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Local Anesthetic Structure Chemistry
chemical structures
279
Pharmacology
02/18/2011

Additional Pharmacology Flashcards

 


 

Cards

Term
What is the only LA that lacks a base N?
Definition
Benzocaine
Term
True/False: LA are tertiary amine bases (proton acceptors)?
Definition
True
Term
How is a tertiary ammonium ion charged?
Definition
in the ionic form
Term
Due to Benzocaine's LACK of a basic N, how does it work?
Definition
entirely by membrane expansion
Term
NH3=?
Definition
ammonia
Term
NH4+=?
Definition
quaternary ammonium ion
Term
C6H6=?
Definition
benzene
Term
Methyl through ethyl =?
Definition
alkyl chains
Term
True/False: esters and amides are intermediate bonds?
Definition
true
Term
Name the three types of AMINES?
Definition
primary, secondary, and tertiary
Term

What are the 5 ester LAs?

 

"Can Big Codes Take Patients"

Definition

1) cocaine

2) benzocaine (americaine)

3) Chloroprocaine (Nesacaine)

4) tetricaine (pontocaine)

5) procaine (novocaine)

 

"Can Big Codes Take Patients"

Term
Are amides AND ester linkages clinically useful?
Definition
YES
Term
What is congener?
Definition
about the same shape
Term
What is another name for an aromatic ring?
Definition
benzene ring (C6H6)
Term
What are the characteristics of a aromamatic (benzene) ring?
Definition
lipophilic, increasing mebrane absorption and penetration of lipid membrane of the nerve
Term
C6H5- = ?
Definition
phenyl radical
Term
What are the subtle changes that can greatly affect potency?
Definition

1) halided to aromatic ring

2) ester-like procaine to procainamide

3) larger alkyl groups on tertiary amide N produce congeners or increased lipophilicty, potency, protein binding , toxicity, and duration

 

Term
At what pH is a tertiary amine protonated (ionic) to create hydrophilic characteristics?
Definition
pH = 7.4
Term
What are weak bases with tertiary amines as proton acceptors?
Definition
LA
Term
At what pH is Lidocaine 65% protonated?
Definition
pH=7.4
Term
What increases AND decreases with the base/ion ratio?
Definition

Increase of pH: surroundings

Decrease pH: surroundings (base trapped in acidic environment)

Example: Fentanyl trapped into acidic tissues of the stomach

Term
How is thipental (acid) reversed?
Definition
with ionization at high alkaline pH
Term
In regard to their physical and biological properties, how does Mepivacaine relate to tetracaine?
Definition
Mepivacaine is of lower potency, hydrophobicity, and pKa
Term
Name the six high potency and greatly hydrophobic LAs and what is there relative conduction-blocking potency?
Definition

Tetracaine, Bupivacaine, Etidocaine, Ropivacaine, Levobupivicaine, and Dibucaine

 

relative conduction-blocking potency = 8

Term
What are the three intermediate potent LAs?
Definition
Mepivacaine, Prilocaine, Chloroprocaine, and Lidocaine
Term

What are the six LA amides?

 

"Locals Do Make Patients Basically Right"

Definition

1) Lidocaine (xylocaine)

2) Dibucaine (Nurpercaine)

3) Mepivacaine (carbocaine)

4) Prilocaine (citanest)

5) Bupivacaine (marcaine)

6) Ropivacaine (naropin)

 

"Locals Do Make Patients Basically Right"

Term
What is the purpose of longer alkyl additions?
Definition

Increased lipophilicity, potency, duration, toxicity and protein binding.

 

Increased potency required fewer ions.

 

Delayed onset = increased latency time

Term
What increases duration?
Definition
increased protein receptor binding and plasma protein binging (reservoir)
Term

Amide or Ester?

 

lidociane to hydrophobic congener etidocaine

Definition
Amide
Term

Amide or Ester?

 

mepivacaine to hydrophobic congeners bupivacaine and ropivacaine

Definition
Amide
Term

Amide or Ester?

 

procaine to hydrophobic congener tetracaine

Definition
Ester
Term
What lacks butyrylcholinesterase?
Definition

spinal fluid

 

 

Term

What is the pKa of most LA?

What dose pKa determine?

