Chapter 12 Regional and Local Anesthesia
GENERAL COMMENTS
• Local dental nerve blocks can be performed in conjunction with general anesthesia for greater pain relief and reduced general anesthetic levels during oral surgery procedures.
LOCAL ANESTHETIC AGENTS
• Onset time for analgesia is longer with the longer acting agents such as bupivacaine. The onset time for bupivacaine is often as long as 30 minutes, whereas the onset time for lidocaine is only a few minutes. For this reason, it is common to use a 50-50 mixture of long-acting and short-acting local anesthetic agents.
• Local anesthetic agents may be purchased in carpules, which contain 1.8 cc, or in larger multi-dose bottles.
• Local anesthetic agents enter and occupy ion channels in the nerve cell membrane, preventing depolarization and the conduction of pain impulses.
Location for Blocks
• Regional blocks are introduced at the nerve foramen and create anesthesia of the regional teeth and associated soft tissues.
• Local blocks are accomplished by injecting anesthetic into the periodontal space or gingiva surrounding the tooth. Local blocks provide anesthesia only for the limited area directly perfused by local infiltration.
Dosage
• Total maximum dosage of bupivacaine for cats and dogs is 2 mg/kg.3 The total dosage for lidocaine for the dog is 5 mg/kg and 1 mg/kg for the cat.
• Toxic doses are additive. If a mixture of two local anesthetic agents is being used, it is recommended the maximum dosages be reduced by 50% to prevent inadvertent overdosage.
• Bupivacaine is potentially cardiotoxic; therefore, the lowest possible dosage should be used, which should not exceed 2mg/kg as a total cumulative dosage.
• A 5-kg cat could tolerate 10 mg of bupivacaine, or a total of 2 cc (just over one carpule). Generally 0.25 cc per site is adequate.
Instrumentation
• A 1.5-inch 27-gauge needle, on a dental anesthetic syringe, is designed to be used with the anesthetic carpule and works most effectively.
• Alternatively, a 1-ml syringe with a 27-gauge hypodermic needle can be used to withdraw the anesthetic from the carpule and infiltrate it into the site.