Ventilator-associated sinus arrhythmia in a preterm neonate--an indicator for a mature autonomic nervous system?

Heart rate variability responses of a preterm infant to kangaroo care

OBJECTIVE

To examine the effect of kangaroo care on heart rate variability in a healthy preterm infant.

DESIGN

Case study.

SETTING

Private room on a postpartum unit.

PARTICIPANT

A mother-preterm infant dyad.

INTERVENTION

Kangaroo (skin-to-skin) care.

MAIN OUTCOME MEASURE

Heart rate variability, a noninvasive measurement of the sympathetic and parasympathetic components of the autonomic nervous system's influence on heart rate.

RESULTS

Heart rate variability, especially the parasympathetic component, was high when the infant was fussy in the open crib, indicating increased autonomic nervous system activity. With kangaroo care, the infant fell asleep, and both sympathetic and parasympathetic components of heart rate variability decreased.

CONCLUSIONS

The wide fluctuations in the parasympathetic component of heart rate variability suggest immaturity of the sympathovagal response. Overall, kangaroo care produced changes in heart rate variability that illustrate decreasing stress.

Birth prematurity determines prolonged autonomic nervous system immaturity

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.

Heart Period Variability of Intubated Very-Low-Birth-Weight Infants During Incubator Care and Maternal Holding

• Background Heart rate has been used to measure infants’ physiological stability during skin-to-skin holding. Variability in heart period (interbeat interval), a more sensitive measure of autonomic nervous system tone, has not.

• Objective To describe heart period variability in intubated very-low-birth-weight infants during incubator care and during maternal skin-to-skin holding.

• Design/Methods An experimental, interrupted time series, crossover design was used; infants served as their own controls. Infants were randomly assigned to treatment order: 2 hours of intermittent skin-to-skin holding for 2 consecutive days followed by 2 days of incubator care or vice versa. The analog signal representing heart period was sampled and quantized at 5 Hz via a dedicated computer system in multiple 300-second epochs each day.

• Results Fourteen infants with similar characteristics completed the protocol. The mean interbeat interval was 332 ms during skin-to-skin care and 368 ms during incubator care. Power within the low-and high-frequency regions of heart period was not significantly different between skin-to-skin holding and incubator care. Mean low-frequency power was 124.6 ms2 during skin-to-skin holding and ranged from 51.9 ms2 to 71.4 ms2 during all periods of incubator care. Mean high-frequency power was similar during skin-to-skin holding and incubator care (8.8 ms2 and 6.1 ms2). Infants of 32 to 34 weeks’ corrected gestational age had increased power in the low- and high-frequency regions.

• Conclusions Heart period variability did not improve during skin-to-skin holding. Gestationally older infants had increased power in the low- and high-frequency regions, suggesting a maturing autonomic nervous system.