A 65-year-old man with mild hea failure is treated with a loop diuretic. A few days later the man complains of muscle weakness. Laboratory results are shown below. Aerial PCO2: 48 mm Hg Aerial pH: 7.49 Plasma HCO3-: 35 mEq/L Which of the following is most likely decreased in this man?
The lab repos indicate that the man has developed metabolic alkalosis (increased PCO2, pH, and HCO3-), which occurs commonly with overuse of diuretics (thiazides and loop diuretics). The overuse of a loop diuretic increases the excretion of sodium and potassium by the kidneys. The increase in potassium excretion leads to a decrease in plasma potassium levels. The sodium depletion stimulates renin secretion, which in turn raises angiotensin II levels in the plasma (which also stimulates aldosterone secretion).
Plasma angiotensin
Plasma potassium
Potassium excretion
Renin secretion