One of the most difficult situations for both the practitioner and the patient is when adequate pain control cannot be accomplished during a procedure. This may be very challenging, especially when the patient is experiencing an infection.
In these cases, the patient may present with pain alone or in conjunction with swelling. It is important to understand the pharmacology of the local anesthetics and the physiology of the infection in order to optimize patient care.
Local anesthetics present in two chemical states, a weak base or a unionized form that penetrates tissue and an impermeable cationic state that does not penetrate tissue very well. When the local anesthetic is administered into an infected environment with a low ph, there will be a greater concentration of the cationic form. (1)
The clinical effect will result in delayed onset and decreased intensity of the local anesthetic. Another theory proposed is that in an infected area there are degenerative and inflammatory changes found in the nerve structures. (2)
These findings support the need for administration of nerve blocks, as opposed to local infiltration. This will allow the local anesthetic to be administered away from the infected site.
When administering the local anesthetic as a block in an infected environment, it is imperative to change the needle. Using the same needle will cause seeding of the tissue into deeper tissue planes.
Never inject directly into tissue that is under pressure from the abscess. You must first establish some form of drainage prior to local infiltration. This will be much more comfortable for the patient and you will not tract the infection into deeper tissue planes.
The local anesthetic that has the closest Pka to the tissue Ph will demonstrate the quickest onset time. Mepivacaine falls into this category and is a great anesthetic to use in an infected patient when the lidocaine is not doing the job. (3)
Mepivicane is best administered in plain form, without the vasoconstrictor in order to help overcome the acidity created by the infection.
Using a larger amount of the local anesthetic (but not exceeding the maximum recommended dose) will allow a greater concentration of the unionized form to penetrate the tissue. Other techniques for increasing the volume of local anesthetic to the infected site include periodontal ligament injection and interseptal injection technique.
Most important of all, you must have patience and allow adequate time for the local anesthetic to take effect. This may take up to 10-15 minutes. During this time, it may be helpful to place the patient in an upright position.
Treating the infected patient has many challenges and satisfactory results may not always be achieved, despite the aforementioned techniques.
At this point, there are two final options available. One is to place the patient on antibiotics and have them return another day or you can refer them for treatment under general anesthesia. Communication plays a major role in these situations, and the patient must be prepared for all possible outcomes.
- Hersh EV, Condouris GA: Local anesthetics: A review of their pharmacology and clinical use. Compend Contin Educ Dent 1987,8:374-382
- Brown RD: The future of local anesthesia in acute inflammation: Some recent concepts. Br Dent J 151:47, 1981
- Jastak JT, Yyagieva JA Donaldson D: Local anesthesia of the oral cavity. Philadelphia WB Saundes 1995