OBJECTIVE

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

STUDY DESIGN

A secondary analysis of a prospective RrSO monitoring study in preterm neonates born <32 weeks gestational age. Neonates with any blood gas obtained during RrSO monitoring were included. RrSO was compared with simultaneous O 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. RrSO was lower than the median SvO (58.8 vs. 78.9, <0.01), SaO (51.0 vs. 93.2, <0.01), and ScO (62.2 vs. 94.25, <0.01). RrSO values correlated to both SaO and ScO ( = 0.32; <0.01,  = 0.26;  = 0.03), but not SvO ( = 0.07;  = 0.74).

CONCLUSION

In this secondary analysis, RrSO was consistently lower than blood gas O saturations and correlated with SaO and ScO but not SvO. Lack of a correlation to SvO could be due to the small UVC sample size limiting statistical power. Future studies should prospectively evaluate if RrSO 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..