LOCAL ANAESTHETIC

Question 1

for maxillary anaesthesia, what nerve are we achieving to block?

Answer 1

the trigeminal nerve trunk which then branches off to the posterior superior alveolar nerve, the middle superior alveolar nerve, the anterior superior alveolar nerve and then another small branch known as the infra orbital nerve

Question 2

what teeth would we PALATALLY INFILTRATE due to the unique/difficult anatomy of the teeth

Answer 2

the UPPER 6’S due to the zygomatic arch and divergent roots
the UPPER 2’S due to the apex of the root lying palatally - APEX IS WHERE WE AIM FOR WHEN INJECTING LOCAL!!!!

Question 3

what type of anaesthetic would we normally use when doing an infiltration (maxillary anaesthesia)

Answer 3

lidocaine (normally) - GOLD STANDARD

Question 4

what, of the anatomy of the mandible, makes it difficult for anaesthetic to diffuse through

Answer 4

the thick outer cortical bone

Question 5

what type of anaesthetic would we normally use for mandibular anaesthesia

Answer 5

articaine

Question 6

for LA, what nerve are we anaesthetising

Answer 6

the TRIGEMINAL NERVE - MAXILLARY AND MANDIBULAR DIVISON!

Question 7

PALATALLY, what are the nerves for anaesthesia

Answer 7

nasopalatine (incisive branch coming off of the nasopalatine nerve!), greater, lesser!

Question 8

advantages of infiltrating rather than block

Answer 8

lower risk of intravascular administration, local haemostasis (wound healing/clot?), its local diffusion - accuracy is better as a smaller region to anaesthetise, it acts on nerve ENDINGS rather than the trigeminal trunk

Question 9

advantages of ID BLOCK rather than infiltration

Answer 9

acts on nerve trunk, widespread effect from one single injection rather than many, can deposit away from infected areas?

Question 10

what is aspiration?

Answer 10

it is a technique used to reduce the risk of intravascular injections.
if there is blood - then likely to be in a vessel, if no blood - then less likely to be in a vessel

Question 11

what nerve(s) is involved in mandibular anaesthesia

Answer 11

the main nerve is the IAN (inferior alveolar nerve). branches off of this are the lingual, buccal, mental and incisive nerve.

Question 12

explain the procedure for carrying out an IDB

Answer 12

patient should be supine (think vasovagal), place the thumb on coronoid notch of ascending ramus of mandible, inject lateral to the pterygomandibular raphe (soft tissue triangle sort of), leave 1cm out - 2-2.5cm in.

Question 13

what is the KEY sign that the IDB has worked

Answer 13

a numb LOWER LIP!!!!!! (ipsilateral - whatever side you do your block on)

Question 14

can we carry out bilateral blocks

Answer 14

NO! either infiltrations OR 1 block and 1 infiltration

Question 15

what division of the trigeminal nerve are we blocking when carrying out a BLOCK (IDB)

Answer 15

the mandibular division

Question 16

what are the nerves involved for mucosal innervation for mandibular LA

Answer 16

lingual nerve, long buccal and mental

Question 17

what is the minimum amount of LA we can inject when doing an IDB

Answer 17

half a cartilage - 1.5-2.2ml

Question 18

for the MANDIBULAR incisors, would we do a block?

Answer 18

NO - this is because there it crossover so luckily there is actually thinner bone here therefore we can carry out an infiltration quite nicely to anaesthetise that area.

Question 19

what makes up an LA cartilage

Answer 19

2.2ml
anaesthetic agent
vasoconstrictor
preservative for shelf life
isotonic carrier

Question 20

describe the structure of LA

Answer 20

has a lipophillic end and a hydrophillic end with an intermediate chain in the middle - there are two types of intermediate chains it can either be an ester or an amide

Question 21

name the types of LA under the ester group

Answer 21

procaine, benzocaine (topical)

Question 22

name the types of LA under the amide group

Answer 22

lidocaine, prilocaine, mepivicaine, bupivicaine, articaine

Question 23

describe how LA works

Answer 23

it works by REVERSIBLY blocking LA channels (no depolarisation or action potential)

Question 24

describe the specific receptor theory

Answer 24

LA binds to Na channels and inactivates the Na channels. Must be able to pass through lipid membrane, must be able to bind to Na channels (hydrophillic)

Question 25

what 2 states do anaesthetics exist?

Answer 25

UNCHARGED (lipophillic) and CHARGED (hydrophillic)

Question 26

what do we do if there is a site of infection

Answer 26

WE NEVER PUT LA IN AN INFECTED SITE. this is due to the fact that there is a low ph meaning an increased conc of hydrogen ions.

Question 27

what LA has the best lipid solubility?

Answer 27

articaine has increased lipid solubility

Question 28

what does LA cause

Answer 28

VASODILATION , increased blood flow (systemic uptake and decreased duration due to it being taken away from the site)

Question 29

process of LA/how it works

Answer 29

absorbed into blood stream, distributed INTO TISSUE ONLY, metabolised (mainly in the liver) - articaine is the exception as it is in liver and plasma!

Question 30

role of a vasoconstrictor in LA

Answer 30

counteracts vasodilation of LA , reduces blood flow, increases speed of onset, reduced haemhorrage

Question 31

what is the MAX doss when administering lidocaine (with adrenaline)

Answer 31

7 cartilages (300mg), 1 cartilage for every 10kg

Question 32

when would we avoid using lidocaine with adrenaline

Answer 32

avoid with cardiac (unstable angina) issues or allergy (use prilocaine)

Question 33

what LA’s would we use with pregnant mothers

Answer 33

mepivicaine

Question 34

what does the thiophene ring in articaine do

Answer 34

its part of the amide ring and ester group. it increases lipid solubility, meaning v good diffusion

Question 35

what are some problems with LA in terms of the anatomy of the patient

Answer 35

shape of the mandible - elongates with age, could have thicker cortical bone, divergent roots

Question 36

what happens when we do a facial nerve block

Answer 36

this happens if we inject too deep, there is a risk of injecting into parotid gland, loss of IPSILATERAL tone in facial expression!!! - they are unable to blind therefore we need to cover the eye, would keep these pts KUO !

Question 37

What would we carry out if the IDB wasnt working due to the patients obscured anatomy?

Answer 37

using ARTICAINE (not lidocaine), placed bucccally, lingually or use one of the supplemental techniques

Question 38

describe the membrane expansion theory

Answer 38

LA diffuses into axon membrane and prevents Na channels opening!

Question 39

Uncharged LA what…

Answer 39

passes through the membrane easier!!!!!! IT IS LIPID SOLUBLE