General and Local Anesthetic Drugs Flashcards

1
Q

Anesthetics primarily act on the… (2)

A

Synapse:

  • presynaptic: release of NTs.
  • postsynaptic: frequency/amplitude of impulses exciting the synapse.
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2
Q

What inhibitory channels do general anesthetics activate? (2)

A

Cl- channels (GABA-A and glycine receptors).

K+ channels.

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3
Q

What excitatory channels do general anesthetics inhibit? (3)

A

AChR (mAChR and nAChR)
EAA (AMPA, kainite, NMDA)
Serotonin

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4
Q

What is the “driving force” for uptake of inhaled anesthetics?

A

Alveolar concentration, which is driven by inspired air concentration and alveolar ventilation.

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5
Q

What is the blood:gas coefficient?

What is the relationship between the coefficient and rate of anesthetia onset?

A

It defines the relative affinity of an anesthetic for the blood compared with that of inspired gas (i.e. blood solubility).

Inverse - agents with low blood solubility reach high arterial pressure very quickly, and vice-versa.

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6
Q

What is the blood:brain coefficient?

Does this vary much between drugs?

A

It defines the relative affinity of an anesthetic for the brain compared to blood.

It is relatively similar for all inhaled anesthetics; anesthetics are more soluble in the brain.

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7
Q

What is the blood:gas partition coefficient, brain:blood partition coefficient and MAC for NO?

A

Blood:gas - 0.47 (low)
Brain:blood - 1.1 (low)
MAC - >100% (high)

Incomplete anesthetic; rapid onset and recovery.

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8
Q

What is the blood:gas partition coefficient, brain:blood partition coefficient and MAC for Halothane?

A

Blood:gas - 2.3 (high)
Brain:blood - 2.9 (high)
MAC = 0.75% (low)

Medium rate of onset and recovery.

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9
Q

What is MAC?

What is meant by a MAC >100%?

How much MAC in NO is sufficient for surgical anesthesia for most people?

A

Minimal Alveolar Concentration = measurement of anesthetic potency.

MAC >100% = if 100% of inspired air is the anesthetic, less than 50% of subjects would be anesthetize and other agents are needed to achieve full surgical anesthesia.

Using NO to produce 40% MAC in combo with 70% of a volatile agent’s MAC would equal 110% MAC and is sufficient in most people.

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10
Q

What are the common side-effects of inhaled anesthetics?

What side-effect is specific to Halothane?

Which agents may cause renal toxicity?

A

Nausea and vomiting.

Hepatitis: symptoms onset within 2 days to 3 weeks after exposure (nausea, myalgia, rash, eosinophilia, jaundice and elevated LFTs).

Agents that are metabolized to products including fluoride ions (enflurane and sevoflurane).

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11
Q

What causes malignant hyperthermia?

What is the antidote?

A

Succinylcholine in combo with volatile anesthetics may cause malignant hyperthermia.

Dantrolene.

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12
Q

IV anesthetics are the preferred mechanism of anesthesia is most cases because…

A

They are highly lipophilic and preferentially partition into highly perf used lipophilic tissues (brain and spinal cord) - quick onset of action.

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13
Q

What are the important IV anesthetic drugs? (5)

A
Etomidate
Ketamine
Midazolam
Propofol
Fentanyl
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14
Q

Which IV anesthetics are known to have a slow onset? (2)

A

Midazolam

Fentanyl

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15
Q

Which IV anesthetics are considered to have a rapid onset? (2)

A

Etomidate

Propofol

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16
Q

Which IV anesthetic drug is considered to be moderately rapid in onset? (1)

A

Ketamine

17
Q

What is the MOA of Propofol?

What is Propofol made from?

Which adverse-effects may ensue? (3)

A

Targets GABA-A and acts as an agonist.

It is an emulsion with soybean oil, glycerol and lecithin (egg yolk component).

Allergic reactions (due to lethicin), hypotention and respiratory depression.

18
Q

What is the MOA of Etomidate?

How does its rate of LOC and recovery rate compared to Propofol?

Which patients is it useful to use?

What are the usual adverse-effects? (1)

Why is it rarely used via continuous infusion?

It undergoes…

A

Enhances actions of GABA on GABA-A receptors.

Patients with poor CV +/- respiratory symptoms because it causes minimal CV and respiratory depression.

Endocrine: adrenocortical suppression by inhibiting 11b-hydroxylase (cholesterol to cortisol conversion).

4-8 hour suppression after induction limits its usefulness for continuous infusion.

Extensive liver and plasma biotransformation.

19
Q

What is the MOA of Ketamine?

What does it cause?

What does it stimulate?

It is the only IV anesthetic to…

A

NMDA-receptor antagonist; similar to PCP.

Dissociative anesthetic state: catatonia, amnesia, analgesia +/- LOC.

Stimulates the SNS.

Produce profound anesthesia.

20
Q

What is the MOA of Dexmedetomidine?

Its sedative effect resembles…

What is used for mostly?

A

Alpha-2 adrenergic agonist in the locus caeruleus and spinal cord.

It resembles a physiologic sleep state.

Short-term sedation of incubated and ventilated patients in the ICU or as an adjunct to general anesthesia.

21
Q

Which drug classes are considered to be anesthesia adjuncts? (3)

A

Opioids
Barbiturates
Benzodiazepines

22
Q

What is the general MOA of local anesthetics?

What chemical classes are these drugs? (2)

A

Blockage of voltage-gated Na+ channels and inhibit the spread of APs across nerve axons.

Amides (if the drug name has > 2 “i’s” the drug is an amide).
Esters (1 “i”)

23
Q

What are the 2 major forms of adverse-effects of local anesthetics?

What are adverse-effects in the following?
CNS (high vs. low concentrations)
CV
Allergy

A

Toxicity following systemic absorption + direct neurotoxicity.

CNS: sleepiness, light-headedness, visual/auditory disturbances (low conc.); nystagmus, fasciculations, convulsions (high conc.; may pre-medicate w/ benzo).
CV: decrease CV conduction rate, force of contraction and arteriolar dilation leading to systemic hypotension.
Allergic: reactions to ester-types are most common due to metabolism of allergy-causing compounds.

24
Q

Benzocaine is used on as a…

A

Topical agents - poor water solubility.

25
Q

Bupivacaine is used for…

A

Producing prolonged anesthesia.

26
Q

Cocaine is used for…

A

Topical anesthesia of the URT.

27
Q

Dibucaine is only available as…

A

A topical cream for skin use due to its toxicity associated with injection.

28
Q

Procaine is primarily used for…

A

Infiltration anesthesia (local anesthesia produced by injection of the anesthetic solution directly into the area of terminal nerve endings).

29
Q

What are the inhaled anesthetics? (6)

A
Desflurane
Isoflurane
Enflurane
Sevoflurane
Halothane
NO
30
Q

What about Propofol’s PKs makes it a good choice for IV anesthesia?

A

Averages 30 sec onset of action and has a 3-10 min duration of action (dose-dependent).
There is also rapid recovery and patients are able to ambulated shortly after use.
Its PKs allow for short-duration general anesthesia (outpatient possible) as well as continuous infusion and sedation (ICU setting).