[Sudden infant death. Postmortem flow measurements in the large vessels of the neck for the demonstration of posture-dependent cerebral hypoxemia].

The concept of position-dependent cerebral hypoxaemia as a mechanical cause of sudden death in infants is based on the possibility of flow impairment in the large neck vessels (carotid and vertebral arteries) on marked rotation and (or) flexion of head and neck. To test this hypothesis systematic flow measurements were performed post-mortem with 21 different angles of head and neck in 16 infants who had died suddenly. The angles chosen were those taken especially during sleep with the infant in a prone position. The measurements demonstrated flow impairment, especially as a result of mechanical narrowing of both vertebral arteries. On the other hand, the range of variation in the internal carotid artery was marked and individual circumstances could not be estimated. There was no certain connection between flow impairment in the vertebral artery and possible increase in the carotid artery. The least dangerous extreme movement for an infant is dorsal flexion of the neck with reclining of the head, a favoured position of many infants. Particularly dangerous is flexion combined with rotation. Judged by the number of complete flow stoppages in the vertebral and carotid arteries, the danger is greatest with rotation in dorsal flexion. Since the dangers of supine position have been known for a long time, lateral position is urgently recommended as the sleeping position in infants.