Evans, Nicholas John (1985) Skin permeability in the newborn. University of Southampton, Doctoral Thesis.
Abstract
High skin permeability causes clinical problems for preterm infants by allowing high transepidermal water losses and percutaneous absorption of topically applied substances with toxic systemic effects. The potential use of this high skin permeability to administer drugs and oxygen to preterm infants was explored. Theophylline was administered percutaneously to 25 preterm infants by applying a theophylline gel to the skin. Therapeutic serum levels were maintained or increased in all the infants, though the older infants absorbed less of the drug. This mode of drug administration is feasible and has potential advantages over other methods. Newborn percutaneous gas exchange was studied using a new method, validated by studying adult skin. Gas exchange is related to gestation with infants of less than 31 weeks having much higher rates than term infants. A very preterm infant surrounded by 40% oxygen could absorb 13% of total resting oxygen requirements through the skin. Percutaneous oxygen might be a way of supplementing oxygen delivery to sick immature infants. The structural basis of the changes in skin permeability influencing drug absorption and gas exchange was examined with postmortem skin histology. The epidermis increases in thickness with gestation, by 34 weeks it is largely mature. There is rapid thickening of the epidermis and stratum corneum after birth in preterm infants, by two weeks of age both are structurally similar to that of term infants. There is a close correlation between structure and function in newborn skin. Urinary excretion of epidermal factor (EGF) was examined to see if it might be responsible for this rapid epidermal maturation. There is no change in EGF excretion during the period of rapid postnatal maturation of the skin. EGF excretion increases with postconceptional age, birth is an incidental event. (D72153/87)
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