Definition

a)8

b) the higher the pKa, the more protonation at a pH of 7.4

Term
Weak bases will protonate at pH of________ forming > 50%______.
Definition

a) 7.2-7.4

b) cations

[B+H = BH; BH = cation (positive ion)]

Term
True/False: Lidocaine is 25% protonated at a pH of 7.4.
Definition
False: Lidocaine is 65% protonate at a pH of 7.4
Term
Membrane concentrations of B/BH are compared to what?
Definition
plasma at 10/1
Term
The membrane pKa of a LA is one unit beow ______ ______ pKa.
Definition
surrounding plasma
Term
In what environment does B concnetrate?
Definition
lipid membrane
Term
What is the purpose of membrane expansion?
Definition

Membrane expansion may contribute to conduction blocking, especially for the nonionic ester benzocaine. 

 

** Benzociane may work exclusively by membrane expansion.**

Term
True/False: Surrounding pH is influential due to an altering % of protonation to base ratio.
Definition
True
Term
What is the cause of trapping bases (LA and opioids) intracellularly?
Definition
the nerve cytoplasm's (axoplasm) acidic environment
Term

What is the pH intracellularly?

It may be different if what enters the cell?

Definition

a)pH= 7.2

b) pH may be differnet is CO2 enters the cell

Term
As intracellular CO2 further lowers the pH what increases?
Definition

protonation (cationic) trapping in the more acidic environment

 

NaHCO3 = NaOH + CO2

Term
Serum protein binding parallels ___(4)____ but is unrelated to _________.
Definition

a) paralells: potency, toxicity, duration and lipophilicity

b) unrelated: receptor proteins mechanism of action

 

Term
True/False: Serum proteins are GOOD models of receptor protein site of action?
Definition
False: serum protein are POOR sites of action
Term
According to sources protein binding is a plasma reservoir associated with _________ and delays both ______ & _________.
Definition
According to sources protein binding is a plasma reservoir associated with duration and delays both onset and clearance.
Term
What is the potency and conduction blocking of chloroprocaine?
Definition
low potency, low toxicity, rapid onset, high dose, high allergy group
Term
At what potency are ropivacaine (Naropin), levobupivacaine (Chirocaine) and dibucaine (Nuperacaine) LAs?
Definition
HIGH potency
Term
True/False: Thecommercial preparations of LAs are BASIC, increasing the water solubility (protination)?
Definition
False: ACIDIFIED
Term
What better preserves epi?
Definition
commercially prepared acidification
Term
What is the purpose of alkalinity?
Definition

1) has no immedicate problem with epi oxidation

2) increases base penetration

3) CO2 from carbonation moves into cell and traps ionic form of local due to acidified cytoplasm

Term
True/False: Preservative should be avoided in the use of spinal LAs.
Definition
TRUE
Term
What are parabins (para hydroxy benzoate)?
Definition
antibacterial but potential allergens and irritate bare nerves
Term
What should you do with discolored solutions and why has the discoloration occured?
Definition
Light oxidized epinephrine, discoloring it.  You should "toss" is (do not use it).
Term
Cm (minimum) is the minimum concentration of LA that will do what?
Definition
block nerve impulse conduction
Term
Cm is a way of comparing ______.
Definition

potency

[analogous to MAC of inhalants]

Term
What provides a 3-D shape to the carbon atom?
Definition
tetrahedral characteristics of its stereochemistry
Term
What is an enantiomer?
Definition
opposite shapes, structures are mirror images, handedness = hand-in-glove
Term
What LAs are examples of congeners (about the same structure)?
Definition
mepivacaine, bupivacaine and ropivacaine
Term
What is a single stereoisomer of racimic bupivacaine (Marcaine, Sensorcaine)?
Definition
levobupivacaine (Chirocaine)
Term
The metabolite structure of benzocaine is very similar to the allergen ______.
Definition
para amino benzoic acid (PABA)
Term
What is a common preservative?
Definition
para hydroxy benzoic acid, methyl paraben
Term
How is the internal receptor on the Na channel for LA mainly acessed?
Definition
from the cytoplasm
Term
increased potency = ?
Definition
less drug, more lipid soluble and more protein binding
Term
What is the approximate pKa of LA?
Definition
8
Term
LA bind to Na channel receptors best when the channels are in a (open/inacitve) OR (closed/active) state.
Definition
LA bind to Na channel receptors best when the channels are in the open/inactive state.
Term
Procainamide is ____ excreted and very little ______.  Some_____ _____ takes place.
Definition

Procainamide is renal excreted and very little hydrolysis.

