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NMSK Exam 3 > General Anesthetics > Flashcards

General Anesthetics Flashcards

1
Q

Inhalaled Anesthetics

A

Volatile anesthetics (liquid at room temp; high boiling point)

  1. Desflurane
  2. Enflurane
  3. Halothane
  4. Isoflurane
  5. Sevoflurane

Gaseous anesthetics (gas at room temp; low BP)

  1. Nitrous oxide
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2
Q

Volatile anesthetics end in which suffix?

A
  • -ane
  • Halothane, enflurane, isoflurane, desflurane, and sevoflurane
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3
Q

IV anesthetics (6)

A
  1. Diazepam
  2. Etomidate
  3. Fentanyl
  4. Ketamine
  5. Midazolam
  6. Propofol
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4
Q

What effects do General Anesthetics produce?

A

Anesthetic state

  1. Unconsciousness
  2. Amnesia
  3. Analgesia
  4. Attenuation of autonomic reflexes
  5. Immobility
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5
Q

What general anesthetics produces a anesthetic state?

A

No single drug acheives all 5 sates; must use combo of IV + inhalaled drugs (balanced anesthetia)

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6
Q

How do inhaled anesthetics distributed T/O the body?

A

Absorbed via gas exchange into alveoli => blood => body

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7
Q

MOA of general anesthetics

A
  1. Facilitate Cl- channels via GABA-A or glyceine
  2. DEC + of excitatory channels => nAChR/mAChR, AMPA, Kainate, NMDA
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8
Q

Rate at which an inhaled anesthetic is absorbed depends on what?

A
  1. Concentration of anesthetic in inspired air

1. Ventilation rate

3. Solubility in air, blood and CNS

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9
Q

Induction of anesthetia is slower with ______ soluble anesthetic gases

A

More soluble inhaled anesthetic = SLOWER onset

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10
Q

What is the Blood:gas partition coefficient and how does it relate to an anesthetics onset of action?

A
  • Defines relative affinity of an anesthetic for the blood compared to inspired gas (i.e., blood solubility)

- Inverse relationship btw blood:gas partition coefficient values and rate of onset of drug

  • Drugs w/ ↓ blood : gas coefficient =>
  • less soluble in blood (NO, desflurane) =>
  • rapid rise in arterial pressure
  • => rapidly equilibriate with brain
  • => fast onset of action
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11
Q

How does the value of minimum alveolar concentration (MAC) relate to potency?

A

↓↓↓ MAC = ↑↑↑ potent

*Inverse relationship

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12
Q

Drugs with high blood:gas coefficient => _____ blood solubility => ____ increase in arterial partial pressure => ____ equilbriation with brain => ____ onset of action

A
  • more soluble in blood
  • slow
  • slow
  • slow
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13
Q

What is the brain: blood parittion coeffcient for inhaled anesthetics?

A

Relatively similar for all inhaled anesthetcs => _more soluble in brain t_han blood.

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14
Q

Why is the induction of anesthesia slower in more soluble gases?

A
  1. Takes longer for the blood partial pressure of the moer soluble gas to rise to the same partial pressure as in the alveoli
  2. Bc concentration of the anesthetia in the brain CANT rise faster than in the blood =>slower onset
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15
Q

What parts of the body do inhaled anesthetics MOST go to and why?

A

Brain, heart, liver, kidney and splanchnic bed: bc get 75% of CO.

*accumulate slowly in skin and muscle bc only get 1/2 of CO

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16
Q

which inhaled anesthetics are eliminated from the body the fastest?

A

Those relatively insoluble in blood and brain.

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17
Q

How are inhaled anesthetics elimated from the body?

A

Lungs; but some are metabolized by liver

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18
Q

What does the MAC correspond to on the drug-dose effect curve?

A

ED50

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19
Q

Which inhaled anesthetic may have a toxic side effect of hepatitis (hepatomegaly, jaundice, and liver tenderness) which can present 2 days to 3 weeks after exposure?

A

Halothane

‘H’ for Hepatoxicity

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20
Q

Which toxicity is associated with the inhaled anesthetics, Enflurane and Sevoflurane?

A

Renal toxicity due to fluorinated metabolites

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21
Q

In combination with succinylcholine, inhaled VOLATILE anesthetics may cause what serious adverse reaction?

What is seen with this reaction?

A

- Malignant hyperthermia

  • - Rapid onset tachycardia and HTN
    • Severe muscle rigidity
  • rhabdomyolysis,
  • hyperthermia,
  • hyperkalemia,
  • acid-base imbalance w/ acidosis
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22
Q

What is the antidote for malignant hyperthermia?

A

Dantrolene

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23
Q

What is meant by the term “balanced anesthesia?”

