General anesthetic prior to death sentence?

In the current GD thread wherein many lament the ‘suffering’ of the late Clayton Lockett ostensibly caused by his “botched” execution, I posted the following which I think is apropos to this thread:

With the above in mind, let me ask the good doctor Qad (or anyone else who knows the answer)- in the US, are physicians forbidden by their various professional organizations from participating in executions? And, if ‘anesthesia assistants’ (or whatever they’re called) are used in the US, could they not do the job?

Is it really the case that finding someone qualified to administer IV drugs is difficult, or is that most qualified personnel are prohibited from doing so?

Thanks!