LA Symposium Flashcards
How do local anaesthetics work?
LAs stop nerve conduction by blocking Na+ channels
- prevention of Na+ influx
- action potential generation and propagation blocked
Describe the structure of A nerve fibres:
Myelinated
Describe the structure of C nerve fibres:
Unmyelinated
What nerve fibres are found in the dental pulp?
Mostly unmyelinated C fibres
What are examples of Amide local anaesthetics?
- lidocaine
- prilocaine
- articaine
Give an example of an ester local anaesthetic:
Benzocaine (topical LA)
Why do most LA preparations include a vasoconstrictor agent?
LA itself is a vasodilator
- without vasoconstrictor the LA washes out of tissues quicker, leading to shorter usage time
What vasoconstrictor agents are typically found in LAs?
- adrenaline
- felypressin
Give examples of preservatives commonly used in LA solutions:
- Bisulphite
- Propylparaben
- people with “LA allergy” tend to actually be allergic to these preservatives opposed to the LA itself
Describe the difference between infiltration and block LA techniques:
Infiltrations:
- LA deposited around terminal branches of nerves
- can produce pulpal anaesthesia where bone is thin
- useful for maxilla & lower anteriors
Blocks:
- LA deposited beside the nerve trunk
- abolishes sensation distal to site
- used where bone too thick to allow infiltration eg mandible
What length of needle is used for IDB?
35mm
What are the important landmarks to note when performing an IDB?
- pterygomandibular raphe
- lower contralateral premolars
- 0.5 - 1cm above occlusal plane
Describe the “chasing anaesthesia” technique:
- give buccal infil & allow to work
- inject into interdental papillae
- slowly advance needle through interdental papillae until palatal tissues blanch
- inject into blanched palatal area
Give some alternative IAN block techniques:
- Gow Gates
- Akinosi technique
What are some systemic complications associated with LA use?
- fainting
- palpitations
- trembling
- allergy
- interaction with other drugs
- collapse
- toxicity
What drugs interact with dental LAs?
- MAOIs
- TCAs (tricyclic antidepressants)
- Beta blockers (limit quantity)
What are signs of local anaesthetic toxicity?
- convulsions
- loss of consciousness
- respiratory depression
- circulatory collapse
What are examples of local complications of LAs?
- prolonged anaesthesia
- trismus
- intravascular injection
- pain
- broken needle
- infection
You have given an IDB to a pt during dental treatment, they come back a few days later complaining of restricted mouth opening. What has likely happened? What can you do?
Damage to medial pterygoid during IDB
- injection too low
- injection too forceful/rapid
Management:
- reassure patient
- suggest usage of muscle relaxant or anti-inflammatory
You have just given an IDB to a pt as part of dental treatment, soon after the patients face becomes paralysed. What has likely happened? What should you do?
IDB likely deposited into parotid gland (injection too far posterior)
Management:
- test if pt can raise their eyebrows/crinkle forehead & lift their arm to rule out stroke
- reassure pt if suspected facial palsy
- cover eye with patch until blink reflex returns
You have just given a pt an IDB as part of dental treatment, suddenly the patient starts acting very anxious, looks pale and is clutching their chest. What has likely happened? What should you do?
IDB has been injected intravascularly
- reassure patient that it will pass very soon
- monitor patient incase symptoms worsen
- monitor pt for suspect myocardial infarction
You are administering LA to a patient and accidentally give yourself a sharps injury, what should you do?
- stop procedure immediately and inform patient
- make sharp safe
- take gloves off
- encourage wound to bleed
- run under water & wash with soap
- alert supervising clinician
- risk assessment with pt
- alert occupational health for bloods
- datix
