Cerebral Blood Flow Velocity Changes after Bovine Natural Surfactant Instillation

OBJECTIVE: To determine the effects of bovine natural surfactant (beractant) instillation on cerebral hemodynamics in preterm infants with respiratory distress syndrome (RDS). STUDY DESIGN: Preterm infants who required surfactant for RDS were enrolled. Cerebral blood flow velocity (CBFV) waveforms from the pericallosal artery were analyzed by pulsed Doppler ultrasonography with the anterior fontanel serving as an acoustic window. CBFV was measured before and at 5, 10, 20, and 30 minutes after the first dose of a bolus instillation of surfactant in four aliquots. Simultaneously with CBFV measurements, mean blood pressure (MBP), heart rate, and ventilator settings were recorded. pH, PACO2, and PAO2 before and at 30 minutes after surfactant administration were also determined. RESULTS: The 30 enrolled preterm infants had a mean birth weight of 973 gm (513 to 1996 gm) and a mean gestational age of 27 weeks (23 to 33 weeks). Mean postnatal age at surfactant administration was 4.7 ± 2.7 hours. There were no significant changes in pH and PACO2 before and at 30 minutes after surfactant (before surfactant: mean pH of 7.29 ± 0.07 and mean PACO2 of 44.4 ± 7.1 torr; after surfactant: mean pH of 7.31 ± 0.07 and mean PACO2 of 42.7 ± 8.3 torr). PAO2 increased significantly from a pre-surfactant mean of 83 torr to 130 torr at 30 minutes after surfactant (p < 0.05), with no significant changes in mean airway pressure. There were no significant changes in MBP, heart rate, mean CBFV, peak systolic flow velocity, and diastolic flow velocity before and after surfactant instillation regardless of gestational age. Individual changes in mean CBFV were related to MBP changes (p < 0.001, linear mixed models with random effects). CONCLUSION: In low birth weight infants with RDS, bovine surfactant instillation is not associated with a significant alteration in cerebral hemodynamics. However, the direct relationship between CBFV and MBP is consistent with the reported pressure-passive cerebral circulation in sick preterm infants.