Beuthanasia-d is a barbiturate anesthesia which causes loss of consciousness and cessation of heart pumping at the doses we administer.   This effect is concentration dependent.  Another way of saying this is that the levels of drug are so active in the injection the affect is extremely quick, typically less than one minute.  By way of example, the active ingredient, pentobarbital, is sometimes used as a sedative, hypnotic for short term, preanesthetic and control of convulsions in emergencies.  The only difference between these effects and euthanasia is quantity administered.