The hemodynamic effects of potassium deficiency in the dog

Potassium deficiency for 3 weeks in dogs caused 374 +/- 38 mEq of sodium retention with increase in body weight, plasma volume, and inulin space. Cardiac output increased from 3.7 +/- 0.6 to 5 +/- 0.6 liters/min (P less than 0.02) and systemic vascular resistance decreased from 3,050 +/- 590 to 2,000 +/- 286 dynes/cm per sec2 (P less than 0.05). Plasma renin activity (PRA) increased from 0.4 +/- 0.1 to 17.2 +/- 0.9 ng/ml per hour (P less than 0.01) without change in plasma aldosterone. Angiotensin sensitivity decreased from a rise of 37 +/- 4 mm Hg in mean arterial pressure (MAP) to 10 ng/kg per min before potassium depletion to a rise of 10 +/- 2 mm Hg after hypokalemia. Urinary prostaglandin E (PGE) excretion increased from control values of 1,224 to 1,556 ng/day to 9,352 +/- 3,670 after 21 days of hypokalemia (P less than 0.01). Indomethacin, 150 mg a day for 3 days, decreased urinary PGE to control values as PRA decreased from 17.2 +/- 5.9 to 1.1 +/- .3 ng/ml per hour and angiotensin sensitivity was partially restored. These findings indicate that hypokalemia increased urinary PGE with extracellular fluid volume expansion, decreased sensitivity to angiotensin and increase in PRA.