Renal handling of beta-2-microglobulin in neonates treated with gentamicin.

Increased levels of urinary beta 2-microglobulin (beta 2M) have been used as a marker of proximal tubular dysfunction in human neonates. To assess the value of beta 2M in the detection of early stages of tubular damage caused by gentamicin, renal handling of beta 2M was studied sequentially in 18 gentamicin-treated neonates with idiopathic respiratory distress syndrome (mean birth weight 1,781 g, mean gestational age 33.7 weeks) during the first 7 days of life. These data were compared with those obtained from 10 control infants matched for gestational and postnatal ages. In addition, follow-up studies of renal function were conducted in 14 of 18 study infants 1 week after termination of therapy, on day 14 postpartum. The (+/- SD) fractional tubular excretion of beta 2M (FE beta 2M) tended to decrease significantly in the control infants from 10.3 +/- 1% on day 1 to 6.5 +/- 0.8% on day 7 postpartum (p less than 0.05). In infants treated with gentamicin, the mean FE beta 2M rose from 10.5 +/- 2% on day 1 to 17.1 +/- 1% on day 7 (p less than 0.01), followed by a decrease to 8.2 +/- 0.5% over the next 7 days (p less than 0.001). Compared with the control infants, values for the infants receiving gentamicin were significantly higher on postpartum days 3,5, and 7 (p less than 0.001). No significant differences in serum creatinine, creatinine clearance, or fractional tubular excretion of sodium were observed between the two groups during the study period.(ABSTRACT TRUNCATED AT 250 WORDS)