 

Some liver conjugation.

Term
LA work on ______ gated sodium channels and muscle relaxants work on _____ gated sodium channels
Definition

LA: voltage gated Na channels

MR: ligand gated Na channels

Term
LA and muscle relaxants both prevent membranes from reaching _________.
Definition
transmembrane threshold potential
Term
What is the Epinephrine concentration and test dose for LA use?
Definition
Epinephrine 1:200,000=5mcg/cc
Test Dose 3cc=15mcg
Term
What is the max dose for Epinephrine for LA use?
Definition
200-250 mcg
Term
True/False: Fresh Epi is best for use in LA?
Definition
True
Term
What is the pH of a fresh Epi vial?
Definition
pH around 3-4
Term
What is a "caution" when using Epi with a beta blocked or eldery patient?
Definition
Pulse may not increase
Term
What is the regional, Lidocaine dose for an upper extremity?
Definition
3mg/kg Lidocaine
Term
What is the concentration for regional Lidocaine?
Definition
2%= 2gm/100cc
2% = 20mg/cc
Term
What is the dose and concentration of regional Lidocaine for an ARM?
Definition
250mg with NS to 50cc
5mg/cc = 0.5%
Term
What is the concentration and dose of regional Lidocaine for a LEG?
Definition
250mg to 100 ml = 0.25%
2.5mg/cc = 0.25%
(extra volume for leg aids spread)
Term
At what landmark on a leg would be a concern for tourniquet placement?
Definition
Tourniquet on a superficial peroneal nerve (lateral tibial) is a concern.
Term
What LA is of concern for cardiovascular collapse (stone heart)?
Definition
Bupivacaine
Term
List LA plasma levels in order of highest to lowest for anatomic injection site.
Definition
Highest with intercostal, caudal, epidural, brachial plexus and lest with SQ.
Term
At what concentration would Epi be 2mcg/ml?
Definition
Epi 1: 500,000 = 2mcg/ml
Term
Epi 1:1 = ____.
Definition
Epi 1:1= 1gm/1cc OR 1kg/1L
Term
Epi 1:1,000=______.
Definition
Epi 1:1,000= 1mg/ccc
Term
0.2mg Epi 1:1,000 = _____.
Definition
0.2 cc Epi 1:1,000 = 200mcg
Term
If you use 7mg/kg Lidocaine, what is the max dose of a solution containing Epi?
Definition
500mg
Term
All LA are ____ _____ bases (proton acceptors).
Definition
tertiary amines
Term
What is the charged ionic form of a tertiary amine base?
Definition
tertiary ammonium ion
Term
What do schwann cells surround all nerves to produce what?
Definition
myeline covering large nerves
Term
Where is schwann cell produced myeline found?
Definition
on large A and B nerve fibers
Term
Where is schwann cell produced myeline found?
Definition
on large A and B nerve fibers
Term
Where is schwann cell produced myeline found?
Definition
on large A and B nerve fibers
Term
What is saltory?
Definition
nodes of ranvier increased rate of conduction
Term
What type of Schwann cell sheath is on C fibers and nerves at the NMJ?
Definition
axolemma
Term
Describe the antaomy of a nerve.
Definition
A nerve is made up of fascicles which are groups or bundles of nerve axons
Term
Describe epineurium, perineurium and endoneurium.
Definition
Epineurium convers a nerve
Perineurium covers a fascicle
Endoneurium covers a nerve axon.
Term
Describe the electrolyte composition of a cell's interior cytoplasm.
Definition
cell interior cytoplasm is righ in K and poor in Na and Cl. this is reverse of sea water and plasma
Term
What is axolemma?
Definition
structure of ansonal membrane: biologic molecular lipid bilayer of amphiphilic (lipo and hydro) phospholipids
Term
What is a "fluid mosaic"?
Definition
zwitterions contain positive and negative
Term
Where is the site of action for LA?
Definition
Na channels concentrated at nodes of Ranvier
Term
What is refractory?
Definition
explains unidirectional propagation
Term
Describe A alpha nerves.
Definition
myelinated, large, fast, motor function
Term
Describe A beta nerves.
Definition
myelinated, large, fast, tactile and proprioception function
Term
Describe A gamma nerves.
Definition
myelinated, intermediate diameter, intermediate speed, muscle tone function, highly susceptible to LA block
Term
Describe A delta nerves.
Definition
nyelinated, small diameter, slow; pain, cold temperature and touch function; more likely to be blocked by LA
Term
K ICF: ECF ratio?
Definition
30 ICF: 1 ICF
Term
There are three Na channel states. What are they?
Definition
Closed/Resting
Open/activated
inactivated/transition
Term
Describe the difference between the outer and inner gates.
