Current advances in perinatal medicine.

The enhancement of pulmonary maturation with the resultant ability to prevent hyaline membrane disease has given rise to the use of a number of drugs experimentally including corticosteroids, thyroxine, aminophylline, heroin, and several suggested others for this purpose. In clinical use to date only the corticosteroids have been widely utilized in man but it is clear that these agents are capable of effecting an advancement in the maturation of the surfactant system of the lung and a subsequent reduction in the incidence of severity of hyaline membrane disease. However, all agents which act by the enhancement of maturation also carry with them a resultant arrest to replication of tissues and there have been demonstrable effects on both the lung and possibly the brain of the organisms to whom these agents have been administreted. In this connection it is, therefore, important to realize that the advantages gained from these agents may be counterbalanced by disadvantages from their usage and that a reasoned and careful approach in each individual case is mandatory when use of such agents is considered. Experimental and clinical studies suggest the possibility that Vitamin E acting as a free radical scavenger may be important in the prevention of oxygen toxicity both to the eye (retrolental fibroplasia) as well as ameliorating the oxygen component of the destructive effects of respirator lung disease (bronchopulmonary dysplasia). The action of Vitamin E under these circumstances is not dependent upon its actual quantitative level in the plasma of premature infants but in utilization to its excess. Although phototherapy has been universally and widely used since 1958, precise studies of its mechanism of action have not been revealing. Recent work has suggested that following exposure to photoirradiation, bilirubin in its unconjugated form can be seen to appear in the excretory bile ducts suggesting the transport of unconjugated bilirubin through the liver. More recent evidence has also suggested that this occurrence is the result of internal rotation following light exposure of one of the double bonded rings which effectively converts the molecule from a lipid soluble to a water soluble and thereby excretable form. These studies would not only account for an appropriate explanation of the quantitative reduction in bilirubin observed but carry with them the other important consideration that the amount of light exposure necessary to accomplish this is strikingly less than the previously considered photooxidation reaction. The clinical implications of these findings may suggest a reevaluation of the quanta of light which has been used for purposes of phototherapy to date.