Comparison of the changes in the a/A oxygen ratio after administration of two surfactants for the treatment of neonatal respiratory distress syndrome.

ABSTRACT

The aim of this study was to compare the acute changes in a/A O2 ratio after administration of two surfactants, Survanta (Ross Laboratories), and Exosurf Neonatal (Glaxo Wellcome Co.) in prematures with respiratory distress syndrome. Twenty-seven premature infants weighing 1030 + 1680 g with respiratory distress syndrome were ventilated and randomly assigned to receive two doses of either Survanta (n = 15) or Exosurf (n = 12) when a/A O2 ratio was < 0.22. The assigned surfactant was prepared and administered in accordance with the manufacturer's instructions. a/A O2 ratio was measured before each dose and 2 and 6 h later. The percentage change of the ratio from the first measurement has been calculated. There was no significant difference between the two groups as regard to birth weight, gestational age, Apgar Score, and a/A O2 ratio before administration of the drug. However, the age at commencement of treatment was significantly lower in Survanta group. The mean of changes in a/A O2 ratio was significantly higher in Survanta than in Exosurf on all occasions (P < 0.05). There was no correlation between the initial improvement in the ratio and the age of administration of the first dose of the drugs. The initial improvement in a/A O2 ratio after Survanta may be explained by either smaller volume of the drug (4 ml/kg) compared to Exosurf (5 ml/kg) or better spreading properties of the drug. Earlier administration of the second dose of Exosurf may accelerate the response to the drug.