriction 1

Step 4: Monitor Correction Rate

• Maximum safe correction rates:

  • General population: 10-12 mEq/L in 24 hours 1, 7
  • High-risk patients (alcoholism, malnutrition, liver disease): 4-6 mEq/L in 24 hours 1

• Monitoring frequency:

  • Every 2-4 hours initially during active correction
  • Every 4-6 hours during ongoing treatment
  • Daily once stabilized 1

• If correction is occurring too rapidly:

  • Administer hypotonic fluids
  • Consider desmopressin to prevent further water excretion 1

Important Precautions

• Avoid fluid restriction in CSW patients as it can increase risk of cerebral infarction (21/26 fluid-restricted patients developed cerebral infarction in one study) 2

• Avoid rapid correction of chronic hyponatremia to prevent osmotic demyelination syndrome, which can cause parkinsonism, quadriparesis, or death 3

• For chronic hyponatremia (>48 hours), use a slower correction rate and close monitoring 8

• For SAH patients, maintain sodium levels >135 mEq/L to prevent increased risk of cerebral ischemia 2

By following this algorithmic approach to hyponatremia treatment, clinicians can effectively manage this common electrolyte disorder while minimizing the risk of complications from both the condition itself and its treatment.