How to Administer Dental Nerve Blocks A Training Guide

1. How to Administer Dental Nerve Blocks A Training Guide By Heidi Reuss-Lamky, LVT, VTS (Anesthesia)

2. Dental nerve blocks provide excellent pain management for many oral procedures. They are: *Easy and inexpensive to perform *Provide immediate relief *Work in concert with anesthetic and other analgesic modalities This training guide explains how to administer these blocks.

3. A nerve block is performed by injecting a small volume of a local anesthetic close to the nerve you want to desensitize. For information about indications and benefits, read “Administering Dental Nerve Blocks,” in the Articles for Technicians section of Journal of the American Animal Hospital Association (www.jaaha.org), Sept/Oct 2007.

4. The five basic dental nerve block regions: *Major palatine *Infraorbital foramina *Maxillary *Middle mental *Mandibular (also called inferior alveolar)

5. Major Palatine Block Located on the palate halfway between the palatine midline and dental arcade at mesial root of maxillary first molar Located at the palatal root of the maxillary fourth premolar

6. Major Palatine Block *Injection site can be difficult to identify *Palatine nerve is also branch of maxillary nerve Use of this block does not provide significant advantage over the others discussed in this training guide.

7. Infraorbital Nerve Block The infraorbital nerve has multiple sensory branches that innervate: *Nasal and buccal soft tissues *Incisor, canine and premolar teeth

8. Infraorbital Nerve Block In dogs, the foramen is located on the maxilla, dorsal to the caudal (distal) root of the third maxillary premolar.

9. Infraorbital Nerve Block The caudal extent of the infraorbital canal is located at the level of the medial canthus of the eye, which can serve as a guide for maximum needle advancement.

10. Infraorbital Nerve Block Use care with cats and brachycephalic dogs. Their infraorbital canals are short. Avoid inserting needles beyond the medial canthus. Caution!

11. Infraorbital Nerve Block (Cranial) This nerve block desensitizes: *Incisor, canine and premolar teeth rostral to the fourth premolar *Associated ipsilateral soft tissues

12. Infraorbital Nerve Block (Cranial) Perform this block at the opening of the infraorbital foramen, which can be accessed intraorally or extraorally using a percutaneous approach. *Do not insert needle deep into infraorbital canal. *Inject only small amount of local anesthetic (usually 0.25-0.5 mL). *After injection, apply pressure for 60 seconds while elevating patient’s head.

13. Infraorbital Nerve Block (Caudal) The caudal infraorbital nerve block desensitizes the same areas as the cranial block, plus all of the bone, soft tissue and dentition rostral to the maxillary first molar. The area affected depends on the degree of caudal diffusion of the anesthetic.

14. Infraorbital Nerve Block (Caudal) The caudal infraorbital nerve block is administered similarly to the cranial infraorbital block, except: *The head is kept elevated. *Digital pressure is applied over the foramen and needle during, rather than after, injection.

15. Infraorbital Nerve Block (Caudal) Pressure over the foramen and needle helps force the anesthetic caudally. Maintaining head elevation while placing digital pressure over the infraorbital canal after injection for 60 seconds encourages caudal flow deep into infraorbital canal and surrounding tissues.

16. Infraorbital Nerve Block (Caudal) Anadditional 50% of the anesthetic can be administered to encourage adequate diffusion to the middle superior alveolar nerves that lie within the infraorbital canal.

17. Infraorbital Nerve Block (Caudal) In cats, the infraorbital foramen is located above the maxillary second premolar and is within the junction of the zygomatic arch and maxillary bone.

18. Infraorbital Nerve Block (Caudal) A mature cat’s infraorbital canal is only about 4-mm long. It ends at the level of the medial canthus. A 27-gauge needed attached to a tuberculin syringe is inserted into the foramen and advanced into the infraorbital canal a maximum of 3-4 mm. Maintain pressure over site for up to 60 seconds after injection.

19. Infraorbital Nerve Block (Caudal) Unless the agent diffuses beyond the caudal borders of the infraorbital canal, adequate analgesia cannot be provided to the maxillary fourth premolars and molars. If anesthesia to the caudal cheek teeth is required, use the maxillary nerve block.

20. Maxillary Nerve Block This affects: *All of bone of the maxilla *Soft and hard palates *Soft tissue of the nose and upper lip *Dentition rostral to the second molar maxillary More anesthetic (up to 2 mL in very large breeds) can be used for desensitizing the orbit, eye, conjunctiva, eyelid and forehead skin.

21. Maxillary Nerve Block in Dogs Intraorally, insert the needle just caudal and center to the last maxillary molar. Advance the needle dorsally to just beyond the root tips of the last molar. Aspirate and slowly inject the agent. Note: This block is preferred over the infraorbital nerve block for providing analgesia to the maxillary molars.

22. Maxillary Nerve Block in Cats Intraorally inject at the base of the “V” notch or divot near the soft palate junction, palpable just medial to the caudal root tips of the maxillary fourth premolar. Aspirate and inject the agent slowly.

23. Middle Mental Block This block disrupts sensation to all of the ipsilateral canine and incisor teeth as well as bone and soft tissue rostral to the second premolar of the mandible. If deposited outside of the foramen, only the ipsilateral buccal soft tissue from the canine teeth forward with be numbed. Can be performed intraorally or percutaneously.

