[Renal disorders in the newborn infant]

Perinatal anoxia, or postnatal hypoxemia, as seen during respiratory distress syndrome, profoundly affects renal function. Hypoxemic neonates present with decreased water excretion, impaired diluting ability, urine acidification, glomerular filtration rate and renal perfusion. Stimulation of the renin-angiotensin system may explain, at least in part, the pathogenesis of the hypoxemia-induced renal changes. The renal defects are reversible upon restoring normoxemia, extracellular fluid volume and cardiac output. The neonatal kidney can also be affected by iatrogenic manipulations. Drugs acting efficiently on several target-organs can profoundly impair renal function. Tolazoline, sometimes used as a pulmonary vasodilator in persistent pulmonary hypertension of the premature infant, can increase renal vascular resistance with consequent renal failure. Indomethacin, a prostaglandin-synthetase inhibitor used to medically close a patent ductus arteriosus, can depress glomerular filtration and water excretion in the newborn infant. Aminoglycosides are widely used in neonatology. They can easily accumulate in neonates whose GFR is low. Their nephrotoxicity may be lower in neonates than in adults, but is certainly not negligible. Experimental studies and a clinical observation have shown that captopril, a competitive inhibitor of the angiotensin-converting enzyme can produce renal damage in the fetus. Recent progress in pharmacology has provided the neonatologist with effective drugs which are of great value in the neonatal ward. They should however always be used with caution if detrimental side-effects are to be avoided.