Position dependent changes of cerebral blood flow velocities in premature infants

The supine or prone positioning of infants has been a cause of much controv ersy. Recently it has been postulated that the position dependent hypoperfu sion of the brainstem represents a possible cause of sudden infant death. T o demonstrate position dependency and maturational changes of cerebral perf usion in premature newborn infants we investigated cerebral blood flow velo cities (CBFV) in the main supratentorial and brainstem cerebral arteries. M easurements of CBFV were done with transfontanellar colour-coded Doppler so nography in the internal carotid artery (ICA), basilar artery (BA), and ver tebral artery (VA) in the prone (head centered-baseline) and supine positio ns (maximal rotation to both sides) in 23 premature infants aged between 3- 5 days of life. We performed follow-up measurements in 17 infants 7-10 days later and in 16 infants at the corrected age of 1 month. There was no diff erence in mean CBFVs between the prone and supine position at the first inv estigation. At the third investigation, CBFVs were significantly higher in the supine compared to the prone position. The CBFVs of the ICA were higher than in the BA and VA. This difference was not influenced by the body posi tion but increased with post-natal age more in the VA (159%) than in the BA (129%) and ICA (128%). Position dependency was not seen in the ICA perfusi on. In the prone position, five infants showed an incomplete steal effect i n the contralateral VA. There was no significant side difference in the CBF Vs. of the ICA and VA, but in the resistance indices in the VA (left > righ t). Conclusion: in premature newborns, position dependent changes of cerebr al blood flow velocity develop with maturation and are most pronounced in t he vertebrobasilar system. These changes are possibly due to compression of the vertebral artery by neck movement and suggest an individual risk of br ainstem perfusion deficits that may be aggravated with age and head rotatio n in a prone position.