Urinary beta-2-microglobulin excretion in prematures with respiratory distress syndrome

Urinary concentrations of beta 2-microglobulin (beta 2M) were studied in 25 prematures (less than or equal to 35 weeks) with respiratory distress syndrome (RDS), divided into two groups (group 1: ventilation greater than or equal to 2 days; group 2: oxygenotherapy less than or equal to 4 days), to assess the value of beta 2M in the detection of tubular damage in relation to the severity and management of the respiratory disease. The data were compared with those obtained from 10 healthy controls, matched for birth weight and gestational age. Measurements of beta 2M were made on urine collected on days 1, 3, and 5 until the recovery phase of RDS was reached. Urinary beta 2M values for infants with RDS were increased on days 1 and 3, with respect to the controls, and significantly increased in the ventilated group (8,814 +/- 4,768 vs. 2,594 +/- 3,231 micrograms/l, p less than 0.005 and 7,624 +/- 6,264 vs. 2,762 +/- 2,316 micrograms/l, p less than 0.05, respectively). Serum sodium and creatinine, creatinine clearance, fractional tubular sodium excretion and renal function index on day 1 were similar in prematures with or without RDS. However, the ventilated newborns presented higher urinary sodium excretions. On the 5th day, no significant differences in urinary beta 2M were found among the groups. The elevated levels of urinary beta 2M in the acute phase of RDS and in the more severe lung disease indicate the existence of subclinical tubular dysfunction, probably secondary to hypoxic stress and to negative hemodynamic effects of ventilatory management.