[Effects of diuretic therapy on electrolyte and acid-base homeostasis]

The use of diuretics leads to a negative sodium and fluid balance without primary effects on serum sodium concentration. This parameter is regulated by the activity of the antidiuretic hormone (ADH) system. Secondary changes in other electrolyte systems and in acid base homeostasis also are induced by diuretic therapy. Especially diuretic induced hypokalemia is important as it is responsible for the excess mortality observed in patients with diuretic treated essential hypertension and cardiac abnormalities. All adverse metabolic effects of diuretic therapy are, in contrast to the antihypertensive action, dose dependent. Changes in fluid and electrolyte metabolism induced by diuretics occur within the first 2 or 3 weeks after initiation of medication. Counterregulatory mechanisms are activated and a new steady state is established. Serial laboratory determinations after this period are not necessary as long as this steady state is not affected by additional events (like a change in therapy or diet as well as the occurrence of vomiting or diarrhea).