Urinary Nitrogen Constituents in the Postsurgical Preterm Neonate Receiving Parenteral Nutrition

Abstract

Minimal information is available defining urinary nitrogen constituents in preterm neonates receiving parenteral nutrition (PN). The study objective was to evaluate 24-hour urine collections for total urinary nitrogen (TUN), urinary urea nitrogen (UUN), and the nitrogen content in creatinine, ammonia, free amino acids, protein, hippuric acid, and uric acid at baseline (days 1 to 2 of PN and days 1 to 3 after surgery) and 7 days later in eight preterm, postsurgical neonates. Calculation of undetermined nitrogen was also completed. Comparisons with historic, normal data were made for each urinary nitrogen constituent. At baseline, PN provided 59 +/- 10 nonprotein kcal/kg.day-1 and 430 +/- 54 mg/kg.day-1. At day 7, PN provided 106 +/- 23 nonprotein kcal/kg.day-1 and 432 +/- 30 mg/kg.day-1. TUN, UUN, and protein nitrogen decreased significantly from baseline at day 7 (p < .05). The percentages of TUN as amino acids, creatinine, and uric acid nitrogen were calculated. Percent amino acid nitrogen (6.0 +/- 2.3% vs 8.4 +/- 1.5%, p < .05), percent creatinine nitrogen (1.6 +/- 0.5% vs 2.9 +/- 0.8%, p < .001) and percent uric acid nitrogen (1.7 +/- 0.9% vs 3.6 +/- 2.1%, p < .05) increased significantly at day 7. The observed urinary free amino acid nitrogen fraction represented a higher percentage of TUN both at baseline and at day 7 when compared with term neonatal reference data, whereas creatinine nitrogen, uric acid nitrogen, and protein nitrogen represented a lower percentage of TUN. However, amino acid and creatinine nitrogen as a percentage of TUN were similar to levels in milk formula-fed preterm infants.(ABSTRACT TRUNCATED AT 250 WORDS)

Sodium citrate supplementation in inborn argininosuccinate lyase deficiency: A study in a 5-year-old patient under total parenteral nutrition

“…In contrast to earlier reports [4], where 15%-20% of urinary nitrogen remained undefined, on the first 2 days of our study nearly the whole amount of urinary nitrogen could be explained by the metabolites measured (Fig2). As the patient became gradually alkalotic (r --0.99) the amount of urinary nitrogen that we could not explain chemically, rose significantly to finally 65.9% of total urinary nitrogen.…”

“…Amino acid analysis in blood and urine was done with standard methods [4,15] using an amino acid analyser (Liquimat 4, Labotron); the concentrations of argininosuccinate and its anhydrides were approximated with the calculating factor for norleucine. In finally judging changes in renal total nitrogen disposal, further approximation was done by equating the calculated total excretion of argininosuccinate and its anhydrides with the amount of chemically undefined urinary nitrogen on day 1 (Fig.…”

Clinical relevancy of nonurinary nitrogen excretion in newborns and infants after digestive tract surgery

“…Moreover, we found a small but significant influence of both SSS and PRISM on total nitrogen excretion. Our findings are in keeping with those of Chaloupecky et al 3 and Helms et al 8 and with the notion that nitrogen excretion in infants, as in older children and adults, is proportional to the stress of surgery and to the stress imposed by the underlying disease, 1,[17][18][19] indicating that our findings are valid. The limitations of the scoring systems should, however, be noted.…”

Assessing the Validity of Adjusted Urinary Urea Nitrogen as an Estimate of Total Urinary Nitrogen in Three Pediatric Populations

“…Between 4.6% and 7.5% of TUN is nitrogen from ammonia in TPN-fed neonates and infants. 16 Additionally, in pediatric patients and during metabolic stress, ammonia excretion is higher than in normal adults, which can lead to an increased error in UUN measurement if uncorrected for nitrogen from preformed ammonia.…”