Local Anesthesia Flashcards
In the U.S. approximately___`% of the population avoid dental care due to fear
10
What are the desirable Properties for local anesthesia?
1) No Irritation to tissue
2) No permanent alteration
3) Low systemic toxicity
4) Effective if injected into tissue or mucous membranes 5) Short onset
6) Long of enough duration of action for the procedure
7) Potent yet not harmfully concentrated
8) Not elicit allergic reaction
9) Readily undergo biotransformation
10) Sterile or capable of being sterilized by heat without deterioration
____ ____ is the cornerstone of all anesthesia?
Local anesthesia
____ _____ Prevents generation and /
or conduction of a nerve
impulse
Local anesthesia
The least experience of pain which a subject can recognize
Pain threshold
The greatest level of pain which a subject is prepared to tolerate
Pain Tolerance
the __________ fluid is more positively charged.
extracellular fluid
The _________ fluid is more negatively charged
intracellular fluid
What are the five stages of Nerve Impulse Transmission?
- resting phase channel closed
- Fibre stimulated, channel opens sodium enters
- Cell depolarized, channel closes.
- Potassium exits down concentration and electrical gradients.
- Fibre repolarized Na/K pump restores balance.
Where do local anesthetics work ?
Nerve membrane is where local anesthesia
exert their pharmacological actions
– Local anesthesia binds to specific receptor on the
Na channel, preventing from opening.
Specific Receptor Theory
__ Fiber conducts pain signals?
C fiber
Which fibers are faster A delta and Alpha OR C fibers
A alpha and delta
_____ ____ insulates axons electrically
and pharmacologically
Myelin sheath
Where are sodium channels most abundant?
Nodes of ranvier
- nodes needs to be blocked and - mm length needed to ensure effective anesthesia
2-3 nodes
8-10 mm
How does local anesthesia work?
- Decrease permeability of ion channels to Na
• Nerve block by local anesthesia is a
Non-depolarizing block
majority form of local anesthesia are _______ ______.
tertiary amine
What two Local anesthetics are 2ndary amines?
prilocaine and hexylcaine
t/f: All local anesthetics are amphipathic
except…benzocaine
true
Antihistamine and anticholinergics have______
local anesthetic properties
weak
What are the two types of Local anesthetics?
Amides and esters
Resist hydrolysis, excrete unchanged in urine
amide
Readily hydrolyzed in aqueous solution
ester
All of the following are examples of \_\_\_\_\_\_\_: – Procaine – Propoxycaine – Tetracaine – Cocaine – Benzocaine – Dyclonine
Esters
All of the following are examples of \_\_\_\_\_\_\_: – Lidocaine – Etidocaine – Mepivacaine – Bupivacaine – Prilocaine – Articaine
Amides
______ doesn’t have hydrophilic group Therefore, its not suitable for injection but nice topical !!
Benzocaine
Local Anesthesia combine with acids to form local anesthetic salt (HCl). This makes them ______ basic compunds
WEAK
dissociation constant
pKa
Relative proportion of ionic form depends on_____.
pKa
t/F: When pH of solution = pKa, you have 50/50 RN/RNH+
true
What two Factors are involved in the action of local anesthesia
1) Diffusion through nerve sheath
2) Binding at receptor site
______ ____ is able to freely diffuse across the neuron axon membrane and into the axoplasm.
free base
t/F; Once in the axoplasm, the free base is then changed back into the ionized form and the process continues until all of the anesthetic is in the axoplasm.
true
t/f: increased translates to slow onset because few free base molecule available to diffuse
true
decreased pKa will have_____ onset
faster
_______ pH determines the ease for nerve blockade
Extracellular
Inflamed or infected tissue is much more difficult to get
adequate anesthesia b/c _____ or ______
lower pH or ↑H+
t/f: Keep low pH equates ↑effective shelf live of local anesthesia
true
Most local anesthesia have pH ____ to ___
5.5 to 7
from the innermost to the outermost, what is the composition of peripheral nerve
Endoneurium –> Perineurium —> Epinerium
_______ is greatest barrier for diffusion because Slower diffusion is dependent on the thickness
Perineurium
______ fiber tends to innervate proximal region (molars)
Mantle
______ fiber innervates more distal points (incisors)
Core
Complete conduction blockade requires ______ and ______.
Volume and Concentration.
What happen to injected drug?
– Absorbed by nonneural tissue
– Diluted by interstitial fluid
– Removed by capillaries and lymphatic system
– For Ester-type: immediate enzymatic hydrolysis
_____ pKa posses rapid onset of action
Lower
t/f: Greater lipid solubility relates to intrinsic potency because the nerve membrane is 90% lipid.
true
t/f: Increased protein binding will increase duration because nerve membrane is 10% protein.
true
the result of the following is?
– “reverse” of anesthetic induction pattern
– Intraneural concentration exceeds extraneural concentration
recovery from nerve block.
Recurrence of Immediate profound anesthesia results in what two things?
– Reduced concentration at mantle fibers
– Residual local + newly deposited supply =
immediate profound anesthesia
– ↑ Tolerance to drug after repeated administration
Tachyphylaxis
What factors can increase the tolerance to drug after repeated administration?
– Edema – Localized hemorrhage – Clot formation – Transudation – Hypernatremia – ↓pH of the tissue
t/f: lipid solubility influences potency.
true
t/f: pKa influences onset
true
t/f: protein binding influences duration
true
