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Cyclical variations in cerebral blood flow velocity.
M Y Anthony1, D H Evans, M I Levene
1Department of Paediatrics, University of Leeds, General Infirmary.
Archives of Disease in Childhood
|January 1, 1991
Summary
Newborn infants exhibit regular, cyclical changes in cerebral blood flow velocity. This finding, observed in both sick and healthy neonates using Doppler ultrasound, adds a new factor to understanding blood flow variations.
Area of Science:
- Neonatal physiology
- Cerebrovascular dynamics
- Medical instrumentation
Background:
- Spontaneous cerebral blood flow changes in neonates are not well understood.
- Existing Doppler ultrasound measurements show wide variations in 'normal' velocity.
- Beat-to-beat variability is a known factor in neonatal cerebral blood flow.
Purpose of the Study:
- To investigate spontaneous changes in cerebral blood flow in neonates.
- To characterize cyclical variations in middle cerebral artery blood flow velocity.
- To differentiate new cyclical variations from known beat-to-beat variability.
Main Methods:
- Utilized a newly developed online Doppler technique for continuous insonation.
- Monitored middle cerebral arteries in sick (n=20) and healthy (n=16) term infants.
- Analyzed 290 one-minute recordings of blood flow velocity and simultaneous blood pressure.
Main Results:
- Pronounced, regular, cyclical variations in cerebral blood flow velocity were observed.
- These cycles occurred 1.5-5 times per minute.
- Cyclical variations were present in 95% of sick infants and 94% of healthy neonates, independent of systemic blood pressure fluctuations.
Conclusions:
- Identified a novel, regular, cyclical variation in neonatal cerebral blood flow velocity.
- This cyclical variation is distinct from beat-to-beat variability.
- These findings provide an additional explanation for the wide range of 'normal' Doppler ultrasound recordings in neonates.