Definition
Outer: voltage dependent
Inner: time dependent
Term
True/False: K channels precede Na channels in both opening and closing?
Definition
FALSE: Na channels precede K channels in both opening and closing
Term
What happens when a channel is resting (closed)?
Definition
activation gate (voltage) is closed and inactivation gate (time) is open. thus, no ion flow.
Term
What happens with activation of a gate?
Definition
activation (charge) abruptly allows Na influx by opening outer gate until inactivation gate (time) slowly closes for a while.
Term
What does it mean for a gate to be inactivated?
Definition
a transition phase between activated (open) and resting (closed) Na channels
Term
True/False: Being refractory to a membrane's voltage changes = unresponsive?
Definition
TRUE
Term
When a membrane is unresponsive what happens to the inner time-dependent gate?
Definition
it is closed
Term
What is explained by positive feedback on resting adjacent voltage gates?
Definition
propagation and inactivation due to time gate
Term
True/False: Time gate explains unidirectional?
Definition
TRUE
Term
True/False: LA both prolong inactivated states and bind to open or about to open channels more than LA bind to resting state?
Definition
TRUE
Term
What are three descriptors of LAs?
Definition
use-dependent
frequency-dependent
phasic block
Term
How do LA bind to voltage gate receptors?
Definition
from inside cytoplasm or the membrane
Term
True/False: Once any of the three states of receptors are bound by a LA, it is active?
Definition
FALSE: it is inactive
Term
What do LA not do to the channel from plasma or cytoplasm?
Definition
they do not "plug" the channel
Term
What plugs external opening and is a toxin?
Definition
tetrodotoxin
Term
Why can Na only fit through Na channels?
Definition
Na holds 5 waters and is too big for the smaller K channel. K is too big for waterless Na ions. na is stripped of water when passing through Na channels. SO...Na and K rates are ion specific.
Term
Describe the characteristics of MODERATELY hydrophobic LA solutions.
Definition
act fastest due to lower potency, so they are able to be delivered in higher concentrations
Term
Describe the characteristics of HIGHLY lipophilic LA solutions.
Definition
very potent but low concentration, so they have a slow onset
Term
At what pH are LA botted as hydrochloride salts and how does the environment contribute to the LA?
Definition
LA are bottled as hydrochloride salts at a pH of 6.0, thus they are ionic and more water soluble.
Term
What does a base add to LA and epinephrine (1:200,000)?
Definition
stability
Term
What is a function of pH and pKa?
Definition
ionization
Term
Why if Fentanyl trapped in the stomach?
Definition
low pH favors ions for bases
Term
True/False: potent drugs are used at low concentrations, thus clow onset (long latency) even with high lipophilicity?
Definition
TRUE
Term
True/False: Hydrophilicity parallels potency, toxicity, protein binding, and duration?
Definition
FALSE: lipophilicity
Term
What favors onset: acidity or alkalization?
Definition
alkalization
Term
What hinders onset, but favors trapping?
Definition
acidity
Term
What enters the cell, lowering the intracellular pH?
Definition
CO2
Term
What increases plasma pH for better membrane potential?
Definition
bicarbonate
Term
An increase or decrease in plasma pH favors what?
Definition
rapid onset and long duration of LA
Term
When can bases be trapped in an acidic environment?
Definition
nerve axoplasma, fetus, brain and stomach
Term
TRUE/FALSE: LA Do change resting membrane potentials and/or thresholds?
Definition
FALSE: LA DO NOT change the potentials or thresholds
Term
How do LA affect NA channels?
Definition
LA slow and decrease the degree of depolarization at Na channels and eventually the membrane cannot reach threshold.
Term
What is the effect of repolarization?
Definition
repolarization overshoots threshold so the potential is further below resting potential (partially refractory).
Term
How do electrolyte imbalances influence a membrane potential?
Definition
Lyte imbalances influence the resting membrane potential threshold and action potential. low Na lowers action potential, low Ca and high Mg lowers threshold, low K lowers resting membrane.
Term
When channels do not open due to LA, what happens to Na, K, and Ca currents?
