Uric acid in a single urine sample from neonates with perinatal hypoxia.

In a referral neonatal intensive care unit, PaO2 values of 40 newborn infants were compared with the serum and urinary uric acid levels. The latter was estimated from the first urine obtained after admission. A significant inverse correlation was found between PaO2 and serum uric acid concentration and between PaO2 and urinary uric acid per creatinine ratio, but no correlation was seen between PaO2 and urinary uric acid concentration. The urinary uric acid per creatinine ratio was determined on the 1st, 2nd and 5th days of life in 27 normal prematures, 28 hypoxic prematures, 23 normal full-term infants and 25 hypoxic full-term neonates. Significantly higher values were obtained in both hypoxic groups on the 1st day, and in hypoxic prematures even on the 2nd day. Although creatinine as a reference substance is regarded as unreliable in the neonatal period, if a single urine sample is only available, determination fo the uric acid per creatinine ratio seems to be warranted, since higher values may retrospectively point to hypoxia.