Written by Gabby Leonard
Given the prevalence of serious infection, this review suggests hypothermic infants (<36.5oC, 97.7oF) ages 60 days or younger need a sepsis workup.
Why does this matter?
One key factor in diagnosing sepsis is temperature abnormalities, including hypothermia. Due to immature immune systems, hypothermia alone could indicate serious infection in young infants and may warrant a full septic workup. We covered a study which found the prevalence of serious infection was 2.6% (hypothermia defined as <36 °C, 96.8 °F), and all septic infants had other red flag symptoms. Another study we covered found infants ≤60 days of life with hypothermia (< 36 °C) had serious bacterial infection (SBI) 2.8% of the time. How prevalent was serious infection in this review?
Ice, ice baby…
This study was a systematic review of 4 studies (two of which we covered previously on JF), totalling 648 infants 60 days or younger with hypothermia (<36.5oC) and workup for serious infection (SI) including bacteremia, UTI, meningitis, HSV or pneumonia. The WHO defines hypothermia in infants as <36.5oC, which was the definition used in this review, but definitions vary, and many studies use a lower cutoff of <36.0oC (<96.8oF). The overall prevalence of SI was 4.86% (95%CI 1.97 to 8.82), with UTI being the most common source. Infants 28 days or younger had a prevalence of 5.15%. Additionally, 41.7% of hypothermic infants with SI were diagnosed within the first week of life. While this appears to be a high prevalence, it may be falsely elevated due to a significant number of infants who were hypothermic on presentation but did not receive a full septic workup and, therefore, were not included in these results. Infants are more susceptible to low temperatures due to their large surface area to body mass ratio, inability to shiver, and low glycogen stores. Authors mentioned several alternative etiologies for hypothermia that should be considered, including environmental exposure after being undressed for physical exam, inborn errors of metabolism, cardiomyopathy, hemorrhagic encephalitis, dehydration, FTT and BRUE.
Editor’s note: Temperature cutoffs vary; some define it as <36oC. Know your local numbers. If hypothermic for obvious reasons, such as exposure to cool temperatures while uncovered, it’s reasonable to bundle, watch and wait, assuming they’re well appearing. If no good explanation, it’s best to go ahead with a sepsis workup, similar to what would be done for febrile infants of a similar age. ~Clay Smith
The Prevalence for the Risk of Serious Infection in Hypothermic Infants ≤ 60 Days: A Systematic Review. Acad Emerg Med. 2022 Jun 6. doi: 10.1111/acem.14547. Online ahead of print.