March 1981 462 TheJournalofPEDIATRICS The diuretic phase of respiratory distress syndrome and its relationship to oxygenation To determine the relationship between improvement in pulmonary function and diuresis in respiratory distress syndrome, ten consecutive premature infants requiring mechanical ventilation for severe RDS were studied. Every infant had a diuresis (output~intake > 80%), which began at 26 to 34 hours of life and which lasted for an additional 64-72 hours. The diuresis preceded significant improvement in AaD% and ventilator settings (IMV, PIP, PEEP) by 52 hours. There was a significant decrease in body weight among all study infants during the first four days of life despite an increase in fluid intake. This study suggests a relationship in RDS between improvement in oxygenation and removal of interstitial lung edema. Craig B. Langman, M.D.,* William D. Engle, M.D., Stephen Baumgart, M.D., William W. Fox, M.D., and Richard A. Polin, M.D., Philadelphia, Pa. IMPAIRED PULMONARY FLUID DYNAMICS are known to have a role in the pathophysiology of respirato- ry distress syndrome. Although the influence of lung water on the severity of RDS is not completely under- stood, past studies have demonstrated the presence of increased lung water content, dilated lymphatics, and interstitial pulmonary edema?' 2 The accumulation of pulmonary interstitial water may result in narrowing of terminal airways and impaired gas exchange? Normal infants have a diuresis and weight loss during the first three days of life. 4-6 However, two studies in infants with respiratory distress syndrome and severe hypoxemia have reported a reduced urine output in the first three days of life when compared with controls. 7. s During the recovery phase of RDS many of these infants had an increase in urine output. These studies suggested that improvement in pulmonary function occurred prior to the increase in urine output. In contrast, clinical observations in our nursery suggested that the increase in From the Divisions of Neonatology and Nephrology of The Children's Hospital of Philadelphia and the Department of Pediatrics of the University of Pennsylvania School of Medicine. *Reprint address: Division of Nephrology, The Children"s Hospital of Philadelphia, 34th St. & Civic Center Blvd., Philadelphia, PA 19104. urine output precedes the recovery of pulmonary function in infants mechanically ventilated for RDS. 9 The purpose of this study was to confirm the occurrence and magnitude of diuresis in RDS and to investigate the temporal relationship between spontaneous diuresis and See related article, p. 476. Abbreviations used RDS: AaD%: IMV: PIP: PEEP: I: O: FI%: respiratory distress syndrome alveolar-arterial oxygen gradient intermittent mandatory ventilation peak inflating pressure positive end expiratory pressure intake output concentration of inspired oxygen improvement in respiratory status in the clinical course of infants mechanically ventilated for respiratory distress syndrome. METHODS Ten consecutive premature neonates (mean birth weight 1,920 gm, mean gestational age 33 weeks) with moderate-to-severe respiratory distress syndrome and res- piratory failure were studied (Table). Diagnosis was Vol. 98, No. 3, pp. 462-466 0022-3476/81/030462+05500.50/0 9 1981 The C. V. Mosby Co.