How to manage a patient with acute on chronic hyponatremia receiving Normal Saline (NS) with 20 units of Kayexalate (sodium polystyrene sulfonate)?

Management of Acute on Chronic Hyponatremia with Sodium Level of 107 mEq/L

For a patient with severe acute on chronic hyponatremia (Na 107 mEq/L) receiving normal saline with Kayexalate, the treatment should focus on careful correction of sodium at a rate not exceeding 8-10 mEq/L in the first 24 hours to prevent osmotic demyelination syndrome. 1

Initial Assessment and Management

1. Determine volume status and severity:

   • Sodium level of 107 mEq/L indicates severe hyponatremia 1, 2
   • Assess for neurological symptoms (altered mental status, seizures, coma)
   • Evaluate volume status (hypovolemic, euvolemic, or hypervolemic)

2. For symptomatic severe hyponatremia:

   • If severe neurological symptoms present (seizures, coma):
     • Administer 3% hypertonic saline as bolus to increase sodium by 4-6 mEq/L within 1-2 hours 1
     • Initial bolus: 100-150 mL of 3% saline over 10-20 minutes
     • Can repeat bolus if symptoms persist

3. For less severe symptoms or asymptomatic:

   • Normal saline (0.9%) is appropriate for hypovolemic hyponatremia 1, 3
   • For euvolemic or hypervolemic hyponatremia, consider fluid restriction (<1 L/day) 1

Correction Rate and Monitoring

• Target correction rate:

  • Do not exceed 8-10 mEq/L in first 24 hours 1, 4
  • Do not exceed 18 mEq/L in 48 hours 1
  • For high-risk patients (alcoholism, malnutrition, liver disease, hypokalemia), limit to 4-6 mEq/L/day 1

• Monitoring:

  • Check serum sodium every 2-4 hours during active correction 1
  • Monitor neurological status continuously for signs of deterioration
  • Target correction rate: 0.5-1 mEq/L/hour initially 1, 5

Special Considerations with Kayexalate (Sodium Polystyrene Sulfonate)

• Kayexalate contains significant sodium (100 mg sodium per gram of resin) which can contribute to sodium correction 1
• When administering Kayexalate (20 units):
  • Account for sodium content in correction calculations
  • Monitor for hyperkalemia reversal which may affect neurological status
  • Consider central line placement for administration of potassium solutions 1

Risk Management

• Watch for signs of osmotic demyelination syndrome:

  • Dysarthria, dysphagia, altered mental status, quadriparesis 1, 4
  • If neurological deterioration occurs during correction, consider desmopressin to slow correction 1

• If correction is too rapid:

  • Stop current therapy
  • Consider administration of hypotonic fluids and/or desmopressin to re-lower sodium 1, 4

Algorithm for Ongoing Management

1. If hypovolemic:

   • Continue normal saline at calculated rate to achieve target correction
   • Replace potassium as needed (with caution given Kayexalate use)

2. If euvolemic:

   • Consider switching from normal saline to fluid restriction
   • Evaluate for SIADH and treat underlying cause

3. If hypervolemic:

   • Implement fluid restriction (<1 L/day)
   • Consider loop diuretics with careful monitoring 6, 1
   • Address underlying cause (heart failure, cirrhosis)

Pitfalls to Avoid

• Overly rapid correction leading to osmotic demyelination syndrome 1, 4
• Inadequate monitoring of serum sodium during correction
• Failure to account for sodium content in Kayexalate when calculating correction rates
• Ignoring potassium levels, which can affect neurological status and treatment response 1
• Continuing normal saline in hypervolemic patients, which may worsen volume overload 6, 1

Remember that chronic hyponatremia (>48 hours) requires more cautious correction than acute hyponatremia to prevent neurological complications 4, 5. The presence of Kayexalate in the treatment regimen suggests possible concurrent hyperkalemia, which should be addressed simultaneously but with careful attention to the sodium correction rate.