I do thoracic RFA periodically and I hate every single one. Usually it's due to scoliosis or significant kyphosis secondary to osteoporosis (where we want to spare steroids). Anatomy is screwy, bones are barely more dense than the lung. You are almost imagining the transverse process, but if you miss you puncture a lung. Lateral view is less reliable since the spine is tortuous in these patients. Works well, but I get more grey hairs on each one.
I usually only do this if the thoracic facet steroid injections (which usually work well) don't last long of if they are super high risk for more steroids.
While over sedation does increase risk of bad things happening, the level of sedation has nothing to do with which drug was used.
It doesn't seem possible to me either, unless they were advancing in the lateral view and the needle went off track.