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Pediatric Hypotonic Dehydration

Aka: Pediatric Hypotonic Dehydration, Hypotonic Dehydration Management in Children
  1. See Also
    1. Pediatric Dehydration Management
    2. Hyponatremia
  2. Definitions
    1. Pediatric Hypotonic Dehydration
      1. Pediatric Dehydration AND Serum Sodium < 130
      2. Occurs when gastrointestinal losses are replaced with water (or other hypotonic solutions)
  3. Protocol: Example Case
    1. Weight: 35 kg Child
    2. Dehydration: 10%
    3. Serum Sodium: 120
  4. Protocol: Stabilization with Bolus Fluids (Phase I)
    1. See Pediatric Dehydration Management
    2. Give 20 ml/kg Normal Saline or Lactated Ringers over 10-15 minutes
    3. May repeat bolus until circulation stable
      1. May require up to 60 ml/kg within the first 1-2 hours
  5. Protocol: Calculate Replacement and Replace Phase 1 Fluids
    1. Approach as per Pediatric Dehydration Management
    2. Deficit: 3500 - 700 ml (Replaced Phase 1)
    3. Maintenance: 4*10+2*10+1*15= 75 ml/h
      1. See Maintenance Fluid Requirements in Children
    4. Replacement of 2800 ml over 24 hours
      1. First 8 hours
        1. Total: 1400/8 ml/h + (maintenance 75 ml/h) for 8 hours
        2. Hourly: 250 ml/hour for 8 hours (2 Liters over 8h)
          1. NS delivers (154 meq/1000 ml)(250 ml/h) = 39 meq/h Sodium
      2. Next 16 hours
        1. Total: 1400/16 ml/h + (maintenance 75 cc/h) for 16 hours
        2. Hourly: 163 ml/hour for 16 hours (2.6L over 16h)
          1. NS delivers (154 meq/1000 ml)(163 ml/h) = 25 meq/h Sodium
    5. Replacement of 2800 ml over 48 hours
      1. First 16 hours
        1. Total: 1400/16 ml/h + (maintenance 75 ml/h) for 16 hours
        2. Hourly: 163 ml/hour for 16 hours (2.6 Liters over 16h)
          1. NS delivers (154 meq/1000 ml)(163 ml/h) = 25 meq/h Sodium
      2. Next 32 hours
        1. Total: 1400/32 ml/h + (maintenance 75 cc/h) for 32 hours
        2. Hourly: 118 ml/hour for 32 hours (3.78 L over 32h)
          1. NS delivers (154 meq/1000 ml)(118 ml/h) =18 meq/h Sodium
  6. Protocol: Calculate Sodium Deficit and Sodium Requirement
    1. Calculate Deficit
      1. Formula: 0.6 x (weight kg) x (135 - Serum Sodium)
        1. Where 0.6 is volume of distribution (per kg)
        2. Where 135 is the desired Serum Sodium
      2. Example: (0.6 x 35 kilograms) x (135-120) = 315 meq
    2. Add Maintenance
      1. Formula: 3 meq/kg/day x (weight kg)
      2. Example: 3 meq/kg/24h x 35 kg = 105 meq Sodium/24 hours
    3. Subtract Replacement given Phase 1
      1. Phase 1 Fluid bolus
        1. NS: 1000 ml contains 154 meq Sodium
        2. Example: 700 cc contains 108 meq Sodium
      2. Remaining Sodium Required: 315 - 108 = 207 meq
  7. Protocol: Choose Appropriate solution to replace Sodium deficit
    1. Available solutions
      1. Normal Saline contains 154 meq/L Sodium (typical replacement)
    2. Example: Replacement over 24 hours
      1. First 8 hours: Replace half Sodium deficit (104 meq)
        1. Maintenance Sodium requirement in 8 hours = 105*(1/3) = 35 meq
        2. Total Sodium requirement in 8 hours = 104 + 35 = 139 meq or 17 meq/h
        3. Sodium Requirements: NS at 118 ml/hour delivers 18 meq/h Sodium
        4. Fluid Requirements: NS at 250 ml/hour delivers 39 meq/h Sodium (calculated above)
      2. Next 16 hours: Replace half Sodium deficit (104 meq)
        1. Maintenance Sodium requirement in 16 hours = 105*(2/3) = 70 meq
        2. Total Sodium requirement in 16 hours = 104 + 70 = 174 meq or 11 meq/h
        3. Sodium Requirements: NS at 71 ml/hour delivers 11 meq/h Sodium
        4. Fluid Requirements: NS at 163 ml/hour delivers 25 meq/h Sodium (calculated above)
    3. Example: Replacement over 48 hours
      1. First 16 hours: Replace half Sodium deficit (104 meq)
        1. Maintenance Sodium requirement in 16 hours = 105*(2/3) = 70 meq
        2. Total Sodium requirement in 16 hours = 104 + 70 = 174 meq or 17 meq/h
        3. Sodium Requirements: NS at 118 ml/hour delivers 18 meq/h Sodium
        4. Fluid Requirements: NS at 163 ml/hour delivers 25 meq/h Sodium (calculated above)
      2. Next 32 hours: Replace half Sodium deficit (104 meq)
        1. Maintenance Sodium requirement in 32 hours = 104*(4/3) = 139 meq
        2. Total Sodium requirement in 32 hours = 104 + 139 = 243 meq or 8 meq/h
        3. Sodium Requirements: NS at 52 ml/hour delivers 8 meq/h Sodium
        4. Fluid Requirements: NS at 118 ml/hour delivers 18 meq/h Sodium (calculated above)
  8. Protocol: Example Summary - 35 kg Child with hypotonic dehydration
    1. Given the severe Hyponatremia on presentation, replacement over 48 hours appears safer
      1. When instead, replaced over 24 hours, initial 250 ml/h rate would supply double the Sodium requirement
      2. Delivering Fluid Replacement over 48 hours allows for slower, safer raising of Sodium
    2. Replacement over 48 hours
      1. First 16 hours: D5 NS with 20 KCl at 163 ml/hour delivers 25 meq/h Sodium
      2. Next 32 hours: D5 NS with 20 KCl at 118 ml/hour delivers 18 meq/h Sodium
  9. Labs: Monitoring
    1. Monitor Serum Sodium every 2-4 hours
    2. Raise Serum Sodium <= 8-12 mEq/L/24 hours (or <0.5 mEq/hour, <2 mEq in 4 hours)
  10. Management: Special Circumstance - Hyponatremic Seizure
    1. Background
      1. Serum Sodium raised 5 meq/L with 6 ml/kg of 3% NaCl (513 meq/L)
    2. Protocol
      1. Give 3% NaCl at 3 to 5 ml/kg/hour until Seizure stops
  11. Resources
    1. Vega and Bhimji (2017) Pediatric Dehydration in Stat Pearls
      1. https://www.ncbi.nlm.nih.gov/books/NBK436022/
  12. References
    1. Walton (2020) Crit Dec Emerg Med 34(6): 3-9
    2. Canavan (2009) Am Fam Physician 80(7):692-6 [PubMed]

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