Written by Clay Smith
Infants ≤60 days of life with hypothermia (< 36 °C) had serious bacterial infection (SBI) 2.8% of the time. There is a suggestion that those 15-28 days with high absolute neutrophil count (ANC) and thrombocytopenia had even greater odds of SBI.
Why does this matter?
We know fever is often bad news in young infants. We know hypothermia is as well. But sometimes infants are exposed too long after a bath and have a transient drop in temperature. Are there other clinical factors that would raise our suspicion for SBI in hypothermic infants ≤60 days?
Hypothermia isn’t cool
This was a retrospective review at a single center over 12 years that identified 360 hypothermic (< 36 °C) infants ≤60 days, of which 2.8% (10/360) had SBI. Using multiple logistic regression, they found three variables that were statistically significant (though a little iffy).
Infants 15-28 days had greater odds of SBI than 0-14 days. aOR 7.60 (95%CI, 1.81-31.86)
“Higher” ANC had greater odds of SBI. aOR 1.25 (95%CI, 1.04-1.50). It was not clear in the full text - “higher” ANC than what? The median ANC in the SBI patients was 2.96 vs. 2.90 in the non-SBI infants; average in the SBI group was 5.19. But there were 7/10 with ANCs 1.6-4.7, which is very reassuring. So, I don’t know how practical this is. We will learn more about ANC cutoffs tomorrow.
Finally, “lower” platelet count also increased odds of SBI. aOR 0.99 (95%CI, 0.99-1.00). Again, I’m not sure - “lower” platelet count than what? Median was 213 in those with SBI; 298 without SBI.
What’s the take home here? Infants ≤60 days with hypothermia had SBI nearly 3% of the time. Although this is a lower rate than in febrile infants, I think we probably need to treat them similarly. If they are over 2 weeks, ANC is really high, or platelet count really low, that’s even more concerning.
Although the podcast won’t drop until next Sunday July 7, Rob Orman has a pretty comprehensive ERcast episode on infant fever you won’t want to miss. This link gets you a discount and JF an Amazon gift card. Nice!
Factors associated with serious bacterial infections in infants ≤60 days with hypothermia in the emergency department. Am J Emerg Med. 2019 Jun;37(6):1139-1143. doi: 10.1016/j.ajem.2019.04.015. Epub 2019 Apr 11.
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