Well, it is officially cold now and this fact was highlighted during my last shift in the Peds ED when two patients presented with parents concerned for their children having “low temperatures.” This begs the questions (and was actually later inquired by one our the readers of PedsEM Morsels) – At what temperature do I need to “worry” and when I am “worried” what should I do??

What temperature constitutes hypothermia?

• There is some variability in the literature on this topic (naturally… nothing can be easy sometimes)
• Most mention a core body temperature of below 35-35.5˚C (95- 95.9˚F) as the mark of hypothermia
• Others state anything below 36.5˚C (97.7˚F) is abnormal (that seems relatively high to me)
• Much of the literature on environmental exposure related hypothermia use 35˚C, but realize that that might not strictly apply to hypothermia due to infection.
• Because of this, it will likely be necessary to monitor for a trend… and use your judgement.

Once you are satisfied that the neonate is hypothermic, now what?

• First consider the heat losses
  • Conductive (naked baby lying on cold examination table)
  • Convection (cold, drafty rooms and a naked baby don’t go well together)
  • Radiation (supercharged metabolic engines dispursing heat from the large surface area to the surrounding relatively cold environment)
  • Evaporative (particularly problematic for the kid that is wet)
• Neonates are particularly vulnerable to environmental heat losses because of their large body surface to mass ratio, little body fat, and their dependence upon their parents to put them in appropriate environments (sometimes parents didn’t pass the “good parenting” test).

Consider the Broad Categories on the Differential of hypothermia in general:

• Environmental Heat Loss (one of the most common reasons)
• Infection (the one we are all worried about)
• CNS Insults (Intracranial Hemorrhage, trauma, tumors)
• Endo/Met (hypothyroidism, hypoglycemia, DM, Inborn Errors of Metabolism, Addison’s Disease)
• Malnutrition (likely a consideration for the protein deficient children)
• Burns and Exfoliative conditions
• Drugs (examples = ETOH, Narcotics, Barbituates, Atropine, Tylenol)

In my mind, the first 4 are the big ones to consider in a neonate in the ED.

• If the neonate appears truly lethargic or unwell at all, go full court press and do a full sepsis work-up and start antibiotics while considering other possible etiologies like intracranial insults.
• If the child appears well and is alert and vigorous, then obtain a through History paying attention to how the family has been dressing the child and in what environments it has been and for how long.
  • If the history CLEARLY points toward environmental heat losses as the most likely etiology and the child has warmed as expected, then it may be appropriate to educate the family and monitor for a while longer (perhaps admit for a short stay of observation).
  • If, on the other hand, you don’t get a history that truly fits environmental heat loss, then it is most prudent to consider infectious and metabolic etiologies.

• Don’t forget to check a sugar!!

  • Along with infectious etiologies, consider inborn errors of metabolism as an etiology as well.
    • Many times inborn errors of metabolism are missed on initial presentation because we focus on infectious causes and end up masking the true condition.
  • Thyroid studies are easy to get.
  • Look at the calcium level (hypoparathyroidism?)
  • Hyponatremia, hyperkalemia, hypoglycemia – Addison’s disease?
  • Draw extra red tops for your colleagues to test later if needed for other IEMs.

• Consider neuroimaging if there is any abnormal exam findings concerning for intracranial process (trauma or mass?)

Greenberg RA, Rittichier KK. Pediatric nonenvironmental hypothermia presenting to the emergency department: Episodic spontaneous hypothermia with hyperhidrosis. Pediatric Emergency Care: 2003; 19 (1), pp. 32-34.