Background: Data on cHbc obtained with NIRS depend on the technique used and interindividual comparison is problematic. To overcome this drawback we used a recently developed method (Critikon 2020) involving a sensor with fixed geometry to assess a trend in cHbc during the first day of life and to identify associated factors.

Subjects: 26 preterm infants (gestational age: range 24 - 34 weeks, median 27 4/7; birthweight: range 660-2290 g, median 1020 g).

Methods: Near infrared spectroscopy (Critikon 2020) with a sensor fixed in the fronto-parietal region was carried out three times (1-6 hrs, 12-16 hrs, 24-28 hrs after birth) in all infants.

Results: CHbc was 44.1 μmol (interquartile range 32.3 - 52.8μmol) and increased significantly during 24 h (mean increase 0.51μmol/h; p=0.036). There was no correlation between the size of this increase and gestational age, birth weight or head circumference. None of the following variables was significantly associated with cHbc (univariate and multivariate analysis): heart rate, mean arterial blood pressure, blood glucose, haemoglobin, arterial oxygen saturation (SO2), arterial CO2.

Conclusion: CHbc increases in the first 24 hours independently of blood pressure, heart rate, arterial CO2, SO2 glucose and haemoglobin.