Lecture 9: local anesthesia Flashcards
Role of the vet tech for local blocks
It is important to understand this is only basic introductory information
If administering local anesthesia is a task performed by RVTs in your clinic it is recommended to investigate further CE and practice
State and provincial laws will vary – ensure you understand the legality of RVTs performing local anesthesia in your area
Local anesthesia needs to be PRESCRIBED
This means the decision falls out of an RVT’s scope of practice and must be made by a DVM
Local anesthesia is used for
Local anesthesia is used to:
Reduce the depth of general anesthesia required
Control pain after the procedure
Local anesthesia can minimize what risks
Can minimize complications such as:
Hypoventilation
Hypotension
Bradycardia
Bupivacaine is and whats it onset of action and duration of action
Bupivacaine 0.5% (or 5 mg/ml) is the drug of choice for local anesthesia in dentistry
Using with epinephrine may decrease chance of toxicity, but is not required
Onset of Action:4 to 8 minutes
Duration of Action: 6 to 10 hours
Possible Medication Reactions to local block
Possible but rare reactions include:
Toxicity to skeletal muscle
Anaphylactic reactions
Permanent nerve damage
Rule of Thumb to avoid toxicity:
Never exceed 2.0 mg/kg in cats and dogs
Must take into consideration size of patient AND number of sites that require anesthesia
Effectiveness of block is noted by
Must be evaluated after administration
Increase in respiratory rate, heart rate, and/or blood pressure caused by surgical manipulation indicate ineffective block
What to do if the block was not effective
Block has not had time for onset or
Was not performed correctly
Blocks may be repeated as long as maximum dose not exceeded
Infiltration Blocks is
Least effective method
Used after a procedure to reduce postoperative discomfort
Do not block entire quadrant, only area where administered
Equipment
25 – 27 gauge needle
1 cc syringe (dental local anesthesia syringe can be used)
Technique
Proper dose infiltrated around the tissues
Advantages and disadvantages of regional blocks
Advantage
Ability to block entire quadrants
Disadvantage
Transient loss of sensation and function to area blocked
Possibility of postoperative self-inflicted injury to tissues
General technique of regional blocks
Needle advanced slowly to desired location
Syringe plunger drawn back to perform aspiration to ensure not in a vessel
If no blood: agent slowly injected, digital pressure applied over foramen for 1 minute after needle withdrawn
If blood: digital pressure put on the site and a new syringe and needle should be used to repeat the procedure
Technique for dogs and cats are similar
Both maxilla and mandible have rostral and caudal blocks
Infraorbital block block what teeth and what nerve
Infiltrates infraorbital nerve via infraorbital canal
Incisors
Canines
Premolars 1 – 3
Maxillary bone and surrounding soft tissue
Technique for infraorbital blocks
Retract lip dorsally and palpate just dorsal to distal root of maxillary 3rd premolar
The infraorbital neurovascular bundle can be palpated as a large cylindrical band that exits the infraorbital canal
Retract bundle dorsally with digit of non-syringe holding hand
Needle advanced close to maxillary bone ventral to bundle in a rostral-caudal direction to just inside the canal
Needle should pass without hitting bone
If bone encountered, slightly withdraw needle and redirect
Proper insertion confirmed by gentle movement of syringe as needle hits infraorbital canal wall
maxillary block blocks what teeth and what nerve
Infiltrates infraorbital nerve and sphenopalatine nerves
All maxillary teeth on side of infiltration
Adjacent bone and soft tissue
Infraorbital technique for maxillary block
Needle is placed as per Rostral Maxillary block and then advanced more caudally
Proper needle size must be used
In cats and brachycephalic dogs the infraorbital canal is very short
Important to keep syringe and needle parallel to dental arch line of maxilla
Very little space between entrance of foramen and orbit
perpendicular technique for maxillary block
Mouth must be opened wide
Lips and cheek are retracted dorso-caudally
Needle inserted perpendicular to the palate just caudal to the second molar
Inserted to a depth of 4 – 7 mm depending on size of patient
Should reach just beyond the apex of the second molar roots
Will be inserted to point just before the infraorbital and pterygopalatine nerves branch
Middle mental blocks are and block what
Infiltrates the inferior alveolar nerve within the mandibular canal via the middle mental foramen
Anesthetizes:
Incisors
Canines
Premolars 1 and 2
Middle mental block technique
Landmark for infiltration is the mandibular labial frenulum
This is retracted ventrally
Needle inserted at the rostral aspect of the frenulum
Advanced along mandibular bone (at about 30 degree angle to body of mandible) to just enter the mandibular canal
Located ventral to mesial root of second premolar at 1/3 the distance between the ventral and dorsal mandibular borders
If bone is encountered, needle is backed out and redirected until passes freely into foramen
If properly seated in the canal, the mandible will move slightly upon infiltration of drug
Inferior alveolar blocks what teeth and what nerves
Infiltrates the inferior alveolar nerve on lingual aspect of mandible as it enters the mandibular canal
Anesthetizes:
All the teeth of the mandible on the side infiltrated
Adjacent bone and soft tissue
Inferior alveolar technique 1
Extraorally palpate the notch just dorsal to the angle of the mandible and ventral to the condylar process
Needle advanced intraorally along lingual aspect of mandible just caudal to the third molar (K9) or first molar (Fel)
Mandibular first molar is missing in feline so must palpate mandibular notch and approximate position of first molar
Needle directed midway between where tooth would be and the notch
The nerve is located outside of the mandibular canal at this point so needle tip must be located caudal to the foramen and rostral to angular process of mandible
Inferior alveolar technique 2
Use the lateral canthus of the eye as a landmark
A line is drawn from the lateral canthus directly to the ventral mandible
Needle is inserted into skin at lingual aspect of ventral mandible
Needle is advanced along bone following the line to a point 1/3 of the distance from ventral to dorsal mandible
Needle will now be in the vicinity of mandibular foramen where inferior alveolar nerve enters mandibular canal
Extraoral technique for the inferior alveolar block
Extraorally palpate the indentation on the ventral border of the caudal mandible just rostral to the angular process
This indentation should be in the same rostral-to-caudal plane as the lateral canthus of the eye
If having issues palpating the indentation, use the lateral canthus as a landmark
Pass the needle into the skin on the lingual aspect of the caudal extent of the indentation
With needle parallel to lingual aspect of mandible, advance it along the bone until it reaches 1/3 of the distance from the ventral to dorsal mandible
Needle will now be in the vicinity of the mandibular foramen where inferior alveolar nerve enters the mandibular canal
