Normal blood pressure values in the neonate

The generally available blood pressure norms in children are mainly based on data from studies of populations of children over 1 year of age. Data on blood pressure values in the youngest age groups are limited. In addition to the problems of selecting a group that can serve as a reference population, the measurement methodology and the different measuring devices used is a major problem. As oscillometric devices are now generally used in practice, it would be appropriate to rely on standards developed using oscillometric measurement. Thus, the assessment of mean arterial pressure (MAP) should be introduced into clinical use, as only this parameter of the pulse wave is directly calculated during oscillometric measurement. Furthermore, MAP corresponds to perfusion pressure and the assessment of this parameter avoids making decisions based on the analysis of systolic blood pressure (SBP) in children with fluctuating blood pressure values, which may be elevated due to stress reactions. The following is an outline of the history of research on blood pressure standards in neonates and preterm infants, including measurement methodology.

Studies in older children have shown an association of BP height with patient age, height and weight, while in neonates, BP values have been observed to increase with gestational age, calendar age and birth weight. Arterial pressures in term newborns, neonates born by caesarean section, or those with asphyxia tend to be higher in the first 2-3 hours of life, after which they decrease. The situation is different for premature babies or babies with low Apgar scores, in whom blood pressure at birth is relatively low and gradually increases in the first 6 hours of life. As most of the information on blood pressure in neonates and infants comes from intensive care centres, these data are subject to error due to additional patient burdens that may affect blood pressure (CPAP, inotropic drugs). In addition, inaccuracies in the existing standards are due to differences in the measurement technologies used (direct, oscillometric, Doppler measurements).

Among the first blood pressure norms in the youngest age group are those published by De Swieta et al. Based on Doppler blood pressure measurements taken in 500 newborns, in addition to confirming the already known phenomenon of an increase in blood pressure in the first days and weeks of life, he also found a correlation between the child's activity status and blood pressure levels and described a significant drop in blood pressure during sleep. Furthermore, in his subsequent work, De Swiet highlighted the phenomenon of 'tracking', i.e. the tendency to maintain centile BP values as the child grows and matures. However, while a correlation was found between BP values at 4 days of age and 6 weeks of age, this relationship was not confirmed at subsequent intervals. The Brompton Study, on the other hand, showed that although the 'tracking' phenomenon starts between 1 and 5 years of age, significant correlations are only observed after 3 years of age. Thus, the risk of developing hypertension at a later age is related not so much to blood pressure values at the neonatal age, but to existing burdens affecting blood pressure control such as gestational age, birth weight, postnatal weight gain, perinatal programming and underlying diseases (kidney disease, coarctation of the aorta). In contrast, the true 'tracking' phenomenon is only relevant from the pre-school-school period onwards and increases with age, reaching its strongest correlation in adolescence.