Exam 3 - Lecture 27 & 28 General anesthetics, anxiolytics & sedatives, hypnotic drugs Flashcards

1
Q

General anesthetics

A

Can induce a state of systemic anesthesia, lack of feeling

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2
Q

Anxiolytics

A

reduce anxiety

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3
Q

Sedatives (tranquillizers)

A

CNS depressants that induce calm

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4
Q

Hypnotics (soporifics or sleeping pills)

A

Typically psychoactive drugs that induce sleep

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5
Q

Modes of Drug delivery Anesthetics

A

Inhalation or injection

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6
Q

What is MAC

A

MAC - Minimum alveolar concentration, equivalent of potency

The lower the MAC, more potent the anesthetic

MAC is ~20% higher in red heads, due to mutations in melanocortin-1 receptor

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7
Q

Moving MAC curve left

A

Hypoatraemia (low sodium), increased age, pregnancy, opioid use, benzo, intoxication

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8
Q

Moving MAC curve right

A

Chronic amphetamine, cocaine, ephedrine, chronic alcohol use, decreased age

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9
Q

MAC: Zur Theorie def Alkoholnarkose Arguments for

A

Simple, diverse structures argues against obvious SAR

Suggest physicochemical mechanisms of action;
Bilayer thickness, curvature, fluidity

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10
Q

MAC: Zur Theorie def Alkoholnarkose Arguments against

A

Stereoisomers have similar oil:gas partition coefficients but different MAC

Many lipophilic drugs are not anesthetics

Change in body temp alter membrane fluidity but is not anesthetic

Changes in chain length increase lipophilicity but not MAC

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11
Q

Using EEG to measure anesthesia?

A

Distinction between anesthesia and sleep

If sleeping you can be arousable but if you’re anesthetized then you are unarousable.

Nonphysiological Oscillations in anesthesia
physiological Oscillations in Sleep

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12
Q

MAC value

A

The lower the better it will cross from Alveoli, into blood and then into Brain.

For example, drug with MAC 0.47 will cross better than one with a MAC of 2.3

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13
Q

Other considerations besides MAC for potency

A

The age and life-style of the patient
How fat
Other medications
Hair color

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14
Q

Blood/Gas partition coefficients and induction/recovery rate

A

The lower the blood/gas partition coefficient, the faster the induction of effect and recovery rate

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15
Q

Effect of isoflurane on Nav Channels

A

Inhibiting Nav channels in CNS neurons reduces excitability

Concentration dependent,

decreasing excitability in the brain

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16
Q

Effects on K2P channels

A

Activating K2P channels in CNS neurons reduces excitability

Open channel = less excitability, decreasing epilepsy and increasing anesthesia effects

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17
Q

K2P channel structure

A

not voltage gated

2 subunits

Subunit made of 4 Transmembrane proteins, 2 P loops

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18
Q

Ether

A

Cheap & easy to make, no longer recommended by WHO

MoA:
Positive Allosteric modulator at GABAa receptor
Agonist at GABAa-receptor at higher dose

Sympathomimetic effect, maintains BP

Side effect:
Post operative nausea and vomiting
Seizures and tremors

V flammable and explosive mixed with Oxygen

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19
Q

Nitrous Oxide

A

Laughing gas, non-flammable roomtemp

MAC >100%

Fast acting, can cause euphoria

MoA:
Weak PAM of GABAa and glycine receptor
Weak activator K2P, blocker NMDA, AMPA, kainite and GABAc

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20
Q

Halothane (fluothane)

A
MoA:
#1 - Agonist at GABAa receptors
Agonist at glycine receptors
Antagonist at NMDA receptors and Nav channels
Activates K2P channels

Side effect:
Arrhythmia
Respiratory depression
Hepatoxicity (metabolized into trichloroacetic acid = 30-70% mortality)

Not used in US anymore

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21
Q

Isoflurane (forane)

A

Widely used, non explosive

MoA:
#1 Agonist at GABAa receptors
Agonist at glycine receptors
Antagonist at NMDA receptors and Nav channels
Activates K2P channels

side effect:
Cardiac arrhythmia
Respiratory depression

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22
Q

Sevoflurane (Ultane, sojourn)

A

widely used, expensive bc hard to make

MoA:
#1 Positive allosetic modulator at GABAa (and GlyR?) receptors
NMDA receptor antagonist
Activated K2P channels

side effect:
Amongst safest agents available
All gas anesthetics associated with neurotoxicity
Neurodev/behavior abnormalities in kids?

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23
Q

Etomidate change % in BP/Heart Rate

A
  • BP (low, ~2%)/ + Heart Rate
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24
Q

Injectable Anesthetics

A

More potent than gas ones

Not appropriate for long surgery, often used to induce anesthesia

25
Q

Sodium Thiopental

A

Barbiturate sedative/anesthetic injection

Rapid onset (20-45s) and rapid recovery (<10Min) very short acting

Used to break status epileptics

increases open time of GABAa receptor channels

“truth serum”, used Euthanasia

distributes into greasier tissues due to its greasiness

26
Q

Methohexital (Brevital)

A

Used for ECT, lowers threshold for seizures but other anesthetics must be used to break seizures

Used to induce anesthesia, fast recovery

Increase open time of GABAa receptor channels

27
Q

Methohexital (Brevital)

A

Used for ECT, lowers threshold for seizures but other anesthetics must be used to break seizures

Used to induce anesthesia, fast recovery

Increase open time of GABAa receptor channels

28
Q

Propofol (milk of amnesia)

A

Most used induction agent

Anti emetic, and anti seizure…often used to break induced seizures or status epileptics

MoA:
Positive allosteric modulator at GABAa receptors, Nav channel blocker

Side effect:
Drop BP
Cause irregular breathing
Pain at injection site
Vasodilation - have to give with a drug to bring BP up
29
Q

Etomidate

A

R 10X more potent than S

Used in pt where history unclear/ BP is unstable

MoA:
PAM at B2, B3 GABAa receptors
GABAa receptor agonist at higher conc

side effect:
Adreno-cortical insufficiency = lower cortisone production and more susceptible to infection

Paradoxical effect = causes opposite effects of what is usually seen

30
Q

Ketamine

A

Commonly used Europe for Off-site trauma..not much US

MoA:
NMDA-R antagonist with low potency effects at many other sites, including nAChRs and d and mORs = reduce excitation

Side effect:
Altered heart rhythms
Hallucination
Adverse drug interactions

Potential for depression treatment but also drug of abuse

31
Q

Ketamine treat depression?

