Nucleated Red Blood Cells as Markers of Perinatal Adaptation in Preterm Neonates Receiving Minimally Invasive Surfactant Therapy

Objective The study aimed to assess the association of nucleated red blood cells (NRBC), a surrogate of intrauterine hypoxia, and elevated pulmonic vascular resistance (E-PVR) and oxygen requirement after minimally invasive surfactant therapy (MIST). Study Design Retrospective study of a cohort of preterm neonates that received MIST in a single unit. Results NRBC were measured in 65 of 75 (87%) neonates administered MIST during the period. In total, 22 of 65 (34%) infants had pre-MIST echocardiography (ECHO). Neonates with elevated NRBC (predefined as >5 × 10 9 /L, n = 16) required higher post-MIST fraction of inspired oxygen (FiO 2) than neonates with normal NRBC (<1 × 10 9 /L, n = 17; FiO 2 = 0.31 ± 0.10 and 0.24 ± 0.04, respectively, p = 0.02). NRBC correlated positively with % of time in right to left ductal shunt (r = 0.51, p = 0.052) and inversely with right ventricular stroke volume (r = -0.55, p = 0.031) and time to peak velocity to right ventricular ejection time ratio (r = -0.62, p < 0.001). Conclusion Elevated NRBC are associated with elevated FiO 2 after MIST and elevated E-PVR. Intrauterine hypoxia may impact postnatal circulatory adaptations and oxygen requirement. Key Points Post-MIST FiO2 requirements are significantly higher in infants with elevated NRBC. NRBC correlates positively with elevated PVR in neonates requiring. Intrauterine hypoxia may play a role in postnatal circulatory adaptations in neonates with RDS.