Potassium is K on table of Elements. Sodium is Na. With that being said potassium chloride is written for patients who take diuretics as it is flushed out of body by the excessive urination. Doctors typically write it in milliquivalents. Electrolytes have to be checked frequently as it can build up in the body and cause problems like tachycardia from hyperpotassemia. Im sure large doses as used for execution causes heart trauma of some kind.