A

Ketamine is a dissociative anesthetic - make patient feel removed from their problems

32
Q

Esketamine (Spravato)

A

metabolite of ketamine

MoA:
Non-competitive antagonist at NMDA-receptor

Suitable for induction in patients with hemorrhagic, anaphylactic or septic shock

33
Q

Why regional anesthesia better?

A

Cheaper
Fewer post-op issues

Patient can be fully awake or sedated

no risk of general anesthesia

Decreased chance of DVT

No drug-drug considerations

34
Q

Why regional anesthesia better?

A

Cheaper
Fewer post-op issues

Patient can be fully awake or sedated

no risk of general anesthesia

Decreased chance of DVT

No drug-drug considerations

35
Q

Xenon

A

MoA:
Antagonist at NMDA receptor ( no hallucination on emergence)

Side effects:
Very expensive….recycle?( isn’t altered via metabolism)
Minimal, including no nausea

36
Q

Methoxycarbonyl - Etomidate

A

Removes the decrease in cortisone
Keeps rapid onset of etomidate
Maintain hemodynamic stability of etomidate

Rapid metabolism by esterase’s into etomidate, causing decrease cortisone later

37
Q

Long acting Benzo

A

Diazepam
Chlordiazepoxide
Chlorazepate
Flurazepam

Long acting = many active metabolite formed

38
Q

Intermediate acting Benzo

A

metabolized into glucuronides often, not usually active

Alprazolam
Lorazepam
Oxazepam
Temazepam
Clonazepam
Estazolam
Quazepam
Clobazam
39
Q

Short acting Benzo

A

Hydroxylated and eliminated fast relatively

Midazolam
Triazolam

40
Q

Alprazolam (Xanax)

A

Triazolobenzodiazepine - Triazole ring stops it from having same metabolism as diazepam

Used for:
Anxiety + panic attacks
Chemo nausea

side effect:
Sleepy, depression, memory problems
Drug of abuse

41
Q

Diazepam (valium)

A

classic sedative

High chance for abuse and addiction, OD common due to street version of drug

Side effect:
Can change brainwave patterns, where patient uses it to sleep but then it’ll cause worse sleep

impair motor function, coordination and balance…in cerebellum

42
Q

Midazolam (versed)

A

Commonly used in ICU/ critical care med

Has diazole ring preventing diazepam metabolism pathway

Most hydrophilic BDZ so can be used in saline infusion

Used for people on vent, not much anymore

Used for deep sedation of patients who are suffering and end of life care.

Used as sedative for euthanasia

Side effect:
Paradoxical reaction
Amnesia
Tolerance and dependence
OD possible
43
Q

Mechanism of tolerance/addiction Benzos

A

Increase GABA signaling decreases receptor density (increase amount internalized or decrease amount brought to membrane)

Leads to equilibrium between higher conc of GABA and lower receptors

Decrease GABA conc (withdrawal) and GABAergic inhibition of excitability is lost

44
Q

Alcohol Withdrawal syndrome

A

Minor Withdrawal: Onset 6 - 36 hrs last drink
Seizures: Onset 6 - 48 hrs last drink
Alcoholic hallucinosis: Onset 12 - 48 hrs
Delirium tremens: Onset 48 to 96 hrs

45
Q

Alcohol Withdrawal syndrome treatment

A

preference is long-lasting benzo (Diazepam)

In patients with cirrhosis or acute alcohol hepatitis then Lorazepam is preferred

46
Q

Benzo bind to which subunits

A

Between alpha and gamma, increase open frequency (number of times open)

47
Q

Barbiturate bind to which subunits

A

Between alpha and beta, increase amount of time each time it opens

48
Q

Pentobarbital (Nembutal)

A

Used for euthanasia, Human (execution) and vet

Sedative, hypnotic, short term anesthetic

Active metabolite of thiopental

Potential for OD

Street drug - yellow jackets

Can give Thiopental, gets metabolized into pentobarbital but then harder to predict how much you are giving in terms of dose

49
Q

Meyer-Overton correlation for anesthetics

A

The lower the Mac value (more potent) the higher the Oil:gas partition coefficient (more lipophilic)

50
Q

MAC Mechanisms of action

A

Easier something partitions into brain, faster it works

51
Q

How to measure Mac

A

Measured at sea level due to pressure

After 15 minute equilibration

By end-tidal volume of the gas

52
Q

Mac partition

A

Quickest partition between arterial blood and brain

Over time it will leave brain to try and reach equilibrium with other tissues

53
Q

Multimodal

A

Multiple low affinity receptor targets with complimentary effects

54
Q

Phencyclidine (PCP)

A

antagonist NMDA receptor
Agonist D2 and sigma2

associated with hallucination

dissociative anesthetic

55
Q

Thiopental % change in BP/HR

A

-8%, +14%

56
Q

Methohexital % change in BP/HR

A

-8%, +15%

57
Q

Propofol % change in BP/HR

A

-17%, +8%

58
Q

Ketamine % change in BP/HR

A

+28%, +33%