Definition
they are reduced
Term
What effect do toxins have on chnnels?
Definition
they may externally occlude or destroy channels
Term
How does membrane expansion effect a membrane?
Definition
it may play a minor role based on lipophilicity
Term
True/False: LA block open (active) more than transition (inactive) and much more than closed (resting)?
Definition
TRUE
Term
True/False: LA bind inactive sites quicker and longer?
Definition
FALSE: ACTIVE sites
Term
What three factors enhance block on repetitively stimulated nerves?
Definition
frequency-dependent
use-dependent
phasic inhibition
Term
With a differential block is sensory or motor blocked first?
Definition
sensory
Term
What two LA have equal or greater motor to sensory?
Definition
marcaine 0.75% or etidocaine (surgery)
Term
Which two LA are more sensory than motor?
Definition
ropivacaine and bupivacaine 0.25% or 0.5% (OB)
Term
True/False: Chronic pain is hard to block with low doses?
Definition
FALSE: low doses (bupivicaine in the pain clinic)
Term
Frue/False: It is certain that bupivicaine stone heart is due to prolonged concentration in active cardiac muscle or nerve.
Definition
FALSE: we are not sure
Term
_________ gets the drug to the receptor and ________ (charge) keeps it there.
Definition
hydrophobicility = receptor
hydrophilicity= keeps it there
Term
Dissociation of LA from receptors depends on 4 factors affecting the charge that keeps it there. What are the four factors?
Definition
structure
pKa
pH
hydrophobicity
Term
What is in parallel to duration?
Definition
lipophilicity
protein receptor affinity
potency
Term
What two lytes stabilize the outer cell membrane?
Definition
Ca and Mg
Term
If Ca stabilized the excitatory threshold what dose low Ca do?
Definition
low Ca narrows resting membrane potential to threshold (like spontaneous firing following a parathyroidectomy)
Term
What raises the seizure threshould?
Definition
increased Mg (OB an pheocromocytoma)
Term
True/False: Ca interferes with Mg on muscle contration, lowing vascular and uterine tone.
Definition
FALSE: Mg interferes with Ca
Term
What effect does Mg have on NMJ?
Definition
Mg decreases ACh presynaptic release at NMJ while Ca increases this ACh release.
Term
What lyte determines the resting membrane potential?
Definition
K
Term
What channels are voltage-dependent?
Definition
double gated Na channels
Term
What channels are always voltage independent?
Definition
ligand gated channels (GABA and ACh)
Term
______ of _______ is rapid as exposure to "the" plasma cholinesterase.
Definition
Metabolism of esters
Term
True/False: Chloroprocaine in OR is slow and tetracaine in spinals is short?
Definition
FALSE: chloroprocaine = short
tetracaine = slowW2~S2
Term
Because CSF has not butyrylcholineresterase, the rational in the use of __________ (novocaine) for intermediate spinal duration.
Definition
procaine
Term
Esters may yeild this potential allergen.
Definition
PABA: para-amino benzoic acid
Term
What ester undergoes significant metabolization in the liver as well as ester hydrolysis?
Definition
cocaine
Term
True/False: amides are metabolized in teh liver and are less stable in solution?
Definition
FALSE: more stable
Term
Potency is primarly from lipophilicy or hydrophilicity?
Definition
lipophilicity
Term
High potency = _______ dose.
Definition
low dose (low # of molecules
Term
What effect does Epinephrine have on a block?
Definition
Epinephrine increase the desity of the block (increases potency) by reducing wash-out by blood flow due to vasodilation, as significant effect by many LA. Epi keeps LA at site longer, increasing duration.
Term
Onset = ______.
Definition
latency
Term
What determines latency?
Definition
dose and concentration
Term
TRUE/FALSE: potent drugs are of high concentration, rapid onset/short latency?
Definition
FALSE: low concentration, slow onset, prolonged latency
Term
What determines toxicity?
Definition
systemic dose
Term
________ affect on B/B+ shortens onset.
Definition
Alkalinization
Term
True/False: protein binding effects duration?
Definition
true
Term
Plasma proteins are reservoirs for LA and thus decrease availability of LA for what 3 things?
Definition
1)block
2) metabolism
3) removal from site of action
Term
________ are proteins with druation affected by binding.
Definition
receptors
Term
