Local Anesthesia Flashcards
Which nerves are anesthetized with a Gow-Gates injection?
- Auriculotemporal
- Inferior alveolar
- Buccal
- Mental
- Incisif
- Lingual
- Mylohyoid
Which structures/tissues are anesthetized following a Gow-Gates injection?
Ipsilateral teeth up to the midline, buccal and lingual tissues, anterior two thirds of the tongue, floor of the month, skin over the zygoma, posterior aspect of the cheek and temporal region.
Which structure secretes epinephrine?
Adrenal medulla
Describe epinephrine action?
Sympathomimetic
Acts on adrenergic receptors alpha and beta
A1: vasoconstrictor (primary receptor in oral mucosa)
B1: vasopressor (contractibility) and increase heart rate
B2: vasodilatation in skeletal muscle (very little in oral mucosa)
Reduce pulpal blood flow (Kim)
Can induce BP drop and increase HR (5-10 min)
When given with LA, reduces peak plasma and control hemorrhage.
Name condition for which epinephrine is absolutely contraindicated.
Heart diseases: - unstable angina - recent myocardial infarction - recent coronary artery bypass surgery - refractory arrhythmias - untreated and uncontrolled severe hypertension - untreated and uncontrolled congestive heart failure Uncontrolled hyperthyroidism Uncontrolled diabetes Intolerance to sulfites Steroid-dependent asthma Pheocromocytoma
Perusse 1992
Hyperthyroidism symptoms
Tachycardia Goiter Palpitation Nervousness Tremor Increase of the BP heat intolerance
Perusse 1992
How much epi in one cartridge of 4% lidocaine 1:100 000?
0.018 mg
How much epi given IM for an anaphylactic choc?
0.3-0.5 mg
Diabetic patient: what to consider for local anesthesia/hemorrhage control?
If diabetes isn’t well controlled, epi is contraindicated because epi is a hyperglycemic hormone.
If the diabetes is well controlled (with insulin, hypoglycemic medication or diet): dose of epi needed as small as possible
Asthmatic patient: what to consider before local anesthesia?
If severe asthma, corticosteroid dependent: avoid epinephrine because higher risk of sulfite sensitivity. 8.4% vs 0.8% (asthmatic non corticosteroid dependent pts) (Bush).
Consequence: severe asthmatic reaction
Name relative contraindications of epinephrine.
Patient taking tricyclic antidepressants
Patient taking phenothiazine compounds (anti-psychotic)
Patient taking monoamine oxidase inhibitors
Patient taking nonselective beta-blockers
Cocaine abusers
Describe the mechanism of action of lidocaine.
Lidocaine blocks fast voltage-gated sodium channel in the cell membrane of post synaptic neurons, preventing depolarization and inhibiting the generation and propagation or nerve impulses.
True/false
Lidocaine has anti-inflammatory and immunomodulating properties.
True
How lidocaine is eliminated?
Metabolized in the liver and excreted by the kidneys in urine (10% as an unchanged drug and 90% as metabolites)
What is the maximal dosage of the different L.A?
Lido 2% 1:50 00 or 1:100 00
7.0mg/kg
500mg/kg
Lido 2% plain
4.4mg/kg
Max 300 mg
36 mg/cartridge
Mepivacaine 3%
6.6 mg/kg
Max 300 mg
54 mg/cartridge
Articaine 4% 1:100 000
7.0 mg/kg
Max 500 mg
72 mg/cartridge
Describe CNS and CVS symptoms of L.A toxicity/overdose.
CNS - initially excitation, after drowsiness, seizure, disorientation, loss of consciousness
CVS - decreases cardiac output, hypotension, cardiac arrest
Which L.A is more susceptible to cause methemoglobinemia?
Prilocaine
Lack of oxygen in RBC
What the best L.A to use for a patient with severe liver dysfunction?
Procaine
An ester metabolisms by serum esterases so toxicity in those with liver is not a problem.
Symptoms of a vasoconstrictor overdose.
Anxiety Headache Palpitation dizziness Nausea Stomach ache Restlessness Tremor Anginal pain Hypertension Tachycardia
5 reasons of anesthetic failure.
1- Lower pH of inflamed tissue reduces the amount of base form of anesthetic.
2- unsuccessful technique
3- Inflamed nerves have altered resting potential and decreased excitability threshold
4- TTX (tetrodotoxines produce by bacterias) resistant sodium channel
4- apprehensive patient have decrease pain threshold
What is the concentration of epi in mg/ml for L.A with 1:200 000, 1:100 000 ant 1:50 000 epi?
1: 200 000 = 0.005mg/ml
1: 100 000= 0.010mg/ml
1: 50 000= 0.02mg/ml
Which teeth are anesthetized with an anterior superior nerve block?
- Max central inc
- Max lateral inc
- Canine
- when MSA absent: first and second max pre-molar and MB root of the max first molar
What are done landmarks to adequately perform an anterior superior nerve block?
First max pm aligned with infra-orbital foramen
Half long needle in
Which teeth are anesthetized with a middle alveolar nerve block?
- Max second molar
- Max first molar
- Mb root first molar (if not inerved by PSA or ASA
What is the main landmark for a middle alveolar nerve block?
Vestibule second pre-molar
Which injections are associated with trismus?
PSA nerve block
IANB
Give 2 risks associated with a posterior alveolar nerve block.
- Hematoma formation from injection of L.A in the pterygoid plexus of veins
- Accidental puncture of the maxillary artery
To avoid those risks: aspiration and adequate landmarks
Which teeth are anaesthetized with a PSA nerve block?
third, second and first max molars despite MB root of the first molar
What is the Finder and Moore rule (2002)?
1 cartridge of L.A for every 25 pounds of the patient weight.
Name 5 possible complication of L.A.
- Cardiovascular effects: tachycardia, increase of the heart rate and BP (adrenergic receptors)
- Systemic effect: Initially excitatory phase (ms contraction, grand mal convulsion, tremor), followed by a depressive phase (sedation, hypotension, respiratory arrest)
- Peripheral nerve paresthesia: 5X more w/ articaine than lido after IANB
- L.A. or Latex allergy: very rare, maybe because of the latex stopper
- Sulphite allergy: Sulfites are added for epic stability (to avoir molecule breakdown). Asthmatics 5% more frequent.
2 principal causes of trismus?
1- insertion of the needle in the pterygoid plexus
2- laceration/puncture of a small vein
This can cause a larger hematoma in the infra temporal fossa
Multiple injections increase the chance of bleeding from muscles or blood tissue damage
Trauma to muscles or blood vessels in the infra temporal space is the most common etiology factor in trismus
Infection of the latter hematoma further contributes to hypomobility
Maximum dose epi for cardiac people?
0,04 mg
Malamed
Best L.A for pregnant pt?
Lido and prilocaine
FDA B
According to each ASA categories, what is the Max dose of epinephrine?
ASA 1- 0.2 mg
ASA 2 - 0.1 mg
ASA 3 - 0.04 mg
Through which structures the needle goes through for an IANB?
a. Soft tissue
b. Posterior aspect of the buccinator
c. Lateral to the medial pterygoid muscle, lingual of lingual nerve
d. Through the lateral pterygoid
e. Injection of L.A. in the pterygomandibular space
