Original articleIs bladder voiding in sleeping preterm infants accompanied by arousals?
Introduction
It was previously assumed that bladder voiding in infants is induced by a constant bladder-filling volume and that it is not influenced by the brain, and is, therefore, independent of behavioural state. Recently, however, it was shown that the neonatal brain is involved in the regulation of bladder function [1], [2].
Furthermore, it has been shown that bladder voiding in sleeping infants is consistently accompanied by a cortical arousal, reflected by body movements, increase in heart rate (HR) and an increase in electroencephalographic (EEG) frequency [3]. This arousal may be considered to be a short and incomplete change in behavioural state [4]. Arousal from sleep is an important protective response to a life-threatening event. One of the current leading hypotheses to explain sudden infant death syndrome (SIDS) is a failure of the infants to arouse [5]. Supporting this idea is the finding that one of the few indicators in prospective studies that distinguish infants who subsequently died of SIDS from healthy infants was the occurrence of fewer body movements during sleep in the SIDS infants, indicating fewer episodes of spontaneous arousal [6].
As cortical arousals during bladder voiding have been described in full-term infants at the age of one month and as the actual literature lacks any information about whether this could also hold true for preterm infants, it was the aim of this study to find out whether bladder voiding in sleeping preterm infants is accompanied by any arousal reaction.
Section snippets
Subjects
Polygraphic recordings were performed during undisturbed daytime naps in 21 healthy preterm infants (10 female, 11 male). The infants’ gestational age at birth was 31.6 ± 2.7 weeks and postnatal age at study entry was 26 ± 8 days; birth weight was 1698 ± 492 g and actual weight at study entry was 2062 ± 250 g (mean ± standard deviation). None of these preterm infants showed any neurological deficits at the time of polygraphic recording. Apgar scores 1, 5, and 10 min after delivery were 8.57 (±0.17), 9.90
Results
Mean polygraphic recording time was 2.5 (±0.1) h and mean time spent in AS, QS, and intermediate sleep (IS) was 42 ± 0.6%, 40 ± 0.8%, and 18 ± 1.2%, respectively. Bladder voiding was recorded at a mean time of 50 ± 7 min after sleep onset and occurred during QS only. When comparing EEG frequency, no significant difference in HR and RF before and after the onset of bladder voiding was found. This was true when comparing raw figures as well as percentage of modification (for details, see Table 1).
Bladder
Discussion
Our main finding was that bladder voiding in sleeping preterm infants was not accompanied by arousals.
Events such as body movements, changes in HR, EEG frequency, and RF occur during sleep in infants and are essential for cardiopulmonary homeostasis and normal development [11], [12]. These events indicate arousals and are defined by the International Paediatric Work Group on Arousals [10]. It has been shown that the characteristics of arousals change with age [13]. Therefore, the arousal
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