Treatment of Hypertonic Dehydration in Pediatrics
For hypertonic (hypernatremic) dehydration in children, use slow rehydration with isotonic fluids (0.9% NaCl or 0.18% saline in 4.3% dextrose) over 48 hours, ensuring the serum osmolality decreases no faster than 3 mOsm/kg/H2O per hour to prevent cerebral edema. 1, 2
Initial Assessment and Recognition
Hypertonic dehydration (serum sodium >145-150 mEq/L) presents differently than isotonic dehydration and requires specific recognition:
- Key clinical features: Doughy skin texture, irritability or lethargy, high-pitched cry, and paradoxically better-preserved intravascular volume compared to isotonic dehydration 3, 4
- Severity grading: Mild (3-5% deficit), moderate (6-9% deficit), or severe (≥10% deficit) based on clinical signs including skin turgor, mucous membrane dryness, perfusion status, and mental status 5, 6
- Critical distinction: Unlike isotonic dehydration, rapid correction of hypernatremia causes dangerous osmotic shifts leading to cerebral edema and seizures 1, 3
Fluid Selection and Rate: The Critical Difference
The fundamental principle is SLOW correction with specific fluid choices:
For Mild to Moderate Hypernatremic Dehydration:
- Use 0.18% saline (1/5 normal saline) in 4.3% dextrose at 100 mL/kg estimated rehydrated weight per 24 hours 1
- Alternative: 0.45% saline (1/2 normal saline) given slowly, though 0.18% saline is preferred for hypernatremia 1
- Add potassium (20-40 mEq/L as 2/3 KCl and 1/3 KPO4) once urine output is established 5, 2
For Severe Hypernatremic Dehydration with Shock:
- Initial resuscitation: 10-20 mL/kg boluses of 0.9% NaCl to restore perfusion 5, 2
- After stabilization: Switch immediately to hypotonic fluid (0.18-0.45% saline) for gradual correction 1, 2
- Do NOT continue isotonic fluids beyond initial resuscitation as this worsens hypernatremia 1
Rate of Correction: The Most Critical Parameter
The rate of sodium decrease must be controlled to prevent cerebral edema:
- Maximum safe rate: Decrease serum osmolality by no more than 3 mOsm/kg/H2O per hour 5
- Practical target: Reduce serum sodium by 0.5 mEq/L per hour or 10-12 mEq/L per 24 hours 3, 2
- Rehydration timeframe: Plan for 48 hours (or up to 72 hours for severe cases) to achieve complete rehydration 1, 7
- Calculate corrected sodium: For each 100 mg/dL glucose above 100 mg/dL, add 1.6 mEq/L to measured sodium 5
Monitoring Requirements
Frequent reassessment is mandatory to prevent complications:
- Clinical monitoring: Mental status, skin turgor, perfusion, urine output every 2-4 hours 5, 4
- Laboratory monitoring: Serum sodium, glucose, and osmolality every 4-6 hours initially 5, 2
- Watch for complications: Seizures, altered consciousness, or rapid changes in neurological status indicating cerebral edema 1, 3
Special Considerations and Pitfalls
Common Errors to Avoid:
- Never use standard ORS protocols designed for isotonic dehydration—these contain 50-90 mEq/L sodium and will not correct hypernatremia adequately 5, 6
- Never correct rapidly: This is the most dangerous error, causing osmotic demyelination or cerebral edema 1, 3
- Never use hypotonic maintenance fluids (like 0.2% or 0.45% saline) for routine maintenance in other conditions, but these ARE appropriate for hypernatremic dehydration correction 1, 3
When Peritoneal Dialysis is Indicated:
- Consider in the most severe cases with extreme hypernatremia (Na >180 mEq/L), renal failure, or inability to achieve controlled correction with IV fluids 7
Ongoing Loss Replacement:
- Replace continuing diarrheal losses with 10 mL/kg per stool using isotonic fluids (0.9% NaCl), NOT the hypotonic correction fluid 5
- This prevents worsening hypernatremia from ongoing free water losses 2
Transition to Maintenance
Once serum sodium normalizes (typically 48 hours):