Local anesthetics Flashcards
1
Q
introduced cocaine as the first local anesthetic in 1884, for use in ophthalmology.
A
koller
2
Q
negative resting membrane potential
A
-70 - -90
3
Q
essential for anesthetic activity
A
lipophilic aromatic ring
4
Q
-CO-
A
ester
5
Q
-NHC-
A
amide
6
Q
membrane potential
A
20 mV or 35 mV
7
Q
Where do local anesthetics bind to
A
Alpha subunit
8
Q
Guarded receptor theory
A
-LA preferentially binds to both open or inactivated states
-Not to closed state
9
Q
The IONIZED fraction binds to the receptor on the cell inside or outside of the cell?
A
inside of the cell
10
Q
Name the Esters
A
Procaine
Chloroprocaine
Tetracocaine
Cocacine
Benzocaine
11
Q
Name the Amides
A
Lidocaine
Mepiviapine
Prilocaine
Bupivicaine
Ropivacaine
Articaine
12
Q
Nerve fiber sensitivity & DIFFERENTIAL BLOCKADE
A
B fibers > C fibers > small A > large A
13
Q
prophylactic measure to prevent bradycardia and hypotension with locals
A
Phenylephrine gtt
14
Q
a fibers
A
Alpha
Beta
Gamme
Delta
15
Q
A fiber with the largest diameter and fastest conduction and most heavily myelinated
A
alpha
16
Q
requires highest concentration of LA to be blocked
A
Alpha A Fibers
17
Q
fiber responsible for motor and proprioception
A
alpha A fiber
18
Q
a fiber that motor function, touch, pressure
A
Beta A fiber
19
Q
conduction velocity second to alpha a
A
beta a
20
Q
A fiber responsible for reflexes and innervate muscle spindles
A
Gamma
21
Q
a fiber responsible for reflexes
A
gamma
22
Q
a fiber that has a small diameter and slower conduction (30m/s)
A
a delta
Lamina I and V
23
Q
responsible for pain and temperative
A
a delta
24
Q
Fibers constitute the preganglionic autonomic nerves
A
B fibers
25
Similar diameter to A-delta, slow and less myelinated
B fibers
26
smallest fibers of all
c fibers
27
conducts pain and temperature
c fibers
28
only fibers unmyelinated and smallest of all fibers (<2m/second)
C fibers
Lamine 1 and 2
29
1/100,000 =
10mcg/ml
30
2% lido =
20mg/ml
31
Acidosis in the environment into which the LA is injected ....
increases the ionized fraction of drug
32
Absorption of drugs
(If teddy interrupts ice cream, everyone be super still)
Intravenous
Tracheal
Interpleural
Intercostal
Caudal
Epidural
Brachial plexus
sciatric-femoral
Subcutaneous
33
systemic toxicity is inversely proportional to
rate of hydrolysis
34
Vasodilation increases drug absorption and may cause ____.
toxicity
35
Most LA except ____ produce relaxation of vascular smooth muscle
cocaine
36
where is cocaine (an ester) metabolized?
plasma and LIVER cholinesterases
37
MAX DOSE OF COCAINE
5 mL of 4% solution
or
200 mg should be used
38
4%
4g/100ml
4000mg/100ml
40mg/ml cocaine
200mg = 5mL
39
DOA of LA is dependent on
protein binding
lipid solubility
40
DOA is directly proportional to
protien binding
41
Weak bases bind primarily to
alpha one acid glycoprotein
42
The onset of action depends on
State of ionization #1
Lipid solubility
Chemical structure
43
potency =
lipid solublity
44
high lipid solubility =
toxicity
45
DOA is directly proportional to
protein binding
46
Pseudochilinesterase deficiency=
Choose amide anesthetic
47
The rate of hydrolysis varies:
Alphabetical
Chloroprocaine = most rapid
Procaine = intermediate
Tetracaine = slowest
48
sunscreen allergy
avoid esters
especially procaine
Paraaminobenzoic acid may be an antigen responsible for allergic reactions
49
how does spinal anesthesia work in metabolism ?
