UMEM Educational Pearls

Category: Pediatrics

Title: Pediatric Electrolytes: Approach to Hyponatremia

Keywords: pediatrics, electrolyte, sodium (PubMed Search)

Posted: 7/5/2024 by Kathleen Stephanos, MD (Emailed: 9/6/2024) (Updated: 9/6/2024)
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Continuing with the electrolyte derangements in children: Hyponatremia 

Hyponatremia is defined as a Sodium of less than 135 mmol/L and does not depend on patient age.  

This is the most common electrolyte abnormality in pediatric patients. Excessive free water is often the culprit and is usually thought of in the neonate or infant whose guardians are mixing formula incorrectly. * Additional causes include inappropriate ADH (Antidiuretic hormone) secretion, or in the case of dehydrated patients appropriate ADH secretion. Sodium wasting is rare.  

Total body water (TBW) is important to consider, and preterm neonates have higher TBW (80%) than full term (70%) and 1 year old infants (~60%) putting them at higher risk of hyponatremia.  

Recognizing the volume status of the patient aids in determining the etiology of the hyponatremia and allows for appropriate treatment. This may require obtaining urine sodium.  

Treatment: 

Hypertonic saline should be used only for patients with severe neurologic complications including seizures or altered mentation. In these patients, a hypertonic saline bolus should be given at 3-5 ml/kg of 3% NaCl over 10-15 minutes.  

In hypovolemic patients without neurologic symptoms, fluid resuscitation is the mainstay with caution to increase sodium levels by no more than 6-8mmol/L/day. For euvolemic or hypervolemic patients, fluid restriction is advised.  

Prevention: 

Importantly, when children receive IV fluids, the choice should be made to select isotonic fluids (0.9% NaCl) rather than hypotonic fluids (0.45% NaCl) to avoid iatrogenic development of hyponatremia.  

*Reminder: 2 ounces (about 60 ml) of water should be placed in the bottle, and then 1 full scoop of formula, unless directed to have higher caloric content by their doctor- in which case the amount of formula in the mixture should be higher

References

Saba L, Hanna C, Creo AL. Updates in hyponatremia and hypernatremia. Curr Opin Pediatr. 2024 Apr 1;36(2):219-227. doi: 10.1097/MOP.0000000000001324. Epub 2024 Jan 4. PMID: 38174733.

Brown DH, Paloian NJ. Hypokalemia/Hyperkalemia and Hyponatremia/Hypernatremia. Pediatr Rev. 2023 Jul 1;44(7):349-362. doi: 10.1542/pir.2021-005119. PMID: 37391630.