Serum sodium and potassium concentrations were not dif- ferent between groups at the time of randomization. As ex- pected, serum sodium increased in the tolvaptan group, while decreasing in the furosemide group, and the intergroup differences in median change being statistically significant at 48, 72, and 96 h. Changes in serum potassium and magne- sium were comparable between the tolvaptan and furose- mide groups.