Dexamethasone does not affect vasopressin release in bronchopulmonary dysplasia

Elevated levels of vasopressin (AVP) have been found in premature infants w ith bronchopulmonary dysplasia (BPD), and may be related to abnormalities o f water handling, and to non-pulmonary signs of edema. Dexamethasone treatm ent improves pulmonary function in infants with BPD, and is frequently asso ciated with a significant increase in diuresis and a decrease in weight gai n. To determine whether this diuresis is primarily the result of AVP inhibi tion (potentially induced by steroid treatment), we measured endogenous AVP levels in nine premature babies with BPD [birth weight 802+/-141 (SD) g; g estation 26+/-2 weeks, age 26+/-17 days], before initiation, and 3 and 7 da ys after the start of dexamethasone therapy (0.5 mg/kg/day). All study infa nts required mechanical ventilation, and none was receiving diuretics or ca rdiac inotropes during the study. Results indicated that premature infants with BPD have functionally unmodified AVP levels after 3 and 7 days of dexa methasone therapy (pre-dexamethasone 5.9+/-2.1 ng/l vs post-dexamethasone 7 .0+/-3.0 and 8.0+/-1.9 ng/l at 3 and 7 days, respectively). Pulmonary funct ion improved with oxygenation indexes decreasing (pre-dexamethasone 14+/-7 vs post-dexamethasone 9+/-7 and 7+/-3 at 3 and 7 days, respectively). A con current reduction in weight gain occurred (pre-dexamethasone 12+/-10 g/kg/d ay vs post- dexamethasone 7+/-3 g/kg/day and 3+/-1.5 g/kg/day on days 3 and 7, respectively). These data suggest that the improvement in lung function with dexamethasone treatment for BPD in premature infants does not correla te with a diuresis that results from vasopressin inhibition, and potentiall y induced by dexamethasone.