A
  • Modern anesthesia relies on the use of combos of IV and inhaled drugs to take advantage of the favorable properties of each drug, while minimizing adverse effects
  • No single available drug can achieve all 5 desired effects of the anesthetic state
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24
Q

Define minimum alveolar concentration (MAC)?

A
  • Concentration of inhaled anesthetic that prevents movement during surgery in 50% of ppl (meausre of potency; ED50)
  • This is equal to 1 MAC
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25
Q

1 MAC =

A

50% of population will not move to skin stimulation during surgery

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26
Q

Which inhaled anesthetic has a MAC (vol %) >100 and what does this mean for use in surgery?

A

Nitrous oxide

  • >100% indicates that if 100% of inspired air is the anesthetic, the MAC value would still be <1 and other agents must be given to achieve full surgical anesthesia
  • You can’t achieve >100% nitrous oxide; you couldn’t achieve 80% either w/o killing the patient!
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27
Q

What is the MAC of: Desflurane, Sevoflurane, Isoflurane, Enflurane, and Halothane?

Which is the least and most potent?

A
    • Desflurane = 6-7% (least potent)
    • Sevoflurane = 2%
    • Isoflurane = 1.4%
    • Enflurane = 1.7%
    • Halothane = 0.75% (most potent)
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28
Q

How do inhaled volatile anesthetics affect CV system?

Specific effects related to halothane, desflurane and isoflurane?

A
  1. - ↓↓↓ MAP in direct proportion to their alveolar concentration
    • ↑↑↑ right atrial pressure, due to depression of myocardial function
    • Halothane can cause bradycardia
    • Desflurane and Isoflurane can ↑↑↑ HR
29
Q

Which property of IV anesthetics accounts for their quick onset of action?

A

Highly lipophilic and preferentially partition into highly perfused lipophilic tissues (brain, spinal cord)

30
Q

Inhaled volatile anesthetics affect respiration how?

A

Respiratory depression

31
Q

What is the most likely MOA of Propofol?

A

GABA-A R AGO : potentiates the Cl- current

32
Q

Describe the pharmacokinetics of Propofol (i.e., metabolism, rate of onset and recovery)

A
  • Rapidly metabolized in liver (phase I and II rxns) w/ extensive extrahepatic metabolism (i.e., lung may account for elimination of up to 30% of a bolus dose)
  • Rapid rate of onset= 15-30 seconds
  • Rapid recovery, patients able to ambulate quickly (low hangover effect)
33
Q

What is Propofol mainly used for based on its PK?

A
  1. Induce and maintain anesthesia; can be continously infused
  2. Sedation in ICU
  3. Conscious sedation
  4. Short-duration general anesthesia outside OR (i.e., interventional rads., ED, and dental offices)
34
Q

Which IV anesthetic has poor solubility in water and is an emulsion that contains soy bean oil, glycerol, and lecithin; making allergic reactions a possibility in susceptible patients?

A

Propofol

35
Q

What is context-sensitive 1/2 life?

Which drugs have dramatic increases in 1/2 life (context-sensitive 1/2 life) with prolonged infusions?

A

After prolonged infusion, the drugs 1/2 life depends on:

  1. Rate of re-distrubition on the frug
  2. Amount of drug that accumalted in fat
  3. Drugs metabolic rate.
  4. - Diazepam
  5. - Thiopental
36
Q

Compared to other IV anesthetics which drug produces the most pronounced decrease in systemic BP (HYPOTENSION) due to profound vasodilation in both arterial and venous circulation leading to r_eductions in preload and afterload?_

A

Propofol

37
Q

What are the respiratory effects of Propofol?

A

Profound respiratory depression

38
Q

What are the CNS effects of Propofol?

A
  1. Supress CNS, but can cause twitching and spontaneous movement when inducing.
  2. ↓ ICP/IOP because ↓ cerebral blood flow and metabolic rate for O2.
  3. NO analgesic properties
39
Q

Common AE for Propofol?

How do we avoid?

A

Pain when injecting; give opioid or lidocaine before

40
Q

What is Fospropofol and how is it metabolized?

A

Water-soluble PROdrug of propofol that is rapdily metabolized by alkaline phosphatase (ALP)

41
Q

What are common adverse effects of Fospropofol?

A
    • Paresthesias (including perineal discomfort or burning sensation)
    • Pruitis/itching (including genital, perineal, and generalized pruritus)
42
Q

What are the differences and advantages of using Fospropofol?

A
    • Effects are similar to Propofol, but onset and recovery are prolonged, since prodrug needs to be metabolized
  2. - Water soluble
  3. - Less pain on administration
43
Q

What is the MOA of the IV anesthetic, Etomidate?