LA have initial vaso- (constriction/dilation) followed by (constriction/dilation)?
Definition
LA have initial vasoconstriction followed by dilation. this is a biphasic property.
Term
what two LA are vasoconstrictors.
Definition
cocaine and maybe ropivacaine (stereospecific)
Term
What affect does Epi have on the constriction of LA?
Definition
maintains the initial vasoconstriction, slowing redistribution and prolonging duration
Term
What LAs are mostly association with dose dependent differential block?
Definition
Bupivicaine and ropivacaine, since epidural in OB preserves abdominal muscles for pushing
Term
Low or high concentrations of LA seem to produce differential blocks better?
Definition
low concentrations, like bupivacaine
Term
True/False: the theory of differential blocks is poorly understood.
Definition
true
Term
_____, ______, and _______ effect onset, effectiveness, spread and duration of LAs.
Definition
dosage, concentration, volume
Term
How many nodes on myelinated nere fibers must LA block and what fibers are they
Definition
LA need to block 3 or more nodes of the large A and/or B fibers
Term
What may increase bupivacaine's toxicity?
Definition
Epinephrine
Term
While decreasing blood flow, washout is probably also influenced by what three things?
Definition
1) fat storage
2) receptor binding
3) plasma protein binding
Term
Site of injection: ______ has the slowest onset and longest duration with motor and proximal blocks before sensory and distal blocks due to exposure.
Definition
Brachial plexus (lots of membranes to penetrate and low vascularity)
Term
A brachial plexus block has proximal and motor toward mantal so _____ and _____ is slowest in onset.
Definition
so core distal and sensory is slowest in onset
Term
Spinals (no myeling and low dose) have ____ onset and ____ duration.
Definition
rapid onset and short duration
Term
these fibers are blocked before/above sensory A-delta nd C fibers.
Definition
autonomic B fibers
Term
A-delta and C fibers are blocked before/above these fibers at two-segment regression.
Definition
motor A-fibers
Term
This is blocked before CNS vagus.
Definition
peripheral SNS blocked before CNS vagus
Term
What enhances penetration?
Definition
carbonation (increases B)
Term
What causes ionization?
Definition
CO2 diffusion into axoplasma (decreased pH)
Term
Where are ions trapped?
Definition
axoplasma
Term
Alkalization is best for both of these two characteristics.
Definition
fast onset and long duration
Term
Mixtures can combine rapid onset LA with ____ _____ LA.
Definition
long duration
Term
True/False: LA do not potentiate or nullify each other?
Definition
TRUE
Term
What three LA are combined for spinal?
Definition
procaine (novocaine) + tetracaine (pontocaine) or lidocaine + dupivacaine
Term
what two LA are combined for OB?
Definition
chloroprocaine (nesacaine) + bupivacaine
Term
What LA produce a relatively long spinal block due to low plasma cholinesterases in CSF?
Definition
prociane (novocaine) and other esters
Term
What medical condition can change protein binding?
Definition
pregnancy (hormones)
Term
True/False: low protein binding decrease placental transfer?
Definition
FALSE: high protein binding
Term
True/False: Esters are metabolized before they can reach the fetus?
Definition
TRUE
Term
What physiological change effects a block in pregnancy?
Definition
smaller spinal/epidural space
Term
What LA is highly ionic, slwoing the spread to a fetus?
Definition
Choroprocaine
Term
Tetracaine is highly water soluble at low pH of___.
Definition
pH 7.4 (high pKa 8.4)
Term
Why is tetracaine not used in brachial plexus blocks, but is okay for spinals (exposed nerves)?
Definition
only 14% is nonionic at pH 7.4 so giving it poor penetration
Term
What is the pH of topical EMLA cream (lidocaine/prilocaine)?
Definition
high basic pH
Term
How many minutes does it take for EMLA cream to be equal to IV effect and for a deep effect?
Definition
30 minutes for IV and 2 hours for deep effect
Term
What is the greatest risk for newborns and infants when using EMLA cream?
Definition
prilociane toxicity (methemoglobin: metabolite replaces oxygen on Hgb)
Term
what topical anesthetic is used for intubation, oral, burns, or hemorrhoids that may produce stystemic toxicity?
Definition
topical benzocaine (ceticaine) or lidocaine
Term
