Electrolyte disorders associated with respiratory distress syndrome and bronchopulmonary dysplasia.

In understanding the various electrolyte disorders associated with respiratory failure, one has to appreciate how the otherwise healthy premature infant maintains extracellular fluid homeostasis. The same physiologic processes that regulate body fluids are affected to varying degrees in the infant with respiratory failure. Maintenance of sodium conservation by the kidney is of critical importance for survival and growth. The immature kidney tends to exhibit excessive sodium wasting especially early on, but appropriate positive sodium balance is achieved generally within the first week. Appropriate reduction in extracellular fluid occurring during the first week or so of life is expected and if it is not allowed to occur may result in dilutional hyponatremia and an increase in pulmonary interstitial water. Diuretics, when used to promote an increase in lung compliance, can themselves generate significant morbidity. Sodium depletion, hypokalemia, alkalosis, and calcium wasting all can either be caused by or exaggerated by the loop diuretics. Thus, one must consider the maturational state of the infant, the infant's response to pulmonary failure, and iatrogenic factors influencing the outcome.