Syndrome of inappropriate antidiuretic hormone secretion in neonates with pneumothorax or atelectasis

Nine episodes of the syndrome of inappropriate antidiuretic hormone secretion occurred in five newborn infants following atelectasis or pneumothorax. All infants had pre-existing lung disease and were being treated with positive pressure ventilation. The mean interval between acute atelectasis or pneumothorax and the development of diagnostic hyponatremia, hypo-osmolal serum, hyperosmolal urine, and oliguria was 13.4 hours. Fluid restriction and removal of the triggering event resulted in resolution of the abnormalities within 1.5 to 4 days. Infants who develop atelectasis or pneumothorax should be evaluated for the subsequent occurrence of SIADH; the administration of a water load to them may result in dilutional hyponatremia, for which fluid restriction, not sodium infusion, is the proper therapy.