Can anyone tell me if the degree of sympathectomy is commensurate with local anesthetic strength? For example, does .5% bupivicaine cause more of a sympathectomy than .25% bupivicaine?
Thanks
Pain and sympathetic fibres are blocked first, motor fibres blocked later. So sympathetic blockade is very common with epidurals/spinals and peripheral blocks even with low concentration solutions. Once a threshold is reached, however, no further block occurs. I suspect this threshold is the same for sympathetic fibres as for pain fibres. Ie once you have acheived total analgesia with whatever solution you use, you have probably acheived maximal sympathetic blockade.
Hope this is clear enough. Why do you ask?
Thanks for your reply, Michael de Sousa. This was a question one of the other MDs and I had a friendly dispute over. I'm bummed to say I have now lost the bet! haha For some reason I received the impression in residency that sympathectomy was commensurate to local anesthetic strength, so I would typically use .25% bupivicaine in cases like AAAs where volume might become an issue. When I went into private practice, the group I joined always used .5% bupiv, hence the friendly dispute. Anyway I started doing what everybody else was doing (when in Rome do like the Romans) and never had a problem, but never could get a clear answer to my question. I wonder if there is any literature on this.?
While we're on the subject of epidurals,I tell you what, since we started doing thoracic epidurals for thoracotomies a few years ago I'm hooked (plus GA). Great band of analgesia at the surgical site and minimal volatile anesthetic and opiod requirement intraoperatively, not to mention nearly no pain postoperatively. We started working with a new heart surgeon a couple years ago and he was amazed how comfortable his patients were in the PACU and subsequent ICU stay.