What two LAs can be used in all regional blocks, making them popular?
Definition
bupivacaine and lidocaine
Term
What LA is especially prolonged by Epi?
Definition
Lidocaine
Term
True/False: injection pain of LA is due to the low pH of epinephrine?
Definition
true
Term
What are the doseages in mg for potent, intermediate, and low potency LA?
Definition
potent: 200mg
intermediate: 500mg
low: 1000mg
Term
By adding epi to LAs you can use how much more drug without systemic effects and increase duration by 50%.
Definition
20% more drug
Term
What drug (without epi) have a maximum of 150-200 mg?
Definition
cocaine
Term
Peripheral nerve blocks are minor, so how many nerves do they block?
Definition
a single nerve
Term
How do you select a LA for a PNB?
Definition
all locals have fast onset so select LA for its duration
Term
Can you use Epi in PNB to prolong the sensory and motor of the block?
Definition
YES
Term
What kind of post-sugical pain can by controlled well by intrapleural, intercostal, or epidural blocks due to their high systemic uptake?
Definition
abdominal/thoracic post-surgical pain
Term
What is the most common major PNB?
Definition
brachial plexus
Term
TRUE/FALSE: PNB are used for long lasting anesthesia?
Definition
FALSE: pain relief
Term
In what order dose a PNB set in?
Definition
motor > sensory > SNS depending on the axon location in mantle more than serve size or myelination
Term
In what order do central blocks set in?
Definition
SNS> sensory > motor
Term
Central Neural Blockade order of block and location of dermatone.
Definition
SNS 2 dermatones above sensory which is 2 dermatones above motor
Term
What are the characteristics of intermediate LA, Lidociane and procaine when used for a CNB with Epi?
Definition
Lidocaine and Procaine last 1-2 hours with Epi prolonging its duration by 50%
Term
How long do long-lasting LA work when used with Epi?
Definition
3-5 hours
Term
The motor block of bupivacaine depends on the percentage used. What percentages can be used?
Definition
0.25, 0.50, or 0.75 %
Term
The concentration of a LA affects what?
Definition
dose, volume, differential block and spread
Term
How do you mix tetracaine for a CNB and how long is its duration ?
Definition
spinal tetracaine 1cc 1%(10mg) diluted to 0.5% mixed with 1cc 10% glucose = 2 cc total for a 3-4 hour hyperberic spinal.
Term
how is lidocaine mixed for a CNB and how long does it last?
Definition
100 mg Lido (2cc 5%) premixed with glucose 7.5% gives a 45-60 minute block
Term
What LA can be mixed well with tetracaine 1% (10mg) to speed its slow onset.
Definition
prociane 1cc 10% (100mg) + tetracaine 1cc 1% (10mg)
Term
Because tetracaine exhibits poor membrane crossing and low CSF butyrylcholinesterase it is chosen for what blocks?
Definition
it is good for spinals but poor for epidural and brachial plexus blocks
Term
True/False: tetracaine resembles intrathecal MS since both are highly nonionic?
Definition
FALSE: highly ionic
Term
What type of LAs do hypobaric spinal require?
Definition
preservative free water for 4-5 cc total volume
Term
What pharmacokinetic characteristic is affected by patient status?
Definition
biotransformation and excretion
Term
What age group have prolonged duration of LA in plasma which probably reflects decreased liver metabolism of amides?
Definition
extreme ages
(lower butyrylcholinesterase in older males)
Term
Describe the signs of Lidocaine toxicity in order of occurance.
Definition
1) lightheadedness, tinnitus, circumoral and tongue numbness
2) visual disturbances
3) musclular twitching
4) convulsions
5) unconciousness
6) coma
7) respiratiory arrest
8) CVS depression
9) CVS collapse
Term
What changes make a patient more sensitive to seizures?
Definition
elevated CO2 and acidosis lowers the seizure threshold and increases LA trapping in brain cells
Term
What affect dose acidosis play on the body?
Definition
acidosis increases CBF and decrease protein binging for more free drug availability to the CNS
Term
True/False: cardiac fast Na channel block will slow depolarization?
Definition
true
Term
What channel block may decrease contractility?
Definition
slow Ca channel blockade
Term
True/False: Toxicity parallels potency?
Definition
true
Term
What drug is very arrhythmic?
Definition
Bupivacaine (goes in fast if a high concentration is used and has prolonged duration)
Term
