Oklahoma, which one of the state's that had some embarrassing episodes with executions, recently legalized the use of nitrogen asphyxiation for executions, I don't know why they haven't switched to that. Asphyxiation, commonly using nitrogen, using some sort of apparatus that still allows carbon dioxide to be expelled normally is a relatively pleasant way to go, it's a popular way for those intentionally ending their lives due to medical conditions to die.
Oklahoma recently produced a report on a botched execution which described a keystone cops sort of scenario relating to IV access to administer the drugs. A paramedic made the first attempt at access and was able to get an 18 guage in the AC with good flash, but he did not have any tape or dressing ready to go, so he left to find some, by the time he found some tape the IV was no longer in place. He then made numerous other failed attempts at which point the physician attempted a subclavian central line access, but had no ultrasound so couldn't get it correctly into the vein, an EJ was attempted and failed, finally the physician decided to place a femoral line, but with a 1.5 inch peripheral IV, there was another central line kit available for use but it did not occur to the physician that this would be better for femoral access. The femoral line was described as "positional" but working, the site was covered to maintain privacy and the execution drugs were infused, and for some reason the drugs were working but not very well and was basically obvious distress someone checked the IV site and there was a large infiltration, he was eventually moved to another room and died later.
As it turns out, there was no apparent puncture to the femoral vein, the IV placed there was only infusing into the subcutaneous tissue, although it is surprising that a fair amount of the drugs did make it's way into circulation through capillary absorption.