To euthanize a 15 kg animal with a saturated K+ solution, you would typically (after anaesthesia) inject 150 mg of KCl per kg. Assuming a 15 kg animal has a blood volume of about 70 mL/kg, and assuming all of the KCl injected is immediately introduced into the blood, and assuming a normokalemic concentration of 4 mM, what is the percent change in blood [K+] immediately post-injection? And how does this usually stop the heart instantly?