Local Anesthesia 1 Flashcards
Nerve type classification
A, B, C and subtypes
A: large, myelinated
Alpha, beta, gamma = motor, proprioception
Delta = sensory
B: preganglionic autonomic (otherwise same as Aδ)
C: small, unmyelinated
Sodium channel activation gate:
Inactivation gate?
Act: m
Inact: h
Steps in impulse propagation
Na influx causes rapid depolarization
Na channels close, K permeability increases
Polarity restored
Wave of depolarization
_ is responsible for depolarization
Na channel inactivation
Distance b/t nodes is proportional to _+
Diameter
How does local anesthetic act on nerves
Blocks influence of stimulation on Na permeability
Specific receptor vs. membrane interaction theories
SR: anesthetic receptor in channel, from intracellular side
MI: agent molecules associated with hydrophobic membrane
_ is the common ester LA. Almost all other injectables are _
Procaine
Amides
Q is the _ constant
pKa is the _ constant
Aqueous distribution constant - ability to penetrate hydrophobic tissue
Dissociation constant - proportion of ionized to unionized molecules
Susceptibility to blockade
From most to least affected
DWCSTPP
Dull pain Warmth Cold Sharp pain Touch Pressure Proprioception
5 things in an anesthetic compound, common examples
Local anesthetic Vasoconstrictor Antioxidant (w VC) - Na metabisulfite Preservative - methylparaben PH adjusting agents - HCl,NaOH
Typical pH of anesthetic compound
4-6, especially with vasoconstrictor
Vascular uptake (systemic distribution) depends on what 3 things
Vascularity of area
Vasodilation of agents
Quantity
More lipophilic = _ % bound
Higher
Conditions that increase plasma binding (5)
Conditions that decrease plasma binding
MI, cancer, trauma, surgery, chronic pain
Pregnancy, oral contraceptive, estrogen, acidosis, increasing dose
How long does it take the following to uptake unbound drug:
Lungs
Brain, heart, liver, kidneys
Muscle
Fat
Lungs - 1 min
BHLK - 5 min
Muscle - 15 min
Fat - 1-2 hrs
_ breaks down ester anesthetics
Psudocholinesterase
CNS effects of lidocaine in low, moderate, mod/high, high conc.
Low: anticonvulsant, relaxation, analgesia
Mod: euphoria, drowsiness, slurred speech
Mod/High: disorientation, tremor, unconsciousness, seizures
High: coma, Resp arrest
High conc of anesthetic decrease what in the heart
Conduction velocity Automaticity Myocardial contractility Cardiac output Blood pressure
More _ an anesthetic is, the greater proportion of cardiovascular to CNS effects
Lipophilic
Adrenergic receptors: α1 α2 β1 β2
α1: increases BP
α2: inhibits NE release
β1: Increases HR
β2: Decreases BP
Plain LA are _ by nature
Vasodilator
3 reasons for vasoconstrictors in LA
- Hemostasis
- Lower toxicity by lowering CV absorption
- Increased duration
3 modes of action of VC
Direct - act on adrenergic receptors
Indirect - use NE release
Mixed - both
1:1000 conc. Means what
1gm of solute in 1000 ml of solvent
1,000 mg in 1,000 ml
How much epinephrine is in each of the following:
1: 50,000 1.7 ml cartridge
1: 100,000 1.7 ml c
1: 200,000 1.7 ml c
- 034 mg
- 017 mg
- 0085 mg
Maximum epinephrine dose per appointment for healthy person?
Pt. With cardiovascular disease?
Healthy: 0.2 mg
Diseased: 0.04 mg or 2 cartridges of 1:100,000 epinephrine
Antioxidant Most used with epinephrine
Sodium bisulfite
4 things that determine which vasoconstrictor to use
Length of dental procedure
Hemostasis requirements
Post-op pain control requirement
Medical status
An alpha blocker would cause what two effects
Hypotension and tachycardia
Non-selective β blocker would cause _
Increased blood pressure and bradycardia
If a patient is taking TCAs, what can epinephrine do? Why?