needs to go into blood stream
50
how is lido broken down
oxidative dealkylation in the liver followed by hydrolysis to metabolite
51
prilocaine metabolite
converts hemoglobin to methemoglobin
52
treatment for methemoglobinemia
methylene blue
1-2 mg/kg
53
Cyanosis with decreased oxygen-carrying capacity
methoglobinemia
left shift
54
lidocaine metabolite protects against
protects against cardiac dysrhytmias
55
Drugs that cause methoglobinemia
prilocaine (EMLA)
BENZOcaine (Cetacaine, hurricane)
56
20% benzocaine spray delivers
200 - 300 mg for awakes, endo, TEE, bronchs
57
treatment for methemoglobinemia
Methylene blue
1 to 2 mg/kg IV over 3 to 10 minutes
** can repeat **
58
metHB levels >70%
transfusion
dialysis
59
Modulates the local from burning and speeds onset
Sodium bicarbonate
60
MOA of adding bicarb
increases pH of LA resulting in more drug in the nonionized state-readily able to diffuse across membranes
61
epi 1:200,000
5 mcg/ml
1g in 200,000ml
1000 mg /200,000 ml
1mg / 200 ml
1000 mcg / 200 ml
5 mcg/ml
62
avoid epi in area of
terminal circulation -->
fingers, toes, nears, nose
Hx of
CAD
HTN
arrythmia
uteroplacental insufficiecy
63
A2 agonists + LA
100mcg clonidine prolongs LA by 100m
Dex prolongs
64
prolongs DOA of LA
epinephrine
dexamethosone
dextran
clonidine?
dexmede?
65
provides supplemental anesthesia
clonidine
epinephrine
opiods (neuralaxial)
66
shortens onset time
bicarb
67
improves diffusion through tissues
hyaluronidase
68
Increases pH so more local anesthetics exist in nonionized state
sodium bicrab
69
1:200,000 =
70
are associated with a greater incidence of allergic reactions than the use of amides
Ester local anesthetics
71
What phase on the cardiac action potential is impacted by locals?
phase 0
(Na channel blockers)
72
Iv injection may result in hypotension, cardiac dysrhythmias, and AV block
bupivacaine
73
lipid dosing
An initial bolus of 1.5 mL/kg 20% lipid emulsion
0.25 mL/kg per minute of infusion -10 minutes after circulatory stability is attained
74
emla
5% lidocaine–prilocaine cream
75
1 to 2 g of EMLA cream are applied per
a 10 cm2 area of skin
76
calculate epi 1:100,000
1 gram/100,000mL
1,000mg/100,000mL
1mg/100 mL
0.01mg/mL
10mcg/ml
77
78
2% Lidocaine
% means parts per hundred
2 grams per cent (100)
2000mg/100 mL
20mg/ mL
79
How many mL of 2% Lidocaine can I give to an 80kg pt?”
2% Lido = 20mg/mL
Max dose Lido plain = 5mg/kg
5mg/kg x 80kg = 400mg max for this pt.
400mg divided by 20mg/kg = 20mL Lido 2%
80
max dose bupivicainee
2.5 mg/kg
175 mg
81
max dose bupivicaine with epi
3 mg/kg
200 mg
82
max dose lidocaine
4.5-5 mg/kg
300 mg
83
max dose lidocaine with epi
7 mg/kg
500 mg
84
Where are esters metabolized
plasma and tissue cholinesterases
85
86
if you have an allergy to one ester..
you have an allergy to them all
87
esters DOA
sshort acting
88
Where are amides metabolized
liver
89
Is there a cross-allergy between amides or between amides and esters
no
90
are more lipophilic and protein-bound
amides
91
resting state of Na channel
channel closed
92
active state
channel open
93
inactive state
channel closed
94
depolarization
cell is less negative (more positive)
Na entering cell
95
channel during RMP
closed
96
channel during depolarization
Open - Na rushes in
97
Inactivation gate
Open- but gate blocks Na from entering
98
inactivation gate opens
cell repolarizes
99
LA molecular structure
aromatic Lipophilic ring + hydrocarbon amine chain + hydrophilic
100
MOA of LA
Produce reversible conduction blockade of impulses along central and peripheral nerve pathways
101
Do locals alter RMP or threshold?
no
102
Rested-closed and inactivated-closed states.
