Persistent hypernatremia in infant

[Double-Helix, BSN, RN]

Has anyone ever encountered an infant with persistent hypernatremia despite treatment with DDAVP, Diuril, and adequate fluid resuscitation?

History: Full term infant admitted to our hospital after a week long hospitalization for fevers. Treated for sepsis with positive strep culture. Remained febrile after a week of treatment and transferred to us. Febrile on admission, pan cultures and LP with no growth. No fevers since day 1 of admission. Serum sodium was found to be 162 and patient was transferred to PICU. Initially was believed to be dehydration so patient was given boluses with normal saline. Sodium remained unchanged. Next, his fluid deficit was calculated based on a sodium of 165, and he was given that volume. Still no change. Renal and head u/s done. Both unremarkable. Clinically, other than intermittent irritability and tremors, patient had no hypernatremic symptoms.

Over the next couple days of admission the patient began voiding more and more clear, colorless urine. Up to 40 mL/kg/hr. Initially half the urine volume was replaced with 0.45%NS, and shortly we began replacing the full urine volume.

TSH, FSH, LH, free T4, and IGa1 were drawn and WNL. Pitressin challenge was performed with no change in urine osmolality. DDAVP and Diuril were started anyway and formula was changed to PM 60/40 and replacement fluid changed to D2.5 1/3 NS. After 24 hours of treatment, sodium remains in the 160's.

Thoughts?

[meanmaryjean, DNP, RN]

Hmmm..... I'm wracking my brain to come up with an inborn error of metabolism, but I'm stumped.

[Scot21t]

My first comment and I hope I hit the right button. New kidneys that just had a shock of ABX are probably not filtering well to balance. The extra cellular fluid is being evaporated super quick and his/her fast resp also not helping the NA. However if the child is not symptomatic than continue what ya doing and let things catch up. Adults can loose total renal function from infections so let the kid recover. I am sure r/o of DM was already done. I'm more used to hearing about cardiac kids and adults with these issues and they both take time past R/O DM and sepsis.. God bless

[Double-Helix, BSN, RN]

My first comment and I hope I hit the right button. New kidneys that just had a shock of ABX are probably not filtering well to balance. The extra cellular fluid is being evaporated super quick and his/her fast resp also not helping the NA. However if the child is not symptomatic than continue what ya doing and let things catch up. Adults can loose total renal function from infections so let the kid recover. I am sure r/o of DM was already done. I'm more used to hearing about cardiac kids and adults with these issues and they both take time past R/O DM and sepsis.. God bless

That was our first thought, that acute kidney injury was causing the filtration issues. However, if they kidneys were hyperfiltering, shouldn't they also be excreting the electrolytes as well? And if they were hypofiltering, he wouldn't be voiding so excessively. The fact that he's filtering out a lot of water and retaining the electrolytes is more suggestive of DI or some sort of endocrine imbalance.

[KelRN215, BSN, RN]

Congenital nephrogenic DI? DDAVP doesn't work in Nephrogenic DI because the kidneys don't respond to vasopressin in this form of DI. One of the key ways to distinguish nephrogenic DI is whether or not the patient responds to vasopressin.

[NicuGal, MSN, RN]

We see this with really septic kids. The kidneys take a hit and it just takes time to recover. We do replacements until it slows up and the electrolytes start to look better.

[Double-Helix, BSN, RN]

Sorry there hasn't been an update. It did turn out to be nephrogenic DI. Not something you see every day, that's for sure!