Produce exaggerated effects
TCAs block reuptake of NE and E
Epinephrine is metabolized by what two enzymes
MAO
COMT
5 contraindications to using VCs
ASA IV Acute MI Angina at rest (unstable angina) Cardiac dysrhythmias Uncontrolled hyperthyroidism
Avoid _ in patients with methemoglobinemia
Prilocaine
Local infiltration vs nerve block
LI: Tx in same area in which local an was deposited
NB: an. Deposited close to main nerve trunk, away from tx
What 6 factors determine selection of LA technique
- Area (bone differences)
- Procedure(s) performed
- Duration and profoundness needed
- Age
- Hemostasis
- Presence of infection
PSA and MSA innervate which teeth
MSA= premolars and MB root of first molar
PSA= molars except MB root of first molar
Which nerves innervate palatal mucoperiosteum
Anterior teeth: nasopalatine nerve
Premolars and molars: greater palatine
Supra-periosteal injection: Used for what Where Needle Contraindications
Pulpal anesthesia in maxillary teeth
Outside maxilla at level of root apex
25 or 27 gauge needle
CI for large areas
PSA block:
Injection site
Angulation
Height of MB fold over second molar
Up, in and back all at 45˚ angle
MSA block:
Point of insertion
Height of Mucobuccal fold above max 2nd premolar
Infraorbital block:
Which nerves are anesthetized
Point of infiltration
Depth and orientation of needle:
ASA, MSA, infraorbital nerve
Over max 1st premolar
Needle touches roof of foramen and bevel is towards foramen
Palatal anesthesia requires _
Topical and pressure anesthesia
Greater palatine nerve block: Which teeth Point of insertion Pressure where: Depth
PM and molars
Anterior to GP foramen
Pressure at junction of alveolar process and HP
5mm
Incisive nerve block:
Needle insertion:
Depth
Lateral to incisive papilla
5mm
V2 nerve block high tuberosity technique: Where Depth Amount Risk
Same as PSA
30mm
Deposit 1.8 ml
Risk of hematoma formation
V2 greater palatine approach
Where
Problems
Up through greater palatine foramen
Close to eye, can have vision problems
Volume of LA injected: infiltration: PSA MSA ASA IO Palatal infiltration Greater palatine Nasopalatine V2 nerve block
I: 0.6 PSA: 0.9-1.7 MSA: 0.9-1.2 ASA: 0.9-1.2 Palatal inf: 0.2-0.3 GP: 0.45-0.6 NP: 0.45 V2: all of it
IAN supplies:
Teeth to midline (24/25 cross over)
Body of mandible
Buccal mucoperiosteum, mucous membrane ant. To mand 1st molar
LB nerve supplies
Buccal mucoperiosteum of mandibular molars
Lingual nerve supplies
Ant. 2/3 of tongue and floor of mouth
Lingual mucoperiosteum
IAN block:
Height:
Depth:
Angle
Height:
Index finger in coronoid notch
6-10 mm above occlusal plane
Finger on coronoid
Lateral to pterygomandibular raphe
Tip located slightly superior to mandibular foramen
Depth:
To the BONE (20-25 mm, 2/3 to 3/4 of long needle)
From opposite premolar region
Lingual nerve block
From IAN, withdraw 5mm and inject 0.3 ml
Accessory mandibular innervation (mylohyoid nerve) block location
Lingual surface of tooth posterior to tooth in question
Long buccal n. Block:
Insertion
Angle
Depth
Mucous membrane distal and buccal to most distal molar in arch
Parallel and lateral to occlusal plane
Bone contact, 2-4 mm
Mental nerve block:
Affected tissue:
Needle insertion:
Muc membranes ant to mental foramen and skin of lower lip and chin
MB b/t apices of 1/2 premolars
Gow-Gates V3 block:
Insertion:
Target area
Depth
Distal to max 2nd molar
Target: lateral side of condylar neck, just below lat. pter muscle insertion
To BONE
vazirani ankinosi V3 block (closed mouth)
Who?
Why
Insertion
Pt with trismus
Relieve muscle spasm (V3 innervates muscles of mastication
Medial border of ramus at height of MGJ next to max 3rd molar
