Regional splanchnic oxygen saturation for preterm infants in the first week after birth: reference values.

Background: Near-infrared spectroscopy is used in the assessment of regional splanchnic oxygen saturation (rSO), but solid reference values are scarce. We aimed to establish reference values of rSO for preterm infants during the first week after birth, both crude and modeled based on predictors.

Methods: We included infants with gestational age (GA) <32 weeks and/or birth weight <1200 g. We excluded infants who developed necrotizing enterocolitis or sepsis or who died. In the first week after birth, we determined a daily 2-h mean of rSO to assess its associations with sex, GA, postnatal age (PNA), small-for-gestational age (SGA) status, patent ductus arteriosus, hemoglobin, nutrition, and head circumference at birth and translated those into a prediction model.

Results: We included 220 infants. On day 1, the mean ± SD rSO value was 48.2% ± 16.6. The nadir of rSO was on day 4 (38.7% ± 16.6 smoothed line) to 5 (37.4%±17.3, actual data), after which rSO increased to 44.2% ± 16.6 on day 7. The final model of the reference values of rSO included the following coefficients: rSO = 3.2 - 7.0 × PNA + 0.8 × PNA - 4.0 × SGA + 1.8 × GA.

Conclusions: We established reference values of rSO for preterm infants during the first week after birth. GA, PNA, and SGA affect these values and need to be taken into account.

Impact: Regional splanchnic oxygen saturation is lower in infants with a lower gestational age and in small-for-gestational age infants. Regional splanchnic oxygen saturation decreases with a higher postnatal age until day 4 after birth and then increases until day 7 after birth. Gestational age, postnatal age, and small-for-gestational age status affect regional splanchnic oxygen saturation and need to be taken into account when interpreting regional splanchnic oxygen saturations using NIRS. Reference values for infant regional splanchnic oxygen saturation can be computed with a formula based on these variables, as provided by this study.