What factors contribute to hypernatremia in newborns and how is it treated?

• A. Overhydration with hypotonic fluids.
• B. Excessive salt intake.
• C. No fluids are required; monitor only.
• D. Inadequate breastfeeding or dehydration; treat with isotonic fluids and careful sodium correction.

Answer: (D)

Hypernatremia in newborns usually comes from loss of free water relative to sodium, most often due to dehydration from inadequate fluid intake. In newborns, this is frequently tied to breastfeeding difficulties or insufficient feeding, so the baby isn’t getting enough volume to meet needs. When the body loses more water than sodium, serum sodium rises, and the infant can become irritable, lethargic, or have poor feeding and fewer wet diapers.

The best approach is to restore intravascular volume with isotonic fluids and then correct the elevated sodium gradually. Starting with an isotonic solution, such as 0.9% saline, helps replete the extracellular fluid without causing abrupt shifts in serum osmolality. After volume status improves, sodium should be lowered slowly to avoid cerebral edema; a careful rate is important, typically aiming for a gradual decrease over 24 hours and not correcting too fast. Throughout this process, monitor serum sodium, potassium, and glucose, as well as urine output, weight, and signs of fluid balance.

Why the other scenarios aren’t appropriate: giving hypotonic fluids would lower sodium too quickly and can worsen brain swelling or edema; simply stopping fluids and monitoring won’t address the dehydration and could allow sodium to remain high or rise further; excessive salt intake is a possible cause but is not the typical scenario in newborns and does not address the immediate need to restore hydration and correct sodium safely. The key is inadequate intake with dehydration and treatment focused on isotonic rehydration and controlled sodium correction.