Introduction
The utilization of regional nerve blocks for oral surgery in dogs and cats is synonymous with quality patient care. This article
details techniques that can be incorporated into the companion animal hospital dentistry service to maximize safety, care
and comfort for patients undergoing oral surgical procedures. This discussion also suggests adopting less misleading names
for the regional nerve blocks relying on simple anatomical regions blocked rather than the traditional confusing nomenclature.
Detailed descriptions of regional and local nerve blocks commonly utilized to provide analgesia for oral surgery in veterinary
patients have appeared in numerous publications.1,2,3,4 Complete analgesia to the targeted tissue and a reduction in the concentration of the inhalant anesthetic are two significant
benefits of proper administration of local agents.1 Hypotension, bradycardia, and hypoventilation are complications that can be minimized by the use of local and regional
blocks for oral surgery.3 Local blocks eliminate the perception of pain making surgical anesthetic depths unnecessary.
Agents
This author commonly uses lidocainea and bupivicaineb combined in the same syringe for regional oral nerve blocks. Lidocainea is not desirable as a sole agent due to its limited effect post administration (1-2 hours5 ). Bupivicaineb requires administration much earlier in the anesthetic event than lidocainea in order to be effective prior to surgical tissue manipulation. These limitations can be minimized or eliminated by using
them in combination. The quick onset of lidocainea coupled with Bupivicaine'sb extended duration of effect (up to 8 hours5 ) make them a good choice for combined use in regional nerve blocks. The agents may be used with or without epinephrine.
Although rare, complications are possible with inadvertent systemic administration or systemic uptake of locally delivered
local anesthetic agents. Central nervous system excitement including seizures followed by depression, apnea, severe cardiovascular
compromise, dysrhythmias and hypotension are all possible.5 Direct toxicity to skeletal muscle and anaphylactic reactions
are possible with local administration.5 The author has never experienced any of these complications at the doses recommended
in this article.
Table 1
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A maximum dose of 1.0 mg/kg of each agent in combination in the same syringe is recommended. Care should be exercised, especially
in smaller patients and cats, so that maximum doses are not exceeded. The ratio of lidocainea:bupivicaineb is 1:4 when using
concentrations of 2% and 0.5 % respectively. The total volume used depends upon the size of the patient and the number of
sites that require analgesia. The maximum number of sites would be four if the patient requires surgical manipulation in all
four quadrants. Table 1 shows recommended infusion volumes per site based upon patient size. Please note that these volumes represent both agents
mixed together. Table 2 shows a sample calculation for a 4 kg dog.
Table 2
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Physiologic parameters will determine if the block is effective. If blood pressure, heart rate and respiration rate increase
with surgical manipulation the block either was not correctly placed or hasn't had the proper amount of time for onset. (5
minutes) If enough time has elapsed to be comfortable that onset is not an issue the block may be repeated as long as the
maximum total dose is not exceeded. It should be noted that the low ph of inflamed tissue will render local anesthetics less
effective.
