[Sacamuelas]

Good post. A little background to let everyone know why this thread came about on Aprof.

This post was started to discuss the reasons behind and treatments for inadequate anesthesia in a severely infected local area. The original example was a severely abscessed tooth needing to be extracted. This process, however, is relevant to ANY area on the body that will need local anesthesia for debridement, treatment, etc. So this is relevant info for all.

Originally posted by troy2k
First, I will admit that I had terrible luck trying to find ANYTHING on this subject. However, here's what I've pieced together on the physiology of the subject.
There are 3 major features underlying inflammatory pain: a change in the peripheral sensitivity of high-threshold nociceptors--ie, increased sensitivity; an alteration in the chemical makeup of the neurons in the nervous system, a change in their properties and function-- called a phenotypic switch; and finally an increase in the excitability or the responsiveness of neurons within the central nervous system, and this represents central sensitization.

These are good explanations of the process that I had understood to describe the physiology behind increased sensitivity to stimulus in a chronic inflammation area. I.e.: a normally "non-threshold" level stimulus actually causing nerve discharge (reaching the threshold) due to physiological changes that led to increased "sensitivity" in the nerve bundle or CNS. This process is seen all over the body.. I.e.: a light touch on a "bruised" area causing the patient pain when that amount of pressure would never have caused a pain response w/o the prior inflammation in the area causing the changes you described.

That being said, these changes could be present in the original scenario in the mouth. A good review... but I don't think these side effects of inflammation are the cause of the lack of adequate anesthesia in an "infected" area. None of these things would cause a local anesthetic not to work as predicted.

Originally posted by troy2k
More importantly maybe is the proliferation of proteolytic substances, which may be responsible for the destruction (lysing) of opioid and amide receptor sites, inhibiting analgesic response.
As I said, at this point in time I found NO specific references to the phenomenon of decreased analgesia due to local infection. I have however researched this before. At that time there was little if any understanding as to the mechanisms involved. Much of this is still theory on my part, and I'd be glad to hear what others have found.

Not a proteolytic function..... good thinking though. That type of situation would not cause any of the common local anesthetics to cease working b/c they do not have "receptors" that can be blocked or destroyed. They work differently than opiod type analgesics. It is important to know how local works to understand why they don't work as well in infected environments. Anybody want to describe how local anesthetics block nerve transmission?

What happens to the local tissue environment in an infectious "abscess" or "cellulitis" situation? It isn't changes in the nerve that causes the anesthetic not to work in severely infected areas. The mechanism is well understood.... anyone else got any ideas?

Originally posted by troy2k
Now the important stuff: if you have a patient who falls into this category, it becomes a question of priorities. Will his peridontal infection lead to acute endocarditis? Do you want to send the patient away untreated with a regimen of PCN-VK, trusting in PT compliance? I know of at least one medic who did just that...with dire consequences. It may be worth running labs before you let the patient start a week long regimen.
Also worth consideration is the typical stoicism of third world patients. I've seen teeth pulled just as mentioned in the instigative article, ie, sans anesthesia. These are all factors in your patient care decisions.
For the most part however, peridontal infections can be treated safely with PCN (or perhaps Cipro for those with allergies), then a return visit can allow you to remove the tooth with greater patient comfort.

Will get to the rest of your post after we get through the cause for local anesthetic failure. Great post Troy. If you didn't know all the answers....trust me a LOT more people didn't either.