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My Advanced anesthesia 2 > Quiz 5 (Local Anesthetics) > Flashcards

Quiz 5 (Local Anesthetics) Flashcards

1
Q

1st Local Anesthetic
1st Synthetic Local (Ester)
1st Amide Local

A

1st Local Anesthetic Cocaine 1884
1st Synthetic Local (Ester) Procaine 1905
1st Amide Local Lidocaine 1943

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2
Q

Chemical Structure of both amide and Ester

A

-Lipophilic and hydrophilic portion separated by hydrocarbon
-Lipophilic portion is the Benzene ring
Necessary for activity

Ester
-CO-
Amide
-NHC-

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3
Q

extracellular vs intracellular pH

A

Extra - 7.4

Intra - 7.0

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4
Q

Enantiomers
s
r

A

Left = sinister

Right = rectus

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5
Q

S enantiomers - What’s the benefit? 2 examples?

A

Found to be less neuro- and cardio-toxic

Ropivacaine and Levobupivacaine

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6
Q

MOA of local anesthetics (main site of action)

A

Inhibit Na+ ions passage through ion-selective Na+ channels:

  • Slows rate of depolarization
  • Threshold potential not reached
  • No action potential propagated
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7
Q

L.A.’s Binds to receptors in ____________________ states

A

inactivated/activated

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8
Q

Nerves with more activity = ______ blockade

A

faster

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9
Q

look at slide 12

A

.

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10
Q

other sites of action for L.A.’s

A

-Voltage-dependent potassium ion channels
(Much lower affinity)

  • Calcium ion currents (L-type)
  • G protein-coupled receptors
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11
Q

Cm for motor about _____ sensory

A

twice

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12
Q

factors that increase and decrease Cm

A

Increases:
-Larger diameter

Decreases:

  • Higher frequency
  • Higher pH
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13
Q

Epidural vs Spinal Cm and dose

A
  • Unchanged Cm

- Direct access to nerves = less amount

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14
Q

Nodes of Ranvier, Must block?

A

at least 2, preferably 3

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15
Q

order of blockade of fibers

A 
B fibers
C and A-delta fibers
A-Gamma fibers
A-Beta fibers
A-Alpha fibers
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16
Q

which fibers travel faster?

A

Myelenated

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17
Q

ATP-TP-MVP acronym

A
  • Autonomic
  • Temperature
  • Pain
  • Touch
  • Pressure
  • Motor
  • Vibration
  • Proprioception
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18
Q

What form to cross lipid bylayer?

A

Un-ionized

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19
Q

Locals with pks nearest physiologic pH?

A

Faster onset

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20
Q

all are typically weak bases, which on is a weak acid and what pH?

A

Benzocaine

  • pKa – 3.5
  • Does not ionize based on pH
  • Also does not block by same mechanism
  • Mechanism is unknown
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21
Q

adding bicarb does what?

A

makes pH closer to physiologic pH, making onset quicker by 3-5 mins

also lessens sting of local infiltration

22
Q

Absorption into systemic circulation

Influenced by:

A
  • Site of injection
  • Dosage
  • Use of Epi
  • Characteristics of drug
23
Q

Distribution :

A 
1st large uptake to lungs
2nd distribution to high perfused tissue 
(heart, brain, kidneys)
3rd distribution to low perfused tissue
(muscle and fat)
Amides are more widely distributed
24
Q

Why is placental transfer important?

A

Ion trapping

25
Q

Why do we worry about which vasopressor can cause fetal acidosis?

A
  • Once un-ionized local crosses placenta and hits low fetal pH more drug is ionized and can’t cross back
  • Build up of trapped local in fetal circulation leads to toxicity in fetus
26
Q

Lipid Solubility

A

More lipid soluble means easier to cross lipid by-layer

27
Q

Onset related to :

A
  • State of Ionization – most important

- Lipid Solubility

28
Q

Duration of Action related to:

A
  • Protein Binding
  • Lipid Solubility

(Higher affinity to proteins and lipids = stronger attachment. Drug remains close to the Na+ channels to act longer)

29
Q

Amides metabolism

A

Mainly hepatic metabolism

30
Q

Amides fastest to slowest

A

Fastest:
-Prilocaine 30 sec – 1 min

Intermediate:

  • Lidocaine
  • Mepivicaine

Slow:

  • Etidocaine
  • Bupivacaine
  • Ropivacaine
31
Q

Esters metabolism

A
  • Rapid hydrolysis
  • Cholinesterases
  • Mostly plasma, lesser liver
32
Q

Esters fastest to slowest

A

Rapid:
-Chloroprocaine

Intermediate:
-Procaine

Slow:
-Tetracaine

33
Q

One exception to hydrolysis?

A

Cocaine – significant metabolism in liver

34
Q

which L.A. group has allergy concerns? what is it?

A

Esters

PABA

35
Q

What common local injection site contains little to no cholinesterase enzyme?

A

CSF

Must wait until drug goes into systemic circulation for hydrolysis

36
Q

Plasma Cholinesterase Inhibited in:

A
  • Chemotherapy patients
  • Liver disease
  • Increased BUN
  • Parturients
  • Deficiency
37
Q

Epi dosing

A

1:200,000 or

5 mcg/ml

38
Q

Epi helps LA by:

A
  • Limits systemic absorption
  • Maintains drug concentration around nerves
  • Can prolong Lidocaine by 1/3
  • No effect to onset
  • Helps to decrease toxicity
39
Q

Which 2 local anesthetics have no vasodilator activity?

A
  • Cocaine

- Ropivacaine (only parenteral with vasoconstrictive activity)

40
Q

Clonidine as an LA additive

A
  • Preservative free alpha-2 agonist
  • Enhances neuraxial anesthesia
  • Can be used in combo with Opioids (additive)
41
Q

effects of mixing LAs?

A

additive (not synergistic)

42
Q

how much drug in 40 mL 1%? 80 mL 0.5%?

A

40mL of 1% or 80mL of 0.5%

Both 400 mg

43
Q

Tx of seizures

A

100% o2

Benzos

44
Q

memorize slide 44

A

.

45
Q

Systemic levels related to blood flow of tissue

Fastest to Slowest

A
  • IV
  • Tracheal
  • Intercostal
  • Caudal
  • Paracervical
  • Epidural
  • Brachial Plexus
  • Subarachnoid
  • Subcutaneous

In Time I Can Please Everyone But Suzi and Sally

46
Q

indications of spinals issues in caudal block

A
  • Sacral Dimple

- Hairy Nevi

47
Q

Cauda Equina Syndrome

A

Diffuse injury across lumbosacral plexus

  • Various degrees of sensory anesthesia
  • Bowel and bladder sphincter dysfunction
  • Paraplegia
48
Q

Anterior Spinal Artery Syndrome

A

Lower extremity paresis and variable sensory deficit

49
Q

look at slide 47

A

.

50
Q

Lipid Emulsion (20%) Therapy

A
  • 1.5 mL/kg (lean body mass) IV over 1 minute
  • 0.25 mL/kg/min
  • Repeat Bolus once or twice for persistant cardiovascular collapse
  • Double infusion rate to 0.5 mL/kg/min if BP remains low
  • Continue infusion for at least 10 min after circulatory stability
  • Upper limit: Approximately 10 mL/kg lipid emulsion over first 30 minutes
51
Q

treatment for methemeglobinemia?

A

methylene blue

52
Q

look at slide 51

A

.

My Advanced anesthesia 2 (12 decks)

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