local anaesthesia- difficulties and complications Flashcards
Is LA safe?
Yes
Average dentist- ~15 patients a day
So 70 mil a year receive LA
Major complications are v rare
What could go wrong?
Agitated patient- can’t cope so consider premed, sedation or GA
Poor technique- wrong place, too little (usually IAN) so repeated
Anatomical variation- eg zygomatic buttress over first molar roots
Alternative pathways of pulpal fibres- supply from lingual, buccal, mylohyoid, cervical plexus so infiltrate around tooth
Local infection- pH changes so less lipophilic component and high vascularity which disperses LA
Inability to place needle appropriately due to trismus/gagging
How can pain be reduced?
Make tissues taut
Inject slowly in tight tissues
Avoid a subperiosteal injection
Solution should be room temp
Never refill LA cartridges- in case wrong solution
Don’t penetrate nerve- ‘electric shock’
~prolonged impairment of sensation (~months)
(Usually IAN block- worse w articane and prilocaine so avoid)
~no treatment
How can equipment breakages be avoided?
Cartridge- due to misalignment of syringe or blocked needle
~usually plastic
~if glass for intraligamentary must have metal sheath
TEST AND INJECT SLOWLY
Needle- ~if occurs, remove w artery forceps ~if not, refer to oral surgeon (radiographs at 2 angles and removal under GA) ~keep all details and hub of needless NEVER BEND OR INSERT TO HUB
What happens if LA gets into the parotid gland?
Parotid (usually IAN)
~partial/complete facial nerve paralysis resolves after LA wears off
~protect eye if lids affected
What could happen if LA gets into a blood vessel?
Transported to eye/orbit OR diffusion from maxillary injection site
~visual loss/diplopia/squint resolves after LA wears off
Haematoma (usually posterior superior block)
~swells/bruises- monitor, exercise
~infected- could lead to severe trismus (medial pterygoid in IA block) so apply pressure, prophylactic antibiotics
Blanching (in an artery) due to vasoconstrictor
~up to half hour so reassure
Adrenaline transported centrally
~palpitations, drug toxicity, LA failure
What could go wrong later on after LA?
Self induced trauma-
~hot drinks/cigarettes on lip
~children biting
Needle track infection
~treat as any other infection
What should be considered for allergies?
Higher risk w esters and preservatives- but aren’t used anymore
Take careful history
Latex in cartridges sometimes
Gloves to avoid contact dermatitis
Delayed hypersensitivity (urticaria after 24hrs) Acute oedema (rapid swelling lips/eyelid/tongue) Anaphylaxis (bronchospasm, BP drop, collapse)
Sensitivity test (dermatology)
Antihistamine
0.5-1ml 1:1000 adrenaline sc/im
Hydrocortisone sodium succinate 100-300mg iv
What are the toxic effects of LA?
LA agent-
~could give intravascular or high dose to kids
~CNS (excitatory at low, depressant at high on heart)
~prilocaine can cause methaemoglobinaemia
Adrenaline-
~anxiety, trembling, headache, palpitations, sweating, dizziness
MAKE SURE TO ASPIRATE, INJECT SLOWLY, CORRECT DOSE
What should you do if toxicity occurs?
Stop Call for medical assistance Protect patient from injury Monitor vital signs Provide basic life support
What are the maximum recommended doses of LAs?
Lignocaine 2%- 4.4mg/kg
Prilocaine 3%- 6mg/kg
Prilocaine 4%- 6mg/kg
Articane 4%- 7mg/kg
What underlying cardiac problems might affect LA?
Cardiac disease/hypertension
~less LA due to adrenaline
~adrenaline- high excitability and high systolic but low diastolic BP
~maximum 2 cartridges
If unstable angina, recent MI or refractory arrythmias
~use prilociane or lignocaine/mepivacaine plain
Felypressin (w prilocaine) could cause coronary vasoconstriction
~maximum 3 cartridges
What drugs might affect LA?
Phenothiazines (anti psychotic)
~adrenaline could potentiate hypotension
~normal dose is fine
Tricyclic antidepressants (inhibit uptake of catecholamines so high intracerebral lvls and improved mood)
~reduces reuptake of adrenaline at nerve endings so increases its effect
~limit to 2 cartridges
Non-potassium sparing diuretics and calcium channel blockers (eg verapamil)
~adrenaline exacerbates decrease in potassium (hypokalaemia)
~limit to 2 cartridges
Beta blockers
~increases toxicity (reduces hepatic blood flow, inhibits liver enzymes, leads to BP increase by adrenaline)
~limit to 2 cartridges
Anti-Parkinson drugs (entacapone and tolcapone)
~affect metabolism of adrenaline
~limit to 1 cartridge
GA (halothane)
~increases sensitivity to adrenaline
~reduce maximum dose by 50%
Recreational drugs (past 24hrs) ~reduce/avoid LA agents
How might LA affect pregnancy?
Miniseries all drugs
Lignocaine/adrenaline ideal however
Bupivacaine- could cause maternal cardiac problems and foetal hypoxia
Felypressin- could cause uterine contractions and decrease in placental blood flow
Prilocaine- crosses placental barrier more than lignocaine
How should LA be considered if a patient has been exposed to irradiation to the mandible?
There’s reduced blood flow
So don’t use vasoconstrictors
Use lidocaine plain etc
