Glomerular filtration in low birthweight neonates

: The glomerular filtration rate (GFR) was estimated in mature newborns appropriate for gestational age (AGA), mature newborns small for gestational age (SGA) and premature newborns AGA on the 2nd day and the end of the 3rd week of life. The GFR was determined by mannitol using the slope-clearance technique. On the 2nd day the GFR is significantly diminished in mature newborns SGA (1.21 ml/kg X min) compared to mature newborns AGA (1.84 ml/kg X min) as well as premature newborns AGA (1.54 ml/kg X min). During the first 3 weeks of life the GFR increases significantly in mature newborns both AGA (2.20 ml/kg X min) and SGA (1.65 ml per kg X min), whereas the increase is insignificant in premature newborns AGA (1.70 ml per kg X min). Therefore there is no difference between mature newborns SGA and premature newborns AGA at the end of the 3rd week of life. The decreased GFR of newborns SGA during the first weeks of life has to take into consideration for dosage of drugs tending to cumulate and for composition of parenteral nutrition.