What is the treatment for hypernatremia in a child with vomiting and poor appetite?

Treatment of Hypernatremia in a 7-Year-Old with Vomiting and Poor Appetite

For a 7-year-old child with hypernatremia and vomiting, use oral rehydration solution (ORS) if the child can tolerate oral intake, or 5% dextrose in water intravenously if oral rehydration fails, while avoiding normal saline which will worsen hypernatremia. 1, 2

Initial Assessment and Fluid Selection

The cornerstone of treatment is determining the severity of dehydration and selecting appropriate hypotonic fluids:

• Assess dehydration severity by evaluating pulse, perfusion, mental status, and weight loss, noting that signs of dehydration may be masked in hypernatremic children 1
• For mild to moderate dehydration with tolerable vomiting: Administer ORS at 50-100 mL/kg over 3-4 hours, as low-osmolarity ORS is safe in the presence of hypernatremia 1
• If vomiting prevents oral intake: Consider nasogastric ORS administration before resorting to intravenous therapy 1
• For severe dehydration, persistent vomiting, or altered mental status: Use intravenous 5% dextrose in water as the primary rehydration fluid 1, 2

Critical Fluid Selection Principle

Never use normal saline (0.9% NaCl) as the primary rehydration fluid in hypernatremia:

• Normal saline has a tonicity of 300 mOsm/kg, which exceeds typical urine osmolality in dehydrated children (100 mOsm/kg) by 3-fold 1
• This means approximately 3 liters of urine are needed to excrete the osmotic load from 1 liter of isotonic fluid, risking worsening hypernatremia 1, 2
• 5% dextrose delivers no renal osmotic load, making it the appropriate choice for hypernatremic correction 1, 2

Rate of Correction

Correct hypernatremia slowly to prevent cerebral edema and seizures:

• Target reduction rate: 10-15 mmol/L per 24 hours maximum 1, 2
• Optimal rate: Approximately 0.5 mmol/L per hour 2
• Calculate initial IV fluid rate (if needed): For a 7-year-old (~20-25 kg), use 100 mL/kg/24h for first 10 kg + 50 mL/kg/24h for next 10-15 kg = approximately 1500-1750 mL/24h as starting maintenance 1, 2
• Rapid correction of chronic hypernatremia (>48 hours) can cause cerebral edema, seizures, and neurological injury 1, 3

Ongoing Replacement During Treatment

Replace ongoing losses from continued vomiting:

• For children >10 kg body weight: Give 120-240 mL ORS for each vomiting episode, up to ~1 L/day 1
• If unable to drink and requiring IV therapy: Use 5% dextrose 0.25 normal saline with 20 mEq/L potassium chloride intravenously for maintenance after initial correction 1
• Continue replacement as long as vomiting persists 1

Monitoring Requirements

Close monitoring is essential to avoid complications:

• Check serum sodium every 2-4 hours initially during active correction, especially if using IV fluids 1, 2
• Monitor for signs of cerebral edema: altered mental status, seizures, worsening neurological status 2, 3
• Track daily weight and input/output 1, 2
• Target normalization within 48-72 hours 2

Additional Management Considerations

Address the underlying cause and nutritional needs:

• Investigate and treat the cause of vomiting and poor appetite 3
• Ensure adequate caloric intake alongside rehydration, especially important in children with poor appetite 2
• Once rehydration is complete, resume age-appropriate normal diet offered every 3-4 hours 1

Common Pitfalls to Avoid

Critical errors that worsen outcomes:

• Using isotonic saline (0.9% NaCl) as primary fluid - this is the most dangerous error and can precipitate life-threatening hypernatremia 1, 2
• Correcting too rapidly - exceeding 10-15 mmol/L per 24 hours risks cerebral edema 1, 2
• Inadequate monitoring - failing to check sodium levels every 2-4 hours during initial correction can lead to overcorrection 1, 2
• Not accounting for ongoing losses - children with continued vomiting need additional fluid replacement beyond calculated deficits 1
• Using inappropriate beverages - apple juice, Gatorade, and commercial soft drinks should not be used for rehydration 1