Lethal Injections Humane or Not?

I am still undecided where I stand on the death penalty, however, I definitely think that if someone is going to be sentenced to death it should be quick and painless, without suffering. Lethal injection is supposed to be just that, right? Well.... maybe not in all cases or all of the time.

"In cases where the injection was botched and drugs were delivered into muscle or under the skin rather than into the veins, prisoners would be fully aware as the paralysis took hold and the potassium chloride was administered, said Teresa Zimmers, who led the study.
"It would sort of be the equivalent of slowly suffocating while being burned alive," Zimmers said.

That was likely the experience of Florida inmate Angel Diaz, who took 34 minutes to die in December after the needles were inserted improperly."

Theoretically people getting these injections shouldn't feel anything at all. They are given an anesthetic, thiopental, that is supposed to "render the inmate unconscious while the other drugs do the job." as well as potassium and pancuronium. However, sometimes they don't dose the anesthetic appropriately for the person's body size which could leave someone conscious when they should not be (according to the linked article above).
Now let me tell you a couple things about potassium: first of all it BURNS going in. Even in lower concentrations than I imagine they must use for lethal injection, patients will tell you it hurts... a lot. Second, the only time I have heard of potassium effectively stopping the heart 100% of the time is in the operating room where open heart surgeons fill the heart's circulation with a potassium solution in place of the patient's blood. Now, I am by no means an expert on such things, and I know people can and have died from getting IV potassium but, efficacy aside, if they feel the potassium going in, that doesn't exactly qualify as painless in my book.
The last drug, pancuronium bromide, is a paralytic. That means it paralyzes all of the muscles in your body. It doesn't render you unconscious but it will prevent you from moving and breathing. This isn't necessarily a problem when you are giving it to someone who is going to die anyway but... if you are awake when this drug is affecting you, you will be able to feel yourself slowly suffocating to death. So much for not suffering.