A recent study hypothesized that the heart rate (HR) variation in an acute setting compared with HR in well-being status is a good marker of dehydration and acute kidney injury (AKI). Since HR in well-being status is unknown in most cases, the study assumed, as a reliable surrogate, the 50th percentile of HR according to age and gender. It evaluated if the estimated percentage of heart rate variation in an acute setting compared with the 50th percentile of HR (EHRV) could be a marker of dehydration and AKI in children. 

It included two independent cohorts, one prospective comprehending 185 children at type 1 diabetes mellitus onset (derivation) and one retrospective comprehending 151 children with acute gastroenteritis and pneumonia (validation), to develop and externally validate EHRV as a predictor of the ≥ 5% dehydration and/or AKI composite outcome. The study excluded Febrile patients. It measured EHRV as ((HR at admission–50th percentile of HR)/HR at admission) × 100. 

The study found:

• The prevalences of ≥ 5% dehydration and AKI as- 

•    61.1% and 43.8% in the derivation 

•    34.4% and 24.5% in the validation cohort. 

• For the ≥ 5% dehydration and/or AKI composite outcome-

•    the area under the receiver-operating characteristic curve of the EHRV in the derivation cohort as 0.69, 

•    the best EHRV cut-off as > 24.5%. 

• In the validation cohort EHRV > 24.5% showed-

•    specificity = 100%, 

•    positive predictive value = 100%, and 

•    negative predictive value = 67.1%. 

• The positive likelihood ratio was infinity, and the odds ratio was not calculable since all the patients with EHRV > 24.5% had ≥ 5% dehydration and/or AKI.

This study describes EHRV as a reliable marker of dehydration and AKI. However, the study necessitates further validations to allow the implementation of EHRV in clinical practice.

Marzullo P, Di Sessa A, Iafusco D., et al. Heart rate cut-offs to identify non-febrile children with dehydration and acute kidney injury. Eur J Pediatr. 2022;181:1967–1977. https://doi.org/10.1007/s00431-022-04381-3