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004 - Neuropharmacology > 02 - Local Anesthetics > Flashcards

02 - Local Anesthetics Flashcards

1
Q

(Mechanism of Action)

  1. What is the main site of action? no effect on what?
  2. reversible block of what?
  3. direct interaction with what channels?
  4. Decrease or prevention of permeability of membrane to what ions?
  5. increase or decrease the concentration? increase or decrease the rate and degree of depolarization?
A
  1. excitable cell membrane (no effect on RBC)
  2. impulse conduction
  3. voltage sensitive Na channels
  4. Na+ ions only
  5. increase; decrease
    (remeber: depolarization is caused largely by the influx of sodium into the cell)
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2
Q

1-2. The resting membrane potential is mainted by what two things?

A
  1. impermeability of the membrane to sodium
  2. sodium pump which extrudes sodium

(RESTING MEMBRANE POTENTIAL IS NOT AFFECTED - possible test questino)

(the more sodium channels there are to act on… the more potent the LA are)

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3
Q

(Differential effects on nerve fibers)

  1. do local anesthics depress small, unmyelinated fibers… or larger, myelinated fibers more readily
  2. Which are more sensitive… sensory fibers or motor fibers?
  3. What is the first modality to disappear?
A
  1. small, unmyelinated (opposite of pressure block)
  2. sensory
  3. pain (then cold, warmth, touch, and deep pressure - this can vary though)
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4
Q

(Types of Local Anesthesia)

(topical (surface) anesthesia)

  1. applied to what?
  2. alone or in conjuction with other drugs (proparacaine, lidocaine, benzocaine)

(local infiltration)

  1. directly into what?
  2. what is an advantage?
  3. disadvantage?
A
  1. epithelial surface
  2. tissue (relatively large volumes of dilute anestetic intradermally or into deeper tissues
  3. good anesthesia without disruption of normal function
  4. small area anseshetized
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5
Q

(Types of Local Anesthesia)

(Regional (perineural) anesthesia)

  1. what two blocks?
  2. injection of large volumes of local anesthetic to do what?

(Nerve block or conjuction block)

  1. inject into or around what?
  2. what is an application in horses?

(Paravertebral block)

  1. block what?
  2. used in what?
A
  1. line block or field block
  2. block a surgical field
  3. individual nerves or nerve plexuses
  4. lameness diagnosis
  5. successive dorsal and bentral branches of emergent spinal nerves close to vertebral column
  6. standing surgery in ruminants
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6
Q

(Types of Local Anesthesia)

(epidural anesthesia)

  1. inject through what into what?
  2. used in what?

(Intravenous anesthesia: decreased NMJ activity too)

  1. inject IV where?
  2. application - amputation of claw in cow
A
  1. through intervertebral space into epidural space
  2. obstetrics (woman’s reproductive health) (bupivacaine)
  3. extremely distal to an occluding tourniquet
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7
Q

(Types of LA)

(Intrathecal of spinal anesthesia)

  1. directly into CSF within what?
  2. rarely used in vet med… why?
A
  1. subarachnoid space
  2. due to risk of spinal cord damage and diffusion centrally
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8
Q

(Toxicity and Other Sites of Action)

  1. Usually from what?

2-3. dependent on what two things?

A
  1. inadvertent iv injection (also from too large of volume/strenght)
  2. rate of absorption of drug systematically
  3. rate of destruction (ie metabolism)
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9
Q
  1. LA also affect transmission at neuromuscular junctions, thus have effects on what muscles?

Similar effects are seen where?

A
  1. cardiac, smooth, skeletal (altering AP in these tissues)

at autonomic ganglia

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10
Q
  1. In general which is more susceptibe to systemic action of local anesthietics? CNS or cardiovascular?
  2. What is a major sign of toxicity?

what happens?

  1. Increasing the dose ultimately results in inhibition of both inhibitory and excitatory pathways leading to what?
A
  1. CNS
  2. CNS excitement (muscle tremors/convulsions)

blockade of inhibitory pathways in cerebral cortex

  1. a generalized state of CNS depression
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11
Q

(Cardiovascular)

  1. what is primary site of action?
  2. how is vascular smooth muscle affected by LA
  3. what are used as antiarrhythmic agents in heart?
  4. toxicity can be from direct action on the myocardium causing decreases in what? What markedly potentiate cardiodepressant effects?
  5. What can cause cardiovascular collapse?
A
  1. myocardium
  2. relaxes (exception… cocaine)
  3. lidocaine and procainamide
  4. eletrical exciation, conduction rate, and force of contraction; acidosis and hypoxia
  5. overdose
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12
Q

know this

A
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13
Q

(CNS)

  1. do therapeutic doses produce central effects?
  2. high doses can cause drowsiness, visual and auditory disturbances, and restlessness
  3. overdose causes skeletal muscle twitching, clonic convulsions, respiratory depression, and death
  4. toxicity can be treated with general anestetics (eg barbituates) and diazepam, and respiratory support
A
  1. no (exception… cocaine)
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14
Q

(PNS)

  1. high doses are neurotoxic and may cause what?

(Methemoglobinemia in cats)

  1. esp following what?
  2. what happens to hemoglobin?
  3. what is main clinical sign?

(Hypersensitivity)

  1. What two reactions?
A
  1. permanent sensory loss
  2. tetracaine or benzocaine
  3. oxidation from ferrous (FE2) to ferric (Fe3) - binds water instead of oxygen
  4. cyanosis (blue or purple skin due to low blood oxygen)
  5. asthmatic and anaphylactic
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15
Q

gander

A
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16
Q

(Characteristics of some local anesthetics)

(esters)

(cocaine) (eg in TAC - pediatric medicine: tetracaine, adrenaline, cocaine)
1. historical prototype drug
2. vasoconstrictor; CNS stimulant; blocks reuptake of what and what?

A
  1. NE and serotonin
17
Q

(esters)

(Procaine (Novocain) - not in CVM)

  1. first synthetic LA
  2. what percentage aqueous solution for infiltration and nevre block?
  3. affect on heart?
  4. how long does it act?
  5. What is the cause of most allergies to procaine?
A
  1. 0.5-2%
  2. antiarrhythmic
  3. short duration of action
  4. PABA (metabolite that interferes with action of sulfonamide antibiotics)
18
Q

(esters)

(tetracaine - pontocaine)

  1. how potent vs procaine and cocaine?
  2. used in opthalmology and for tissue infilitration
  3. how long is duration of action?
  4. how often used? why?
A
  1. 10X
  2. long
  3. seldom, delays post surgical healing
19
Q

(Esters)

(Proparacaine (ophthaine))

  1. similar to tetracaine, but no tissue irritation
  2. 0.5% ophthalmic solution
  3. useful in corneal ulcer cauterization, foreign body removal from eye

(Benzocaine)

topical anesthetic common in ointments and sprays… long acting

poor solubility in water, less toxis

A
20
Q

(Amides)

(Lidocaine - xylocaine - THE ONE TO REMEMBER)

  1. most commonly used (infiltration, nerve block, and epidural)
  2. how potent and toxic relative to procaine?
  3. used how in heart treatment?
  4. how long is duration of action?
A
  1. 2X more potent, more toxic
  2. useful in treating arrythmias
  3. medium
21
Q

read

A

answer

004 - Neuropharmacology (11 decks)

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