NET ACID EXCRETION DURING FIRST WEEK OF LIFE

Abstract

Metabolic acidosis occurs frequently in newborns. We have studied 34 preterm and 12 term infants during their first week of life. Twenty preterm infants were nourished with breast milk or SMA (WyethR); the remaining infants received total parenteral nutrition (TPN) - synthetic amino acids or casein hydrolysate solution. Net acid excretion (NAE) for breast milk vs. SMA fed infants was 5.4 ± 0.4 and 7.8 ± 0.6 uEq/min/m2 (mean ± SEM). The corresponding values for the two TPN solutions in preterm infants were significantly higher at 12.5 ± 1.4 and 19.4 ± 3.5 uEq/min/m2. The casein group of infants developed acidosis with depressed plasma bicarbonate 17.4 ± 2 mEq/1. Term infants treated with the TPN solution produced even greater amounts of net acid, 20.6 ± 2.9 for synthetic amino acids and 35 ± 3.7 uEq/min/m2 for casein hydrolysate. Because of the net base generated from milk consumption, milk fed infants are less prone to develop metabolic acidosis. Due to its inherent acidogenic effect, TPN solutions induce acidosis more readily. Preterm infants receiving TPN are therefore required to generate a higher NAE rate compared to the milk fed infants to maintain acid-base balance. With a similar quantity of TPN intake, the term infants produced higher urinary ammonium, thus NAE.