The role of serum and urinary urea in the evaluation of enteral protein intake in adequate and small-for-gestational-age very low birth weight infants.
OBJECTIVE
Very low birth weight (VLBW) infants have special nutritional needs. There is a current tendency to individualize their protein needs. The objective of this study was to determine the suitability of serum and urinary urea as indicators for protein intake in adequate-for-gestational-age (AGA) and small-for-gestational-age (SGA) VLBW infants.


METHODS
Prospective study in the nursery attached to the Maternity Ward of the "Prof. Pedro de Alcântara" Children's Institute, Hospital das Clínicas, Department of Pediatrics, Faculdade de Medicina da Universidade de São Paulo, Brazil.


METHODS
Seventy-two VLBW infants (mean protein intake = 3.7 mg/kg/day) were enrolled in a prospective cohort study in two groups: AGA (n = 34) and SGA (n = 38). Blood samples, six-hour urine (6hUr) collections and urine sample tests (STUr) were obtained for urea and creatinine assays at three and five weeks of life.


METHODS
Student's t test, Pearson correlation and linear regression (p < 0.05).


RESULTS
There were no differences between groups for serum urea, 6hUr and STUr, or between two assessments within each group. Serum urea correlated with 6hUr in both AGA and SGA, and to STUr in SGA; 6hUr correlated with STUr in both AGA and SGA. There was no correlation between protein intake and serum or urine urea.


CONCLUSIONS
Serum and urinary urea did not reflect protein intake when mean intakes of 3.7 g/kg/day were used. Sample tests of urinary urea can be as reliable as urea from urine collected over longer periods.
Darcie
Silvana
S
Prof. Pedro de Alcântara Children's Institute, Hospital das Clínicas, Department of Pediatrics, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil. sdarcie@uol.com.br
Leone
Cléa Rodrigues
CR
D015415:Biomarkers / Q000097:blood / Q000652:urine; D003404:Creatinine / Q000097:blood / Q000652:urine; D004044:Dietary Proteins / Q000008:administration & dosage / Q000378:metabolism*; D002149:Energy Intake / Q000502:physiology*; D004812:Epidemiologic Methods; D005260:Female; D005865:Gestational Age; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D007236:Infant, Small for Gestational Age / Q000097:blood / Q000378:metabolism* / Q000652:urine; D019102:Infant, Very Low Birth Weight / Q000097:blood / Q000378:metabolism* / Q000652:urine; D008297:Male; D014508:Urea / Q000032:analysis* / Q000097:blood / Q000652:urine
D015415:Biomarkers; D004044:Dietary Proteins; D014508:Urea; D003404:Creatinine