in equillibrium
103
When a local anesthetic interrupts nerve transmission of autonomic nerves but not sensory nerves or motor nerves
differential nerve block
104
Sequence of differential nerve block
loss of autonomic function
superficial pain
touch
temperature
motor function
proprioception
105
Local that spares motor function, but provides analgesia
Bupivacaine
106
what influences sensitivity to LA
diameter
myeiination of nerve fibers
107
Which nerve fibers are numbed first by LA
B
> C fibers
> A gamma/delta
> A beta/alpha
108
high pKA but fast onset due to high concentration of 3%
CHLOROPROCAINE
109
alternate selection when addition of epinephrine to the local anesthetic solution is contraindicated
mepivacaine (lacks vasodilator activity)
110
binding site of bupivacaine
α1-acid glycoprotein
111
serious side effect of bupivacaine toxicity
Cardiac toxicity
most highly protein bound 90% and highly lipid soluble.
112
chosen over Bupivicaine because it is cleared faster to avoid toxicity
ropivacaine
113
has a metabolite
ropivacaine
lidocaine
prilocaine
esters
114
LA that cause methaglobinemia
prilocaine
benzocaine
115
Atypical plasma cholinesterase's account for prolonged effects and toxicity of drugs such as
succinylcholine and chloroprocaine
116
dibucaine number
atypical pseudocholinesterase is facilitated by measurement of the degree of enzyme suppression by dibucaine
117
Anesthesia produced by subarachnoid placement of tetracaine will persist until the drug has been
absorbed into the systemic circulation
118
slow onset LA
procaine (slow and low potency- novacaine)
tetra
bupiv
ropiv
119
fast onset LA's
chloroprocaine
mepivacaine
lidocaine
120
Results from an inadvertent vascular injection or absorption of large amounts of LA from nerve blocks
LAST
121
A toxic level of LA results in decreased
Contractility & arrythmias
Blockade of the cardiac ion channels will affect initiation and propagation of the contraction, and repolarization
122
Progression of subjective symtoms
CNS before CV effects
123
progression of symptoms
1. Excitation, agitation, tinnitus, circumoral numbness
2. Blurred vision, metallic taste, muscle twitching
3. Unconsciousness, seizures, CV and resp. arrest
124
IV injection of bupivicaine causes (3)
hypotension
dysrthymias (PVC, wide QRS, VTAC)
AV block
125
Cardiotoxic plasma concentrations of bupivacaine
8 to 10 µg/mL
126
what drugs worsen bupivicaine cardiotoxicity
Epinephrine and phenylephrine
127
The cardiac toxicity is enhanced by
arterial hypoxemia
acidosis
hypercarbia
128
Treatment of Last
1 Airway (decrease acidosis)
2 seizure (benzo)
3 CV support
4 epi less than 1mck/kg
5 lipid emulsion!!
129
lipid emulsion therapy dose
bolus 20% lipid 1.5ml/kg
0.25-0.6 ml/kg/min 10 min later
max dose 10ml/kg for 20 min
130
EMLA
5% lidocaine–prilocaine
2.5% lidocaine and 2.5% prilocaine
131
IV injection of a local anesthetic solution into an extremity isolated from the rest of the systemic circulation by a tourniquet
BIER block
132
bier block dose
50 mL of a 0.5% solution of lidocaine
133
local
lidocaine
134
meds for peripherals
lido
Bupivacaine, levobupivacaine ropivacaine
135
epidural meds
Lidocaine
Bupivicaine --> levobup, ropiv
136
Addition of DISTILLED WATER lowers the specific gravity of local anesthetic solutions below that of CSF
hypobaric
137
addition of GLUCOSE to LA solutions increases the specific gravity of local anesthetic solutions above that of CSF
hyperbaric
138
max dose of lido in TLA
35-55
139
direct effects of LA on cancer patients
interference with tumor promoting pathways, and direct toxic effects on tumors when used for local infiltration.
140
Indirect effects of LA on Ca patients
result from a reduction of the perioperative stress response and the preservation of the immune response.
141
Plasma concentration is determined by what?
rate of tissue distribution
rate of clearance
142
why is ropivacaine more desirable than bupivacaine in terms of systemic toxicity?
ropivacaine has a faster clearance
143
spinal anesthesia MOA--> what does it work on
preganglionic fibers leaving the spinal cord in anterior ramus
144
TUMESCENT LA max dose
55mg/kg
