Surfactant therapy: new questions arise.

Surfactant therapy: New questions arise

In the final weeks before birth, a human fetus makes a variety of preparations for life outside the womb. Among these last arrangements is the production of surfactants inside the lungs. These soap-like compounds help break surface tension along the inner linings of the lungs, ensuring the delicate membranes will inflate and not stick together with the first breaths of air.

Infants born several weeks early, or those who for some other reason have yet to begin producing sufficient quantities of surfactants, are at risk of dying from respiratory distress syndrome in their first days of life. Several studies in the past four years have demonstrated increased survival rates when these high-risk infants are given an experimental treatment in which a surfactant is "blown" into their lungs immediately after birth. But the therapy has not gained Food and Drug Administration (FDA) approval, in part because few data exist about its long-term effects.

A new study described in the October PEDIATRICS provides one of the few looks so far at the cognitive and neurological development of surfactant-treated children. The results are not critical of the treatment, but fall short of encouraging--and may have the FDA demanding more safety studies.

Michael S. Dunn and his colleagues at the Women's College Hospital in Toronto performed a blinded, two-year follow-up study of children born at gestational age 30 weeks or less--including 30 children who had received surfactant therapy at birth and 25 controls who had not. The children were checked for neurological handicaps by a variety of measures, including the Bayley Scale of Infant Development, which assesses cognitive development.

"The rate of major neurodevelopmental handicap in the surfactant group is noticeably higher than that in either the control group or the nursery population in general," the researchers report, noting five children with major handicaps in the surfactant group compared with two in the control group. "These differences are nto statistically significant because of the small numbers," they add, "but the trend is disturbing."

Major handicap was defined in part by a Bayley score of less than 50--the type of score that would be expected from a functionally very limited 4-year-old with the cognitive development of a 2-year-old. Dunn believes the disconcerting trend is probably due to chance alone, but "is of sufficient concern that we should keep looking at it."

The study, which used surfactant purified from cow lungs, follows two other recent reports that showed no differences in development problems in surfactant-treated and untreated survivors of premature birth.

"The real critical question is whether the use of surfactant is increasing the survival of babies who are destined to be handicapped," says Allen Merritt of the University of California, San Diego, who recently coauthored a follow-up study of 61 surfactant-treated babies. Moreover, he adds, "one critical question that remains to be answered is whether some surfactants are better than others."

The San Diego team--now in the midst of a 200-infant clinical trial -- is using human surfactant, which lacks the traces of bovine proteins that some researchers theorize may make bovine surfactants less than ideal. But human surfactant "is more difficult to obtain and process and produce, so its possibility for widespread distribution is less," Merritt notes. Other researchers are experimenting with synthetic surfactants.

Preliminary studies reported by Dunn and his colleagues suggest that no allergic or other immunological ill effects resulted from the bovine proteins in their surfactant.

If further tests indicate increased survival of severely handicapped children following surfactant treatment, Dunn says, neonatologists will be faced with "an ethical can of worms, in which we have to deal with our feelings about the value of a handicapped life. There's a definite quality-of-life question."