Background: As it has been reported that bladder voiding in sleeping full-term infants is consistently accompanied by a cortical arousal, it was the aim of the present study to find out whether this could also hold true for preterm infants.
Methods: Polygraphic recordings were performed in 21 healthy preterm infants (10 female). The infants' gestational age at birth was 31+/-2.7 weeks and postnatal age at study entry was 26+/-8 days (mean+/-standard deviation). Bladder voiding was recorded by an adapted enuresis detector which was connected to the polygraphic computer unit. Arousals were defined as suggested by the International Paediatric Work Group on Arousals.
Results: Bladder voiding was recorded 50+/-7 min after sleep onset and occurred during quiet sleep (QS) only. Heart rate (HR), respiratory frequency (RF) and electroencephalographic (EEG) frequency did not change during bladder voiding. Body movements were recorded in 52% of all preterm infants.
Conclusion: We found that bladder voiding was not accompanied by arousals, suggesting that the arousal process in preterm infants may be delayed due to immaturity.