Local Anaesthetic Flashcards by Alistair Stoddart

What is the structure of a LA molecule

Aromatic region (Hydrophobic)
Ester or Amide bond
Basic amine side chains (hydrophillic)

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What is a LA molecule presented as and why

Hydrochloride to render the amine base more soluble making the injection less painful

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Why is the LA molecule partly dissociated

Its active in its ionised form but can only cross the membrane in it unionised form

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What is the composition of a LA preparation

LA base present as a hydrochloride
2-4% solution for dental use
Reducing agent
preservatives 
vasoconstrictor e.g. adrenaline

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What are the 2 familys of LA

Esters and Amides

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What are the most likely causes of an alergic reaction to LA

The rubber bung or preservatives in the LA

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What are esters and amides broken down by

Esters- tissue esterases

Amides- liver amidases

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What does a preperation of lignocaine consist of

2% lignocaine HCL or 2% lignocaine HCL + 1:80,000

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What does a preperation of Prilocaine consist of

3% prilocaine HCL or 3% prilocaine + felypressin

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What is the max dose of adrenaline

500ug

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How much adrenaline does a cartridge contain

27.5ug

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In the dental school what syringe is used

safety plus

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What is the most fragile part of the needle

The hub

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How do you asemble a syringe

1A- Colllect syringe handle and needle
1B- Collect selected LA cartridges (check batch no. and exp. date)

2A- Unpack everything
2B- record details for decontamination

3- Make up syringe handle, attach rubber bung so that the wider side faces towards the handle

4- Load cartridge of LA solution in the needle barrel, gold side in first

5- Connect syringe handle and LA needle with cartridge, should hear a click into place and then check for attachement

6- Prepare needle for use, pull back on safety sheath with needle away from you and sheath should click into place at connection between syringe and barrel. Make needle safe by re-sheathing with 1 click= safe but can be reused 2nd= needle locked

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Why use LA

Undertake a range of dental procedures pain free

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How do you prep a patient before LA

Check med history
Position in chair
Dry mucosa
Apply topical for 1-2mins

What is the infiltration technique

LA solution deposited around terminal branches of nerve

What is the block technique

LA solution deposited beside nerve trunk

How would you achieve anaesthesia of dental pulp in the maxilla

Buccal Infiltration

How would you achieve anaesthesia of buccal gingivae in the maxilla

Buccal Infiltration

How would you achieve anaesthesia of palatal gingivae

Palatal injection

How would you achieve anaesthesia of dental pulp in the mandible

Lower molars (and second premolar)- Inferior alveolar nerve block (IAN/IDB)

Lower premolars and canine-Mental (incisive) nerve block

Lower canine and incisors- Buccal/labial infiltration

How would you achieve anaesthesia of buccal gingivae in the mandible

Lower molars and second premolar- (Long) Buccal infiltration

Lower first premolar and canine- Infiltration or long buccal or mental nerve block

Lower incisors and canines- Buccal/labial infiltration

How would you achieve anaesthesia of lingual gingivae in the mandible

Secondary part of a IAN or lingual infiltration

What is the best technique when injecting LA

``` Strech mucosa Puncture mucosa quickly Position needle tip at target point Bevel of needle towards bone ASPIRATE Inject SLOWLY ```

What is the method for a Buccal infiltration

Stretch Cheek Puncture mucosa with correct bevel distal of the tooth Advance needle till over apex of tooth If contact bone withdraw slightly Aspirate Remove syringe from mouth Slide sheath down to first click Can replace cartridge if need further injections Wait for 2 minutes for anaesthesia and test

What is the method for a palatal infiltration

Short needle Area of needle penetration is 5-10mm palatal to center of the crown Apply presssure directly behind injection site with a cotton probe or mirror handle Insert needle at 45degrees to injection site with bevel angled towards soft tissue While maintaining pressure behind the injection site, advance the needle, and slowly deposit anesthetic solution as the soft tissue is penetrated Advance the needle until contact is made with bone Depth of penetration is usually no more than a few millimeters. The tissue is very firmly adherent to the underlying periosteum in this region, causing resistance to the deposition of local anesthetic No more than 0.2–0.4 mL of anesthetic solution is necessary to provide adequate palatal anesthesia Blanching of the tissue at the injection site immediately follows deposition of local anesthetic

what LA injections can be perfromed as buccal infiltrations in mandible

Mental nerve block- between apices of lower premolars ( do not put in foramen) Buccal injection- Lower buccal gingivae

What is the method for Inferior Alveolar block

Long needle Identify site so ask patient to open wide so can identify landmarks Place thumb of nonworking hand intraorally at the coronoid notch and fingers extraorally at posterior border of ramus inserted through the mucosa in the mandibular retro-molar region and lateral to the the pterygomandibular raphe 6-10mm above molar Syringe lies over contra lateral 5-6 Advance to bony contact (1cm of needle visible) If no bony contact reposition syringe distally and if too soon reposition mesially When in correct position withdraw from bony contact slighlty Aspirate and inject slowly (about 1.5ml)

What is the onset time of Lidocaine

2-3mins

What does a preperation of Articane consist of

Articane HCL 4% with adrenaline of either; 1:100,000 1:200,000 1:400,000

What is the difference between Articane and Lidocaine

Articane is more potent by about 1.5x and has a more rapid onset

What are the systemic complications of LA

``` Psychogenic Interactions with other drugs Cross infections Allergy Collapase Toxcicity ```

What drugs can LA interact with

Tricyclics, B blockers, Non-potassium sparing diuretics

What is the max dose (mg/kg) of Lignocaine

5mg/kg

What is the max dose (mg/kg) of Articane

7mg/kg

What is the max dose (mg/kg) of Prilocaine

8mg/kg

With patients with cardiovascular disease what is the recomended number of cartridges

<3x2.2ml cartridges

What are the local complications of LA

Failure to achieve anaesthesia Prolonged anaesthesia(direct trauma from needle) Pain after/during injection Trismus(PROBABLY DAMAGE TO MEDIAL PTERYGOID) Haematoma Broken needle Infection/ contamination Facial paralysis (local into protid gland) Intra-vascular injection