Correlation of Renal Tissue Oxygenation to Venous, Arterial, and Capillary Blood Gas Oxygen Saturation in Preterm Neonates

Abstract

Objective: The aim of the study is to assess the correlation of renal regional tissue saturation of oxygen (RrSO₂) measured by near-infrared spectroscopy (NIRS) in preterm neonates to venous oxygen saturation (SvO₂) obtained from umbilical venous catheters (UVCs), arterial oxygen saturation (SaO₂) obtained from umbilical artery catheters (UACs), and capillary oxygen saturation (ScO₂) from capillary heel blood draws.

Study design: A secondary analysis of a prospective RrSO₂ monitoring study in preterm neonates born <32 weeks gestational age. Neonates with any blood gas obtained during RrSO₂ monitoring were included. RrSO₂ was compared with simultaneous O₂ saturation using non-parametric Mann Whitney U-test and Spearman correlation coefficient.

Results: In 35 neonates, 25 UVC, 151 UAC, and 68 heel capillary specimens were obtained. RrSO₂ was lower than the median SvO₂ (58.8 vs. 78.9, p <0.01), SaO₂ (51.0 vs. 93.2, p <0.01), and ScO₂ (62.2 vs. 94.25, p <0.01). RrSO₂ values correlated to both SaO₂ and ScO₂ (r = 0.32; p <0.01, r = 0.26; p = 0.03), but not SvO₂ (r = 0.07; p = 0.74).

Conclusion: In this secondary analysis, RrSO₂ was consistently lower than blood gas O₂ saturations and correlated with SaO₂ and ScO₂ but not SvO₂. Lack of a correlation to SvO₂ could be due to the small UVC sample size limiting statistical power. Future studies should prospectively evaluate if RrSO₂ truly primarily reflects venous oxygenation in preterm neonates.

Key points: · Renal oxygenation correlates with arterial and capillary oxygen saturation.. · Renal oxygenation did not correlate with venous oxygenation from umbilical venous catheters.. · Studies are needed to determine if renal oxygenation primarily reflects venous or arterial oxygen..