Birth prematurity determines prolonged autonomic nervous system immaturity

Abstract

Because of its multiple involvement in physiological processes, autonomic nervous system (ANS) activity, a key regulator of homeostatic control, demonstrates a progressive increase during pregnancy. The profile of its maturation, mainly in the parasympathetic arm, in premature or full term infants, may help us to better understand its pathophysiological role. We prospectively evaluated ANS maturity in a group of 23 premature (PREM) infants at their theoretical term age and in 8 full term (FT) newborns. All recordings were registered close to the theoretical full term period (from 38 to 41 weeks) for the PREM group and during the first week of life for the FT newborns. Polygraphic recordings, EEG monitoring associated with visual clinical control, and Holter ECG, were performed simultaneously. ANS indices were then calculated during quiet sleep periods, using Wavelet transform of RR (beat to beat) intervals. High frequency components were found to be significantly lower in the PREM than in the FT group (p<0.05). Furthermore, at theoretical full term age, the greater the prematurity, the lower was parasympathetic activity. Because it is easy, monitoring of parasympathetic activity may help us to understand autonomic maturation and its clinical prognostic implications.

Decreased heart rate variability in children born with low birth weight

“…However, when the same subjects were re-investigated at 2-3 and 6-7 y, no significant difference in HRV parameters persisted in comparison with the controls (16). The impairment in ANS function among the group of premature infants was suggested to be an effect of stress owing to pain, noise, visual stimuli, inadequate nutrition, and ventilator support (17)(18)(19). It is known that the sympathetic nervous system matures earlier in fetal life than the parasympathetic nervous system but then becomes increasingly outbalanced beyond 30 wk of gestational age, which could explain a temporary dominance of the sympathetic system at the beginning of life for children born PT (19,20).…”

“…The impairment in ANS function among the group of premature infants was suggested to be an effect of stress owing to pain, noise, visual stimuli, inadequate nutrition, and ventilator support (17)(18)(19). It is known that the sympathetic nervous system matures earlier in fetal life than the parasympathetic nervous system but then becomes increasingly outbalanced beyond 30 wk of gestational age, which could explain a temporary dominance of the sympathetic system at the beginning of life for children born PT (19,20). Even in children born SGA, higher sympathetic tone and lower vagal tone has been observed postnatal at 1 and 3 mo of age (5).…”

Cardiovascular Consequences of Preterm Birth in the First Year of Life

“…In addition, HF power showed the greatest increase from the preterm to term group, while LF power showed equal differences from preterm to intermediate and intermediate to term indicating that there is a steep increase in vagal tone at 37-38 wks ConA which plateaux to term and a steady increase in sympathetic tone from 31-41 wks (Clairambault et al, 1992). In a similar study of preterm infants divided into groups of 25-27, 28-31, and 32-37 weeks GA and studied at term CA compared with full term infants, it was found that all three groups of preterm infants had significantly lower HF power values in quiet sleep compared to the term infants (Patural et al, 2004). Furthermore, preterm infants had lower parasympathetic activity at term CA.…”

“…The study demonstrated a decrease in heart rate in quiet sleep with increasing chronological age. In addition, in both quiet sleep and active sleep there was an increase in both time and frequency domain measures of HRV, indicating that there was a maturation of autonomic cardiovascular control during this period before term (Patural et al, 2004).…”

Neonatal Hypotension, the Role of Hydrocortisone and Other Pharmacological Agents in its Management

“…Hypovolemia as a primary cause is observed less frequently [6]. Since the autonomic nervous system that regulates the peripheral systemic resistance is immature in preterm infants [7], these patients are likely to develop peripheral vasodilatation and hypotension [6]. In addition, the immature myocardium of a preterm infant also has less mitochondria than a term infant.…”