I don't understand why it's so hard to find drugs to kill people in a painless fashion.
Just about everyone has gone under for surgery before, and you don't feel a thing unless they don't give you enough anesthesia.
So just calculate how much you would give a normal person, multiply it by 10, and then kill them in any fashion you want.
That's basically exactly what happens.
They consciously feel a few things at first, and as others have stated in the thread, sometimes the IV sedation chemical burns as it courses through veins. That burning is mostly just the chemical reacting with each neuron it comes into contact with, and then the totality of it all ends up causing a suppression of actual feeling.
Just like anyone going under the knife, receiving a high dose of what they use causes the exact same thing. You could cut them up and they wouldn't feel a thing.
What happens AFTER they are already sedated is both the overdose on the sedative, and the other chemical, both proceed to course throughout the body and cause paralysis. It's rarely so perfect as going from conscious, to unconscious, to entirely paralyzed; it takes a little time for the paralysis agent and overall chemical OD to cause true brain death.
Guess what happens to your body, even when completely stone-cold unconscious, when the neurons in your CNS are still capable of acting on electrical potentials but otherwise cannot effectively communicate with the.. er, what is it, the medulla and basal ganglia? (the former being for autonomous motor controls, the latter voluntary motor control)
That would be the following: the neurons fire repeatedly and the connected skeletal muscles (and smooth cardiac muscle) constantly spasm, sometimes so violently they actually cause tears in the connective tissues/ligaments and rip free from the skeleton.
Guess what that looks like to an outside observer? It looks brutal.
Guess what the patient feels? Absolutely nothing.
Clarification: I admit I'm not sure if these chemicals cause the nerves to fire repeatedly, causing the muscles to spasm, or if they interact directly with the skeletal muscle tissue. The general means to the end should be the same: there's an interruption to certain metabolic processes, and/or ultimately a disruption at the cellular level, *I believe* mostly at the osmotic/electrolyte level which causes a sort of locked-on cellular response... in this case being the fully engaged taut position, which when uninterrupted causes spasm.
A true medical professional who understands these processes would tear apart what I just said, so it shouldn't be cited for important purposes. But it's going to be close enough for general understanding.
😉
That, and the end point is still the same: the "victim", er... the scumbag who got his/herself into that position in the first place, doesn't feel a damn thing once it progresses to the lethal point.
They only feel whatever might be felt during sedation.