9 - local anesthesia

Question 1

What is the role of a vet tech in regards to local anesthesia?

Answer 1

If administering local anesthesia is a task performed by RVTs in clinic then recommend to do 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 need to be prescribed - meaning decision it out of RVT scope and made by DVM

Question 2

Why do we perform local anesthesia?

Answer 2

used to reduce depth of GA required and for pain control after procedure
Can minimize complications like hypoventilation, hypotension, bradycardia

AKA blocks, local blocks, dental blocks

Question 3

What is bupivacane? Onset of action? Duration?

Answer 3

bupivacaine 0.5% (or 5mg/ml) is drug of choice for local anesthesia in dentistry
using epinephrine may decrease chance of toxicity, but it is not required

Onset of action: 4-8 mins
Duration of action: 6-10 hrs

Question 4

What are possible medication reactions when using bupivacaine?

Answer 4

toxicity to skeletal muscle, anaphylacrtic reaction, permanant nerve reaction

rule of thumb to avoid
never exceed 2.0 mg/kg I cats and dogs
Must take into consideration size of patient AND number of sites that require anesthesia

Question 5

What is the rule of thumb to avoid toxicity in cats and dogs?

Answer 5

never exceed 2.0 mg/kg in cats and dogs

Question 6

What is the accepted volume of bupivicane PER SITE in cats/sm dog, med dog and lg dog?

Answer 6

Cat/sm: 0.1 ml
Med: 0.2 ml
lg: 0.3ml

Question 7

How can we evaluate effectiveness of a block?

Answer 7

evaluate after administration
increase in RR, HR, and or BP caused b surgical manipulation indicate ineffective block
this can occur either bc block has not had time for onset or was not performed correction
blocks may be repeated as long as the max dose is not exceeded.
Meaning, on injection, heart monitor should freak out a second then chill - MEANS GOOD!
Blocks can be repeated long as it doesn’t exceed max dose

Question 8

What is infiltration blocks?

Answer 8

least effective
used after procedure to reduce postoperative discomfort
do not block entire quadrant, only area where administered
equipment: 25-27g needle + 1cc syringe (or dentle syringe)
technique - proper dose infiltrated around the tissues

Question 9

What are regional blocks? advantage/disadvante? equipment?

Answer 9

advant: blocks entire quadrants
disadvant: transient loss of sensation and function to area blocked. possibility of postoperative self-inflicted injury to tissues
Equipment - 25-27g needle + 1 cc syringe, may require 1 1/2” needle

Question 10

What is the general technique of regional blocks?

Answer 10

needle advanced slowly to desired location
syringe plunger drawn back to perform aspiration to ensure not in vessel
if no blood: agent slowly injected, digital pressure applied over foramen for 1 min after needle withdrawn
If blood: digital pressure put on the site and a new syringe + needle should be used to repeat the procedure
technique for k9/fel similar
both max/mand have rostral/caudal blocks

Question 11

What does the infraorbital block anesthetizes?

Answer 11

I’s, C’s, P1-3 and max bone and surrounding soft tissue
infiltrates infraorbital nerve via infraorbital canal

Question 12

How do we perform a infraorbital block?

Answer 12

retract lip dorsally and palpate just dorsal to distal root of max 3rd Premolar
the infraorbital neurovascular bundle can be palpated as a large cylindrical band that exits infraoribal canal. retract bundle distally w/ digit of non-syringe holding hand
needle advanced close to maxillary bone ventral to bundle in a rostral-caudal direction inside canal
needle should pass without hitting bone - if bone, withdraw and redirect
proper insertion confirmed by gentle movement of syringe as needle hits infraorbital canal wall

Question 13

What does the caudal maxillary regional block anesthetize?

Answer 13

all max teeth on one side + bone and surrounding tissue
two techniques to preform block
infiltrates infraorbital nerve and sphenopalatine nerves

Question 14

What is the technique to the caudal maxillary regional block when doing the infraorbital technique?

Answer 14

needle placed as per rostral max block and then advanced more causally - proper needle size must be used
In cats/brachycephalic dogs the infraorbital canal is VERY short - important to keep syringe and needle parallel to dental arch line of maxilla and have very little space between entrance of forament and orbit

Question 15

What is the perpendicular technique when doing the caudal maxillary block?

Answer 15

mouth wide open, lips/cheek retracted dorso-caudally
needle inserted perpendicular to the palate just caudal to the second molar
inserted 4-7mm (should reach just beyond apex of 2nd molar roots)
will be inserted to point just before the infraorbital and pterygopalatine nerves branch

Question 16

What is the middle mental rostral mandiblar block? what does it anesthetize?

Answer 16

I’s, C’s, P1-2

infiltrates the inferior alveolar nerve within the mandibular canal via the middle mental forament

Question 17

What is the technique for the middle mental block?

Answer 17

landmark for infiltration is mand labial frenulum, retract ventrally
needle inserted @ rostral aspect of frenulum. Advance along mand bon @ 30 degree to body of mand, to just enter mand canal. Loc ventral to mesiate root of 2nd P @ 1/3 the distance btw ventral and dorsal mand borders. if hit bone, back out and redirect until in foramen. If seated, mandible will move slightly upon infiltration of drug

Question 18

What does the caudal mandibular (inferior alveolar) block anesthetize?

Answer 18

infiltrates the inferior alveolar nerve on lingual aspect of mandible as it enters the mandibular canal
anesthetizes all teeth of mandible on same side infiltrated, adjacent bone and soft tissue
two techniques - intraoral injection and extraoral injection

Question 19

How is the procedure for the intraoral injection of the caudal mandibular, by caudal to 3rdM k9 or 1M in fel

Answer 19

Extraorally palpate the notche just dorsal to the handle of the mandible and ventral to the condylar process
needle advanced intraorally along lingual aspect of mandible just caudal to the 3rd M in K9 and 1stM in feel (mand 1M is missing in feline so must palate mandibular notch and approx position of 1st M) (needle directed midway btw tooth would be and the notch)\
nerve is loc outside of mand canal so needle tip must be loc caudal to foramen and rostral to angular process of mand

Question 20

What is the caudal mandibular intraoral technique where we use the lateral canthus of the eye as a landmark?

Answer 20

use lateral canthus of eye as landmark
line drawn from lat canthus directly to ventral mand
needle inserted into skin @ lingual aspect of ventral mandible
needle advanced along bone following line to a point 1/3 of distance from ventral to dorsal mand
needle now in vicinity of mand foramen where inferior alveolar nerve enters mandib canal

Question 21

WHat is the procedure for the caudal mandibular block using the extraoral injection technique?

Answer 21

palpate indention on the ventral border of caudal mand just rostral to angular process (in same plane as rostral-caudal plane as canthus of eye)
if issues palpathing, use lat canthus of eye as landmark
insert needle on lingual aspect of caudal extent of indentation
w/ needle parallel to lingual aspect of mand, advance along bone until 1/3 of distance from ventral to dorsal mand
needle now in vicinity of mand foramen where nerve enters mand canal