Relationship Between Silent Hypoxemia and Blood Gas Parameters (p50, ctO<sub>2</sub>, and Lactate Levels) in Neonates Born with MSAF

Background: The association of meconium-stained amniotic fluid (MSAF) with neonatal respiratory distress poses a significant clinical challenge. The increased risk of hypoxemia, which is often undetected by traditional markers, further complicates this issue. Subclinical oxygenation deficiencies, also called “silent hypoxemia,” require advanced monitoring methods to ensure timely intervention. Objectives: The aim was to investigate the association between silent hypoxemia and blood gas parameters such as P50, oxygen content (ctO2), and lactate levels in neonates with MSAF. Methods: A prospective observational study was conducted on 183 neonates (68 with MSAF and 115 controls) born at full term. This study was conducted at Bağcılar Training and Research Hospital, Türkiye, from December 1, 2023, to June 1, 2024. The study included full-term neonates (37 - 42 weeks) born with MSAF or clear amniotic fluid. Exclusion criteria included congenital anomalies, preeclampsia, multiple gestation, and maternal substance use. Umbilical cord blood gas analysis measured pH, lactate, oxygen content (ctO2), and P50. Demographic and clinical data were recorded. Statistical analyses assessed group differences and correlations between P50 and blood gas parameters. Results: P50 and lactate levels were significantly higher in the MSAF group compared to controls (P50: 24.65 ± 3.52 vs. 23.54 ± 3.37, P = 0.036; lactate: 2.81 vs. 2.30 mmol/L, P = 0.003). In contrast, ctO2 was lower in the MSAF group (11.9 vs. 13.1 mmol/L, P = 0.035). P50 was positively correlated with lactate (r = 0.39, P = 0.001) and negatively correlated with ctO2 (r = -0.54, P < 0.001), pH and SO₂. Our findings showed a distinct pattern of silent hypoxemia between MSAF neonates and controls. Conclusions: Our study results highlight that subclinical oxygenation monitoring protocols, including P50 in neonates with MSAF, may be clinically useful. Further research is needed to integrate these findings into clinical practice.