Abstract
Background
Therapeutic hypothermia is a standard of care for neonatal encephalopathy; however, approximately one in two newborn infants fails to respond to this treatment. Recent studies have suggested potential relationships between body temperature, heart rate and the outcome of cooled infants.
Methods
The clinical data of 756 infants registered to the Baby Cooling Registry of Japan between January 2012 and December 2016 were analysed to assess the relationship between body temperature, heart rate and adverse outcomes (death or severe impairment at 18 months corrected age).
Results
A lower body temperature at admission was associated with adverse outcomes in the univariate analysis (P < 0.001), the significance of which was lost when adjusted for the severity of encephalopathy and other covariates. A higher body temperature during cooling and higher heart rate before and during cooling were associated with adverse outcomes in both univariate (all P < 0.001) and multivariate (P = 0.012, P < 0.001 and P < 0.001, respectively) analyses.
Conclusions
Severe hypoxia–ischaemia might be a common causative of faster heart rates before and during cooling and low body temperature before cooling, whereas causal relationships between slightly higher temperatures during cooling and adverse outcomes need to be elucidated in future studies.
Impact
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In a large cohort of encephalopathic newborn infants, dual roles of body temperature to the outcome were shown; adverse outcomes were associated with a lower body temperature at admission and higher body temperature during cooling.
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A higher heart rate before and during cooling were associated with adverse outcomes.
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Severe hypoxia–ischaemia might be a common causative of faster heart rates before and during cooling and low body temperature before cooling.
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The exact mechanism underlying the relationship between slightly higher body temperature during cooling and adverse outcomes remains unknown, which needs to be elucidated in future studies.
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Acknowledgements
The authors are grateful to the staff of participating centres for their contribution to the data collection, the infants and their parents for sharing the clinical information. This work was supported by the Japan Society of Perinatal and Neonatal Medicine, and the Ministry of Health, Labour and Welfare, Japan (H27-001, Special research in perinatal medicine). K.T. is funded by the Japan Science and Technology Agency and the Ministry of Education, Culture, Sports, Science and Technology (Grant-in-Aid for Scientific Research 18K15722). J.S. was funded by the Japan Science and Technology Agency and the Ministry of Education, Culture, Sports, Science and Technology (Grant-in-Aid for Scientific Research C20K08247). S.I. was funded by the Japan Science and Technology Agency and the Ministry of Education, Culture, Sports, Science and Technology (Grant-in-Aid for Scientific Research C18K09955). O.I. was funded by the Japan Science and Technology Agency and the Ministry of Education, Culture, Sports, Science and Technology (Grant-in-Aid for Scientific Research A20H00102).
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K.T., S.I., M.N. and O.I. designed the study and the survey items. All authors participated in the data collection. K.T., T. Isayama, S.I. and O.I. performed the statistical analyses. K.T., J.S., T. Isayama, A.T., T.M. and O.I. contributed to the interpretation of the findings. K.T., J.S. and O.I. drafted the manuscript. All authors critically reviewed and revised the manuscript and gave the final approval of the published version. All authors agree to be accountable for all aspects of the work.
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The ethics committees approved that parental consent was not needed for the registry, since no patient identifier was collected.
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Tsuda, K., Shibasaki, J., Isayama, T. et al. Body temperature, heart rate and long-term outcome of cooled infants: an observational study. Pediatr Res 91, 921–928 (2022). https://doi.org/10.1038/s41390-021-01502-w
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DOI: https://doi.org/10.1038/s41390-021-01502-w
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