Kaluresis and diuresis after administration of antidiuretic hormone to hyperkalemic dogs.

Dogs infused with 2 meq KCl/kg per h exhibit electrocardiographic evidence of prelethal cardiotoxicity in about 3 h when serum potassium reaches a level between 10.2-10.5 meq/liter. During this time, their urine output of 30 ml/h is equal to the volume of KCl infused. Studies of the potassium distribution in these animals indicate that 20 percent of the infused ion is added to the extracellular fluid and red blood cell mass, 20 percent is excreted in the urine, while the remaining 60 percent is unaccounted for and presumably transferred to intracellular fluid. Dogs treated with moderately large doses of antidiuretic hormone intramuscularly before and during KCl infusion delay development of prelethal cardiotoxicity for about 5 h, with serum potassium levels comparable to those of untreated dogs. In addition, treated animals display a considerable diuresis and kaluresis with urine volumes nearly 4 times that of the volume infused. The potassium ion distribution in animals given antidiuretic hormone is much different from that of untreated dogs, with 55 percent of the infused ion found in the urine, about 15 percent in extracellular fluid and red blood cell mass, and only 30 percent presumably transferred to intracellular fluid. Transfer of potassium to intracellular fluid was calculated to be 3.1 plus or minus 0.7 meq/kg in antidiuretic-hormone-treated animals and 3.8 plus or minus 0.7 meq/kg in untreated (control) animals. Since these values are, within experimental error, quite comparable, it is possible that antidiuretic-hormone-induced kaluresis and diuresis are involved in protecting some animals from the effects of hyperkalemia by delaying the attainment of cardiotoxic blood levels.