Changes in regional tissue oxygen saturation values during the first week of life in stable preterm infants

Near infrared spectroscopy (NIRS) is a non-invasive method for monitoring regional tissue oxygen saturation (rSO₂). The purpose of this study is to investigate the changes that occur in cerebral, splanchnic, and renal rSO₂ and fractional tissue oxygen extraction (FTOE) in stable preterm infants in the first week of life.

Prospective observational study of infants born 30-34 weeks gestation at NYU Langone Health between November 2017 and November 2018. Cerebral, renal, and splanchnic rSO₂ were monitored from 12 to 72 h of life, and at seven days. Subjects were divided into gestational age (GA) cohorts. Average rSO₂, splanchnic cerebral oxygen ratio (SCOR), FTOE, and regional intra-subject variability was calculated at each location at five different time intervals: 0-12 h, 12-24 h, 24-48 h, 48-72 h, and one week of life.

Twenty subjects were enrolled. The average cerebral rSO₂ ranged from 76.8 to 92.8 %, renal rSO₂ from 65.1 to 91.1 %, and splanchnic rSO₂ from 36.1 to 76.3 %. The SCOR ranged from 0.45 to 0.94. The strongest correlation between the GA cohorts was in the cerebral region (R²=0.94) and weakest correlation was in the splanchnic region (R²=0.81). The FTOE increased in all three locations over time. Intra-subject variability was lowest in the cerebral region (1.3 % (±1.9)).

The cerebral region showed the strongest correlation between GA cohorts and lowest intra-subject variability, making it the most suitable for clinical use when monitoring for tissue hypoxia. Further studies are needed to further examine rSO₂ in preterm infants.