i have an excellent reptile vet and i have had several conversations with him on reptile surgeries and other topics realted to the big no no E word (thats...ear muffs reptile evolution).
according to him there is a low survival rate for sedation on reptiles. sedation is really hard on their systems. even during a "routine" procedure, the surivial rate is low.
also, there are new finidngs in scientific journals that the primative nerves of reptiles don't really feel pain as higher order animals. makes sense when you think about how a snake or lizard will burn itself do death on a heat rock.