LA difficulties and complications

Question 1

Is LA safe?

Answer 1

Extremely safe - average dentist gives approx 15 patients LA per day
=1/4 million/ day
=approx 70 million/year in UK
Major complications very rare

Question 2

Failure to obtain anaesthesia: agitated patient

Answer 2

Has it failed? Is px feeling pain or pressure

Consider premedication, sedation or GA

Question 3

Failure obtain anaesthesia: faulty technique

Answer 3

Wrong place, too small a volume (usually IAN), therefore repeat

Question 4

Failure to obtain anaesthesia: anatomical variations

Answer 4

Zygomatic buttress over first molar roots

Question 5

Failure to obtain anaesthesia: alternative pathways of pulpal fibres

Answer 5

Supply from lingual, buccal, mylohyoid, cervical plexus, therefore infiltrates around tooth

Question 6

Failure to obtain anaesthesia

Answer 6

Agitated px
Faulty technique
Anatomical variation
Alternative pathways of pulpal fibres
Inability to place needle appropriately
Local infection

Question 7

Failure to obtain anaesthesia: inability to place needle appropriately

Answer 7

Trismus
Unwillingness of px
Gagging

Question 8

Failure to obtain anaesthesia: local infection

Answer 8

pH changes (but only small so may not be cause) reduced lipophilic component
> vascularity, LA dispersed
Receptor or neural pathway sensitisation?
Why significant with regional block?
Therefore inject remote from site - avoid spread

Question 9

Pain during injection

Answer 9

Tissues not taut
Excessive p in tight tissues
Subperiosteal injection
Solution cold - use at room T
Wrong solution - never refill LA cartridges
Penetration of nerve = 'electric shock'

Question 10

Penetration of nerve

Answer 10

‘electric shock’
‘anaesthesia did not wear off’
Prolonged (usually partial) impairment of sensation
-worse with articaine 4% and prilocaine 3% therefore given as IAN blocks
Recovery dependent upon degree of injury, usually <3 months
No treatment

Question 11

Cartridge breakage

Answer 11

Rare, due to misalignment of syringe or blocked needle (always test and inject slowly)
Beware glass (usually plastic sleeved, or plastic cartridges)
Use sleeved glass cartridges for intraligamentary injections

Question 12

Needle breakage

Answer 12

Rare (do not insert to hub)
At site of bending, metal fault or hub
Remove immediately with artery forceps
If not possible, refer to oral surgeon for removal under GA (or may move in tissues, cause pain, trismus and worry)
Radiographs at 2 angles and localising needles
Keep all details and hub of needle

Question 13

Facial nerve paralysis

Answer 13

LA within parotid
May be partial or complete, resolves after LA wears off
Protect eye if lids affected

Question 14

Visual disturbance

Answer 14

Very rare - visual loss/ diplopia/ squint
Due to intravascular LA to eye/orbit or diffusion from maxillary injection site
Recovery after LA wears off

Question 15

Vascular problems

Answer 15

Aspiration suggests entry into vessel in 2-12% of injections
If positive aspiration, reposition needle
Haematoma
Blanching at distant site
Intravascular injection (greater potential for drug toxicity - see below, LA failure)

Question 16

Haematoma

Answer 16

Dependent upon site - posteriorsuperior dental worst
Results in:
-swelling and subsequent bruising
-possibly trismus if in medial pterygoid (IA block)
-may become infected, leading to severe trismus

Question 17

Haematoma treatment

Answer 17

Pressure
Prophylactic antibiotics
Trismus slowly resolves
If not infected, exercises

Question 18

Blanching at distant site

Answer 18

Due to intra-arterial vasoconstrictor or effect of needle on vessel
May be up to half-hour, reassure

Question 19

Self-induced trauma

Answer 19

Hot drinks/ cig on lip

Biting (children)

Question 20

Needle track infection

Answer 20

Very rare with sterile disposable needles in absense of haematoma
Treat as for any other infection

Question 21

Allergy

Answer 21

Higher incidence with procaine/ amethocaine (esters)
Take careful history
Allergen usually preservative but most LA now preservative free
Care with latex allergy (latex in cartridges)
Responses range: delayed hypersensitivity, acute oedoma, anaphylaxis

Question 22

Treatment of allergy

Answer 22

Dependent on severity
Antihistamines
Adrenaline
Hydrocortisone sodium succinate
Can refer to sensitivity tests
If negative undertake test infiltration

Question 23

Allergy: contact dermatitis

Answer 23

Dentist/ nurse - most likely with procaine/ amethocaine/ benzocaine (esters)
Avoid agent and wear gloves