A

Enhances the actions of GABA on GABA-A R =>

Hypnotic, but NOT analgesic effects

44
Q

Which patients would it be useful to use Etomidate in, why?

A
  • Those with impaired CV and respiratory systems
  • Causes minimal CV and respiratory depression
45
Q

What are the CNS effects of Etomidate?

A

Potent cerebral vasoconstictor; ↓↓↓ cerebral blood flow and ICP

46
Q

What is significant about the CV effects of the IV anesthetic, Etomidate?

A

CV system stability; minimal change in HR and CO

47
Q

Which IV anesthetic causes adrenocortical suppression by producing dose dependent inhibition of 11β-hydroxylase (necessary to convert of cholesterol => cortisol)?

A

Etomidate

*Think Etomidate = Endocrine Effects!

48
Q

What is the MOA of Ketamine?

A

NMDA- R ANT =>

  • Dissociative anesthetic state (catatonia + amnesia + analgesia) with or w/o LOC (eyes stay open with slow nystagmic gaze)
49
Q

What are the MAIN limiting factor for use of Ketamine?

A
  • Unpleasant emergent reactions after administration: vivid colorful dreams, hallucinations, etc); can
  • Can also cause euphoria => abusive
50
Q

What is the only IV anesthetic to produce

  1. profound analgesia,
  2. stimulation of the sympathetic nervous systm,
  3. bronchodilation,
  4. minimal respiratory depression?
A

Ketamine

51
Q

What are the effects on the CV system by Ketamine?

A

+ sympathetic NS => Increase systemic BP, heart rate, and CO;

52
Q

Ketamine is not recommended in patients with which pathology, due to what effects?

A

- Intracranial pathologies bc

- ↑↑↑ cerebral blood flow and ICP

53
Q

Which inhaled anesthetic has thw loest and highest blood:gas partition coefficient?

A
  1. NO = 0.47 = less soluble in blood = rapid onset
  2. Halothane = 2.3 = more soluble in blood = medium onset and reovery
54
Q

Which inhaled anesthetic is a incomplete anesthetic with rapid onset + recover?

A

Nitrous oxide

55
Q

Which anesthetic has low volatility, poor induction agent but has RAPID recovery?

A
  1. Desflurane
56
Q

Which inhaled anesthetic has rapid onset + recovery?

A

Sevoflurane

57
Q

Which inhaled anesthetics have MEDIUM rate of onset + recovery?

A
  1. Isoflurane
  2. Enflurane
  3. Halothane
58
Q
  1. 4 common IV opioid analgesics used as anesthetic adjuncts: augments specific components of anesthesia => lower doses of general anesthesia
  2. MOA?
A

Fentanyl, Sufentanil, Remifentanil, Morphine

- Opioid-R AGO

59
Q

What are the 2 IV Barbituate anesthetics used as adjuncts?

A

- Thiopental (prototype)

- Methohexital

60
Q

Which IV Barbituate is preferred for short ambulatory procedures due to its rapid elimination?

A

Methohexital

61
Q

Which anesthetic adjuncts induce CYP450 enzymes?

A

Barbituates —> Thiopental and Methohexital

62
Q

What are the 3 common IV Benzodiazepines used as anesthetic adjuncts?

A
  1. Diazepamn
  2. Lorazepam
  3. Midazolam
63
Q

What is the MOA of IV Benzodiazepines used as anesthetic adjuncts

A

Act on GABAA receptor allosteric modulators => increase sensitivity to GABA (agonist) and enhances inhibitory neuotransmission

64
Q

IV Benzodiazepines used as anesthetic adjuncts are commonly used when and why?

Actions can be terminated by which antagonist?

A

- Perioperative period: anxiolytic and cause anterograde amnesia

  • Can be terminated by the antagonist, flumazenil
65
Q

Which IV Benzodiazepine used as an anesthetic adjunct is water-soluble and considered the drug of choice for parenteral administration?

What else is unique about this specific benzo?

A
  • Midazolam = water soluble (others are not)

- Given IV before entering OR bc;

  1. More rapid onset
  2. Shorter 1/2 life (2-4 hrs)
  3. Steeper dose-response curve
66
Q

Benzodiazepines have potent __________ properties; used in the Tx of status epilepticus, alcohol withdrawl, and local anesthetic-induced seizures

A

Anticonvulsant

67
Q

Which IV anesthetic provides CV stability; causes decreased steroidogenesis and involuntary muscle movements?

A

Etomidate

68
Q

Which IV anesthetic is used as a standard induction agent, but must be avoided in porphyrias?

A

Thiopental

NMSK Exam 3 (17 decks)

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