What is the max concentration of bupivicaine that is allowable in OB patients?
Definition
0.5%
Term
What condition may be precipitated by bupivacaine?
Definition
stone heart
Term
What are two better LA choices over Bupivacaine?
Definition
levobupivacaine (chirocaine) or ropivacaine (naropin)
Term
What possible factors makes Ropivacaine a better coice than bupivacaine in OB?
Definition
1) vasoconstriction
2) slighlty shorter duration
3) more differential
4) have less placenta transfer
5) less cardiac toxicity
Term
What three things potentiate negative inotropic and chronotropic action and increase arrhythmias, enhancing toxicity of bupivacaine?
Definition
hypercarbia, hypoxia, and acidosis
Term
What LA can cause methemoglobinemia and how can this be minimized?
Definition
using Prilocaine (Citanest) at a max dose of 500 mg
Term
Oxygen and prilocaine metabolite are _____ agents.
Definition
oxidizing agents (bind heoglobin)
Term
what can be administered to reverse methemoglobinemia?
Definition
reducing agent methylene blue 100 mg
Term
PABA is an allergen. what other LA have structure similarities?
Definition
procaine (novocaine) and benzocaine metabolite and methylparabin (Na methyl para-hydroxybenzoate: salt preservative)
Term
True/False: allergies due to LA amides are most common?
Definition
FALSE: rare
Term
What two things make LA cytotoxic in spinal, epidural or in TIVA?
Definition
preservatives and high doses
Term
What is cauda equina syndrome?
Definition
dense concentration of LA on non-myelinated nerves
Term
What LA has most recently been a suspect of spinal toxicity, even besides micro catheters?
Definition
Lidocaine
Term
What is the current name for transient radicular neuropathy (TRN)?
Definition
Transient Radicular Irritation (TRI) or Transient Radicular neurologic symptoms (TNS)
Term
What are some reasons for symptoms (radicular [butt] pain, back pain, hypothesia, parasthesia) resembling TRI?
Definition
epi use, position (lithotomy), aging, stretching
Term
When is TRIs onset and how long does it last?
Definition
TRI usually onsets in 24 hours and is transient for a few days up to months. Direct muscle injection with LA causes only transient changes.
Term
What was really the cause of chloroprocaine (nesacaine) permanent toxicity?
Definition
Na bisulfate additive at low pH
Term
rapid metabolis, onset, and short duration makes what LA safe for labor epidural and the fetus?
Definition
chloroprocaine (now available as preservative free or with another non-toxic preservative)
Term
What is the teatment for seizures?
Definition
1) oxygen
2) seizure control (pentothal, propofol, midazolam)
3) airway control
Term
When raising the seizure threshold with Benzos what may you be missing?
Definition
early warning CNS signs before cardiovascular collapse, such as with lidocaine IV regional blocks
Term
What drugs may be used to treat seizures that have a fast onset, short duration and are easy to titrate?
Definition
barbs (anticonvulsants), propofol, midazolam, and Succs (20-40mg): have them ready with a plan!
Term
What blocks catacholamine reuptake and accounts for its unique vasoconstrictive effects and probably its other stimulatory effects.
Definition
Cocaine (blocks reuptake of norepi and dopamine [pleasure transmitter])
Term
Dibucaine amide inactivates __% of normal and __% atypical plasma cholinesterase
Definition
80% normal
20% atypical
Term
The % of plasma cholinesterase that Dibucaine inactivates indicates what?
Definition
butyrylcholinesterace quality, but not quantity
Term
One atypical gene = __% & Two atypical genes = __% inhibition of dibucaine (1/3200 patients).
Definition
One atypical gene = 50-60%
Two atypical genes = 20-30%
Term
List in order of concentration for equivalent depth of block the 8 most commonly used LA. (N fig 9-10)
Definition
Procaine & Chloroprocaine
Mepivacaine & Prilociane
Lidocaine
Tetracaine
Bupivacaine
Etidocaine
Term
What is the max dose (with epi) for Chloroprocaine, Lidocaine, and Bupivicaine ?
Definition
chloroprocaine: 1000mg
lidocaine: 500 mg (7mg/kg)
bupivacaine: 225 mg (175 mg plain)
Term
From what nerve fibers does pain originate?
Definition
myelinated A delta and unmyelinated C fibers
Term
What block site is known for having the highest plasma concentration and what site follows behind it
Definition
intercostal then caudal, epidural, brachial plexus