Question 24

Toxicity of LA agent

Answer 24

Potential risk with inappropriately high dose, particularly with accidental intravascular injection or in small children
Most likely to affect CNS – excitatory at low doses, depressant at high doses
Depressant action on the heart
Prilocaine can cause methaemoglobinaemia (reduces RBC oxygen carrying capacity)

Question 25

Toxic effects of adrenaline

Answer 25

Adrenaline in LA can have systemic effects (see earlier lecture) Inappropriately high, toxic levels would lead to anxiety, trembling, headache, palpitations, sweating, dizziness (very similar to vaso-vagal syncope)

Question 26

Prevention of toxic effects

Answer 26

Aspiration Slow injection Dose limitation – should have no problems with correct doses

Question 27

Treatment of toxicity

Answer 27

``` Stop dental treatment Call for medical assistance Protect the patient from injury Monitor vital signs Provide basic life support ```

Question 28

Max recommended dose - lignocaine

Answer 28

Lignocaine 4.4mg/kg – healthy patient 2% lignocaine will contain 20mg/ml 65kg man may have a total of 65x4.4mg =286mg ~ 14.3ml of 2% ~ 6.5 X 2.2ml cartridges One tenth of a cartridge per kg in weight

Question 29

Cardiac disease/hypertension

Answer 29

Adrenaline increases force and rate of contraction of heart, increases cardiac excitability and ↑ systolic but ↓ diastolic blood pressure Minimal effects with normal LA doses Effects equivalent to normal endogenous level of adrenaline with light work Anxiety produces significant cardiac problems, so therefore use most effective LA – Lignocaine/adrenaline is ‘gold standard’ Sensible to limit to a maximum of two cartridges In case of unstable angina, recent myocardial infarct or refractory arrythmias, adrenaline is best avoided – use prilocaine or lignocaine plain Felypressin (with Prilocaine) may cause coronary vasoconstriction, so also restricted to three cartridges

Question 30

Patients taking other drugs

Answer 30

Monoamine-oxidase inhibitors (MAOIs): do not affect metabolism of exogenous catecholamines, therefore no effect Tricyclic antidepressants: inhibit uptake of catecholamines, leading to ↑ intracerebral levels and improved mood - No clinical evidence of adverse reactions with amount of adrenaline in LA - May be wise to limit to two cartridges Phenothiazines: (anti-psychotic) Non-potassium sparing diuretics

Question 31

Phenothiazines

Answer 31

(anti-psychotic) - Adrenaline could potentiate hypotension - No problem with normal dose range

Question 32

Non-potassium sparing diuretics

Answer 32

adrenaline exacerbates decrease in circulating potassium, so wise to limit to two cartridges

Question 33

Calcium channel blockers (e.g. verapamil)

Answer 33

increase the adrenaline induced hypokalaemia; increases toxicity – limit to two cartridges

Question 34

Anti-Parkinson drugs

Answer 34

the drugs entacapone and tolcapone affect the metabolism of adrenaline – limit to one cartridge

Question 35

General anaesthesia (Halothane)

Answer 35

increases sensitivity to adrenaline – therefore reduce maximum dose by 50%

Question 36

Recreational drugs within the past 24 hours

Answer 36

reduce the amount, or avoid, local anaesthetic agents

Question 37

Beta-blockers

Answer 37

increase the toxicity by reducing hepatic blood flow and inhibiting liver enzymes; may also lead to unopposed increase in systemic BP by adrenaline. Limit to two cartridges

Question 38

Tricyclic antidepressants

Answer 38

reduces reuptake of adrenaline at nerve endings, increase effect of adrenaline (little evidence) – limit to two cartridges

Question 39

Pregnancy

Answer 39

Minimise all drugs during pregnancy Bupivacaine should be avoided as it causes more maternal cardiac problems and foetal hypoxia in animal models Felypressin theoretically could lead to uterine contraction and a decrease in placental blood flow Prilocaine crosses placental barrier more readily than lignocaine Lignocaine/adrenaline is the LA of choice

Question 40

Liver disease

Answer 40

Reduce dose of amide LAs

Question 41

Irradiation

Answer 41

Caution using vasoconstrictors in an area that has previously been irradiated

Question 42

Bleeding diatheses

Answer 42

Avoid IAN blocks

Question 43

Pseudocholinesterase deficiency

Answer 43

Avoid ester local anaesthetic agents

Question 44

Phaeochromocytoma

Answer 44

Catecholamine producing tumour – avoid adrenaline

Question 45

Susceptibility to endocarditis

Answer 45

Avoid intraligamentary injections

Question 46

Methaemoglobinaemia

Answer 46

Prilocaine – conversion of haemoglobin to methaemaglobin – may cause cyanosis