Transitional Changes in Cerebral Blood Volume at Birth

Background: Near-infrared spectroscopy (NIRS) enables non-invasive measurements of changes in the concentration of oxygenated (ΔHbO₂) and reduced (ΔHbR) haemoglobin. Changes in total haemoglobin (ΔHbT = ΔHbO₂ + ΔHbR) provide information on changes in cerebral blood volume (CBV). Objective: The aim was to evaluate the behaviour of CBV during immediate postnatal transition in term infants. Design: This observational study was conducted at the Medical University of Graz. NIRS measurements were carried out in term infants without need for respiratory support by using ‘NIRO 200-NX' (Hamamatsu) over the first 15 min after birth. Results: 109 infants with a mean gestational age of 38 + 6 weeks (±7 days) and birth weight of 3,242 g (±481) were included. Related to a reference value at minute 15, a significant decrease of HbT was observed for each minute within the study period. The mean (±SD) decrease of HbT of 17 (±40) µmol/l from minutes 2 to 15 represents a decrease of CBV of 1.0 ml/100 g brain (±2.2). Conclusions: In healthy newborns, CBV decreased over the whole study period. This likely reflects a physiological process. The impact and clinical relevance of different CBV behaviour during immediate transition needs to be investigated in further studies.