Abstract 1261 Poster Session IV, Tuesday, 5/4 (poster 325)

The surfactant-related influences on cerebral blood flow velocity (CBFV) have been studied by several investigators, resulting in conflicting data. We determined the effects of bovine natural surfactant (Survanta) instillation on cerebral hemodynamics. CBFV wave forms 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 4 aliquots. Simultaneously with CBFV Doppler measurements, mean blood pressure (MBP) from the umbilical artery catheter, heart rate, and ventilator settings were recorded. pH, PaO2, and PaCO2 before and at 30 minutes after surfactant administration were also determined. Preterm infants (n=30) who required surfactant for respiratory distress syndrome were enrolled; mean birth weight of 973 gm (512 - 1996 gm), and mean gestational age of 27 wk (23 - 33 wk). Mean post-natal age at surfactant administration was 4.7 ± 2.7 hours. There were no significant changes in pH and PaCO2 pre- and 30 minutes post-surfactant (pre-surfactant: mean pH = 7.29±0.07 and mean PaCO2 = 44.4±7.1 torr; post-surfactant: mean pH = 7.31±0.07 and mean PaCO2 = 42.7±8.3 torr). PaO2 increased significantly from a pre-surfactant mean of 83 torr to 130 torr at 30 minutes post-surfactant; p< 0.05) with no significant changes in mean airway pressure. Mean CBFV changes were related to MBP changes (p = 0.01, mixed linear models with repeated measurements). There were no significant changes of MBP, heart rate, mean CBFV, peak systolic flow velocity (PSFV), and diastolic flow velocity (DFV) before and after surfactant instillation regardless of gestational age. We conclude that in low birth weight infants, bovine surfactant instillation was not associated with significant alteration in cerebral hemodynamics. However, the direct relationship between CBFV and MBP is consistent with the reported pressure-passive cerebral circulation in ill preterm infants. (Table) Cerebral hemodynamic changes (mean±SD) before and at 5, 10, 20, and 30 minutes after surfactant (Survanta) instillation.

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