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

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

Methods: Prospective observational study of infants born 30-34 weeks gestation at NYU Langone Health between November 2017 and November 2018. Cerebral, renal, and splanchnic rSO were monitored from 12 to 72 h of life, and at seven days. Subjects were divided into gestational age (GA) cohorts. Average rSO, 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.

Results: Twenty subjects were enrolled. The average cerebral rSO ranged from 76.8 to 92.8 %, renal rSO from 65.1 to 91.1 %, and splanchnic rSO 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 (R=0.94) and weakest correlation was in the splanchnic region (R=0.81). The FTOE increased in all three locations over time. Intra-subject variability was lowest in the cerebral region (1.3 % (±1.9)).

Conclusions: 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 rSO in preterm infants.