CEREBRAL BLOOD VELOCITIES AND THEIR VARIABILITY IN DIFFERENT SLEEP STATES IN THE NEWBORN INFANT

Abstract

This study was planned to determine the variability of cerebral arterial blood velocities in normal newborn infants. Velocities were measured in intracranial arteries and the internal carotid artery using pulsed bidirectional doppler ultrasound in 15 fullterm infants, 4-5days old, in both active (REM) and quiet (NREM) sleep continuously for periods of 1 to 6 mins. without movements. The doppler signals were analysed by computer and the time averaged mean velocity calculated per consecutive heartbeat. Internal carotid artery velocities always varied more in REM than NREM sleep (mean c.v. 8.4% v 6.3%) but this difference was less marked in the intracranial arteries (mean c.v. 8.5% v 7.5%). In both states sudden spontaneous increases and decreases in velocities occurred (most often in REM) and also regular cyclical variations (most often in NREM) at 2-5c/s and 35-45c/s. The latter was clearly related to respiratory rate. Heartrate also varied considerably, sometimes in phase with, sometimes independently of the velocity variations such that it was not possible to conclude that velocity variations were always secondary to heartrate fluctuations. Cyclical velocity variations were most marked in periods of quiet regular or periodic breathing and may be the results of interactions between the central and peripheral control of respiration, blood pressure and temperature.