Temperature to heart rate relationship in the neonate

In neonatal intensive care, measurement of heart rate is part of every clinical examination and it is used for monitoring hemodynamic status. However, it is influenced by some exogenous and endogenous factors, such as medication, pain, and stress. (1) Similarly, an increased heart rate is a normal physiological response to fever. Heart rate is known to increase by 10 beats per minute (bpm) per degree centigrade increase in body temperature in children. (2) In order to allow physicians to identify patients who have a higher heart rate than would be expected for a given level of temperature, Thompson et al. (3) created temperature specific heart rate centile charts adaptable to children from three months to ten years. Very few data exist on the relationship of temperature and heart rate in younger infants. The only study on this topic so far was performed in an emergency department that included infants up to the age of 12 months, where they found no linear correlation between fever and heart rate in the group of infants younger than two months. (4) To our knowledge no studies have ever addressed this issue in newborns.