A bridge over troubled water...mixed water and electrolyte disorders

Plasma volume, nitrogenous wastes in the plasma, and plasma osmolality profoundly affect the function of various organs in the body, particularly the central nervous system and the heart. Some parameters are more critical for these organs than others, so that, when homeostatic mechanisms come into play, the body often defends the parameter of greatest importance at the expense of others. The hyponatremia and azotemia that develop in dehydrated infants exemplify this prioritization of the body. The primary goal of therapeutic intervention in such circumstances is, therefore, geared toward a correction of dehydration. While alterations in plasma and urinary electrolyte patterns commonly reflect adjustments made by the body's machinery, it is essential at the bedside to identify factitiously abnormal laboratory results produced by laboratory analytical machines. They measure not only biologically active but also insignificant components of plasma electrolytes and osmolality.