SULFOBROMOPHTHALEIN SODIUM EXCRETION TEST AS A MEASURE OF LIVER FUNCTION IN PREMATURE INFANTS

Abstract

In normal adults, following a single intravenous injection of BSP, the logarithmic decline of plasma BSP levels is rectilinear. In patients with hepatic disease, the plotted values are curvilinear with flattening of the curve, or "saturation," occurring at high plasma BSP concentration. The use of the excretion curve provides a dynamic representation of the hepatic uptake of dye throughout the test, avoids the theoretic objections to the 45 minute test, and obviates the necessity for plasma volume determinations. Thirty-five healthy prematures of varying age and weight were the subjects of a study of liver function by the bromsulphalein excretion test. As measured by the BSP excretion test, there is progressive maturation of liver function with age in prematures which does not necessarily correlate with weight. The excretion curves obtained in prematures 18 to 28 hours of age resemble those of older patients with severely impaired hepatic function. Clearance of dye in these subjects is slow throughout the test. With increasing age there is a gradual change in the pattern of the curves characterized by the appearance of the initial sharp slopes coincident with rapid dye removal. "Saturation," or flattening of the curves, persists until a later age and takes place at progressively lower plasma levels. This biphasic pattern is apparent in the prematures over 4 days of age. The normal adult pattern is not attained until about 6 to 8 weeks although the 45 minute retention values become normal at three weeks. The gradual development of normal excretion curves in premature infants may be explained by the progressive maturation of the anatomic and physiologic factors involved in the mechanism of BSP clearance. The increasing size of the capillary network in the liver that occurs with advancing age in effect increases hepatic blood flow and exposes a greater volume of blood in the sinusoids to the activity of the liver. The appearance of the initial sharp slopes, representing rapid dye removal, probably results from this increasing vascularity and possibly from maturation of the hepatic uptake mechanism. The continuance of the biphasic character of the curves probably results from inability to excrete the dye efficiently into bile.