Renal oxygenation measured by near-infrared spectroscopy in preterm neonates in the first week

Abstract

Objective: To describe renal regional saturation of oxygen (RrSO₂) values during the first week of life for preterm neonates born at <32 weeks gestational age (GA).

Methods: RrSO₂ values recorded over the first week of life using near-infrared spectroscopy were retrospectively analyzed in this two-center cohort study of preterm infants without known congenital anomalies of the kidney.

Results: A cohort of 109 neonates with a median GA of 26.9 weeks and a median of 120 (IQR: 87-141) hours of continuous RrSO₂ monitoring were included. Separately fitted trends in RrSO₂ did not differ (p = 0.52) between sites and demonstrated a consistent decrease in RrSO₂ by 20 points (95% CI: 9.6-30.1) during the first 60 h of life, followed by a stabilization of RrSO₂ thereafter. RrSO₂ baseline trends increased by 2.1 (95% CI: 0.8-3.3) percentage points for each additional week GA between 24 and 32 weeks GA.

Conclusions: Despite differences in adjusted RrSO₂ values between sites, profiles over time are consistent, allowing for the determination of RrSO₂ trajectories in preterm infants. This expected pattern of RrSO₂ changes in the first week may help guide future investigations and interventions to identify and reduce kidney injury in the preterm neonate.

Impact: Renal regional saturation of oxygen (RrSO₂) slowly decreases during the first 60 h of age in <32-week preterm neonates. While site differences were identified with respect to absolute values, RrSO₂ trends from two different centers were not different. Lower gestational age neonates have lower RrSO₂ levels during the first week.

Figure 1:

Center RrSO₂ means (a&b) – Solid line tracing indicates the mean RrSO₂ over time with pointwise 95% confidence limits for the mean at each HOL given by dashed lines; gray points are individual measurements from each neonate at the centers. Overall common behavior RrSO₂ means (c) – Each center represented with red (UnityPoint Health-Meriter Hospital) and black (Lucile Packard Children’s Hospital Stanford) with shaded regions representing the 95% confidence intervals for the mean RrSO₂.

Figure 2:

Change in percent RrSO₂ – shown over several early (2–60 HOL) and later (60–168 HOL) time intervals. Solid symbol is the average change with 95% CI as whiskers; intervals for which the 95% CI excludes zero (horizontal dashed line) are significant at the 0.05 level.

Figure 3:

Mean RrSO₂ by gestational age – with shaded regions representing the 95% confidence intervals for the mean RrSO₂.