Dexamethasone treatment and fluid balance in preterm infants at risk for chronic lung disease

The influence of dexamethasone on diuresis in preterm infants has not been well studied. We examined 15 preterm infants at risk for chronic lung disea se with gestational ages ranging from 26 to 29 wk (median 27.6 wk) and birt hweights ranging from 700 to 1485 g (median 965 g). Urine output, blood glu cose, serum urea, serum creatinine, serum sodium and serum potassium, as we ll as systolic, diastolic and mean arterial pressure were measured on the d ay before, and on 4 consecutive days after starting treatment with dexameth asone (0.25 mg kg(-1) i.v., twice daily). We found an increase of diuresis of 30 mi kg(-1) d(-1), 48-96 h after starting dexamethasone treatment. This coincided with a gradual but significant increase of serum urea levels and arterial pressure. During the study period, fluid and protein intake remai ned constant. Blood glucose and serum creatinine levels did not change. Our findings suggest that the increased urine output following dexamethasone t reatment might be caused by two factors: (1) pressure diuresis induced by t he increase of arterial pressure and (2) an increase of the osmolar load to the kidney due to an increase of serum urea. Conclusions: This study demonstrates that a significant increase of diuresi s occurs in preterm infants, 48-96 h after starting dexamethasone. A carefu l monitoring of fluid balance during the first days of dexamethasone treatm ent is recommended.