Instillation rate effects of Exosurf on cerebral and cardiovascular haemodynamics in preterm neonates

The acute effects of surfactant instillation rate on the cerebral and cardiovascular haemodynamics were studied in a randomised trial of 27 preterm neonates with respiratory distress syndrome (RDS). Cerebral blood flow velocity (CBFV), mean arterial blood pressure (MABP), blood gases and electroencephalogram (EEG) were continuously recorded before, during, and for at least 10 minutes after the administration of surfactant. The measurements were repeated one, three, and six hours later. Left ventricular output (LVO) and ductal patency were assessed 10 minutes before and then one, three, and six hours after surfactant administration. Surfactant (Exosurf) was instilled rapidly over five minutes in 13 infants and slowly over 15 minutes in 14 infants. The rapid group showed a significant but transient increase (mean 38%) in CBFV, a rise strongly related to an increase in carbon dioxide tension. No significant change in CBFV was observed in the slow group. There were no significant changes in EEG, MABP, LVO, or ductal shunting in either group. The findings suggest that rapid instillation of Exosurf leads to an increase in CBFV and partial carbon dioxide pressure (PCO2) and requires a close monitoring of blood gases to maintain adequate ventilation. Furthermore, the findings should alert clinicians to the need for slow infusion of Exosurf.