24. Middle Mental Block Location of the middle mental foramen varies with breed, size and species of the patient. Although easily palpable in larger dogs, the foramen can be hard to palpate in smaller ones. Dental radiology may help locate the foramen in cats and small breeds of dogs.

25. Middle Mental Block for Dogs The middle mental foramen is located ventral to the rostral (mesial) root of the second premolars. If the area cannot be palpated, inject in the submucosa at the ventral third of the mandible at the diastema between the first and second mandibular premolars. While injecting, place finger over needle to help direct the anesthetic into the foramen.

26. Middle Mental Block for Dogs Inject slowly. Otherwise, as the agent goes directly into the canal, pain may cause a rise in the heart rate. Apply pressure for 60 seconds after injection to ensure maximum caudal diffusion into the foramen. Caution!

27. Middle Mental Block for Cats The middle mental foramen in cats is very small and difficult to locate. The foramina of the middle mental nerves are at the apex of the mandibular canine tooth and the targeted foramen is located most rostrally.

28. Middle Mental Block for Cats This block is performed similarly to the dog, but a 27-gauge needle may allow easier access. Because the middle mental nerve block provides limited relief to the circumscribed part of the mandible, the mandibular nerve block may be a more practical alternative for cats.

29. Mandibular or Inferior Alveolar Nerve Block This block numbs the lower dental arcade (including teeth and bone on the ipsilateral side) as well as the associated soft tissues (possibly the tongue) that are innervated by the mandibular nerve. This block can be performed either intraorally or percutaneously.

30. Mandibular or Inferior Alveolar Nerve Block The foramen is located on the medial side of the ramus of the mandible in dogs and cats. The mandibular nerve fossa can be easily palpated intraorally in most dogs. It is located approximately two-thirds of the distance caudally from an imaginary line drawn from the bone beginning after the last mandibular molar to the caudal prominence of the angular process of the mandible.

31. Mandibular or Inferior Alveolar Nerve Block To determine the site extraorally for percutaneous drug injection, palpate the vascular notch located on the ventral aspect of the mandible. Place the needle into the medial aspect of the mandible. Intraoral palpation of the needle during injection can help ensure proper needle placement.

32. Mandibular or Inferior Alveolar Nerve Block Because the foramen cannot be directly entered, the nerve is blocked before it enters the mandible. Analgesia is accomplished secondary to regional diffusion of the anesthetic. Make sure the bevel of the needle is facing the foramen. Aspirate and slowly inject the agent.

33. Caution! Mandibular or Inferior Alveolar Nerve Block Inadvertent inclusion of the lingual nerve can cause self-mutilation of the tongue and lip-chewing upon recovery. This requires sedation of the patient until the agent disperses.

34. Splash Block Another technique that may be used for local pain control in oral surgery is the splash block. Place the local anesthetic directly into a surgical site or inject into a closed space where the agent may diffuse.

35. Supplies, Drugs and Dosages To perform a dental nerve block, you’ll need: *Tuberculin or 3-cc syringes *30- to 22-gauge, ¾- to 1 3/8-inch needles *Regional anesthetic agent

36. Supplies, Drugs and Dosages The most commonly used agents include lidocaine, mepivicaine and bupivicaine. Adding epinephrine reduced the rate of absorption by about 30% and can increase the effect and duration by up to 50%. Epinephrine also aids in hemostasis.

37. Supplies, Drugs and Dosages The most commonly used dental block agent is 0.5% bupivicaine combined with epinephrine at 1:200,000. This preparation is also available in 1.8-mL individual dose cartridges that can be used with dental aspirating syringes.

38. To learn more about suggested drugs and dosages (including toxic dosages), see “Administering Dental Nerve Blocks”, an Article for Technicians in the Journal AAHA, September/October 2007 (Vol. 43, No. 5), www.jaaha.org.

39. Toxicity and Complications of Local Anesthetics Although rare, systemic toxicity from local anesthetics can result in CNS signs that include: *Muscle twitching *Seizure *Depression *Unconsciousness *Coma *Respiratory arrest These signs can be masked in the anesthetized patient.

40. Toxicity and Complications of Local Anesthetics Metabolites or preservatives of local anesthetics can also cause rare allergic-type reactions. The most common indicators of anaphylaxis are cutaneous and respiratory reactions that are secondary to accidental intravenous injection or excessive doses of local anesthetics. Methemoglobinemia is also possible.

41. Toxicity and Complications of Local Anesthetics All patients should be closely monitored in the hours following the administration of a dental block. Although infrequent, some animals may self-mutilate by chewing on their desensitized lips and cheeks. Excessive pawing of the face may also occur. In these cases, tranquilization may be necessary.

42. Summary: Dental nerve blocks are inexpensive to perform, easy to master and can significantly benefit patient comfort. When combined with other analgesic modalities, they are a valuable part of a balanced anesthetic and analgesic protocol.

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44. This training guide was excerpted from “Administering Dental Nerve Blocks,” an Article for Technicians written by Heidi Reuss-Lamky, LVT, VTS (Anesthesia) in the Sept./Oct. 2007 issue of The Journal of the American Animal Hospital Association (www.jaaha.org)