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Pharmacology > Ch 25: General Anesthetics > Flashcards

Ch 25: General Anesthetics Flashcards

1
Q

General Anesthetics

A 
useful for rendering patients that are unable to experience pain during procedures:
surgical
obstetric
therapeutic
diagnostic
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2
Q

General Anesthetic produce an unconscious state

A
  1. Depress the CNS
  2. Depress CV system
  3. Depress Respiratory System
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3
Q

Depress the CNS

A
  1. Loss regulatory mechanisms
    a. thermoregulation
    b. baroreceptor reactivity
  2. respiratory
  3. Lose protective mechanisms
    a. glottic reflexes
    b. position injuries
  4. corneal abrasions
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4
Q

Depress CV system

A
  1. Decreased contractility
  2. Peripheral vasodilation
  3. Reduced organ perfusion
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5
Q

Depress Respiratory system

A
  1. Induced Hypoxemia

2. Cause retention of secretions (pneumonia)

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6
Q

Why do we use general anesthesia?

A 
Patients want to be sleep
patients are uncooperative
can't use a regional anesthesia
produce amnesia
produce analgesia
promote muscle relaxation
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7
Q

4 stages of general anesthesia

A

analgesia excitement
surgical anesthesia
medullary paralysis

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8
Q

analgesia

A

somewhat conscious

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9
Q

excitement

A

unconscious & amnesic, but agitated & restless

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10
Q

surgical anesthesia

A

slow, deep breathing, muscle relaxation

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11
Q

medullary paralysis

A

breathing stops, CV collapse…. need support for life

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12
Q

Inhaled agents

A 
potent
rapid induction & recovery
muscle relaxant
non-irritating to airway
no excess CV depression
suppresses excessive sympathetic activity
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13
Q

Types of inhaled agents

A

gases

volatile liquids

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14
Q

gases

A

traditionally ether & chloroform, now only nitrous oxide (N2O)

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15
Q

volatile liquids

A

halothane
isoflurane
desflurane
sevoflurane (newest)

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16
Q

Inhaled agent pharmacokinetics

A
  • must reach a therapeutic tissue concentration in the brain
  • highly lipophilic
    (will get widely distributed throughout body)
  • Induction & recovery time increased in obese patients (adipose “sink”)
  • recovery is based on respiratory, CV. and metabolic rates
17
Q

pharmacokinetics

A

drugs moves from machine to lungs, to blood, to CNS circulation, to local sites

Induction time based on:

  • conc. of drub, pressure of system, response rate
  • solubility of gas, CO, pressure gradient
  • solubility into brain tissue, blood flow into tissue, artery to vein pressure difference
18
Q

reversal of anesthesia

A
  • turn vaporizer to “0” & hyperventilate
  • most leaves unmetabolized through lungs
  • if needs to be metabolized, liver function is important in recovery time
  • circulation effects speed of drug movement
19
Q

General Perturbation Theory

A
  • works by disrupting membranes
    • potency correlated w/ lipid solubility
    • similar effects for a variety of chemical structures
    • presumable “squeeze” membranes to slow ion flux
    • general phenomena throughout brain
20
Q

Specific Receptor Theory

A
  • bind to receptor sites or ion channels to slow Na+ influx
  • related to lipophilicity
  • variety of ion channels & receptors (GABA-a & NMDA)
21
Q

reduced neurotransmission

A
  • may cause strengthened inhibition/ reduced excitation

- a greater effect on excitatory transmission than inhibitory

22
Q

inhaled agent side effects

A
  • cv depression
  • decreased B.P & H.R.
  • depressed airway reflexes (cough)
  • bronchodilator (good for asthma & emphysema)
  • decreased ciliary action (retain secretions)
  • reduced ability to speed up respiration following hypoxia & hypercarbia
  • may enhance potency
  • likely to reduce side effects of either
23
Q

intravenous agents

A

used for induction of anesthesia

from stage 1 to 3 quickly

24
Q

IV agents used

A 
thiopental 
midazolam
propofol
ketamine
etomidate
25
Q

sodium pentathol (thiopental)

A
  • depress RAS
  • ultra short acting Barb (30 sec hypnosis)
  • last 5-10 mins (mostly for induction)
26
Q 
side effects of
sodium pentathol (thiopental)
A 
cv depression (prob. w/ heart disease patients)
respiratory depression (significant)
risk stage 2 if adequate dose
27
Q

Propofol

A
  • presumed GABA-a action
  • quick induction
  • rapid recovery (even w/ sustained infusions)
  • hypnotic but not analgesic
28
Q

side effects of propofol

A

similar to Pentothal

fast or slow heart rate
high or low blood pressure
injection site reactions (burning, stinging, or pain)
apnea
rash
itching
29
Q

Ketamine

A
  • binds NMDA receptor, inhibits glutamate action
  • dissociates thalamus from limbic system
  • patient appears conscious, but unable to respond to stimulus (dissociative anesthesia)
30
Q

side effects of ketamine

A
  • Cardiovascular
    ** increased B.P & C.O
    (avoid in patients w/ arterial disease, hypertension, aneurisms)
  • Respiratory
    • minimally affected (good for asthmatics)
  • CNS
    • analgesic = good for short procedures
  • strong hallucinogen (kids like, but not adults)
31
Q

Etomidate

A
  • depress RAS
  • simian to pentothal in kinetics
  • reduce respiration
  • minimal CV effects (hypnotic, not analgesic)
  • disinhibits extrapyramidal motor centers (myoclonic movements)
32
Q

adjuvants

A
  • to sedate/ calm
    • pentobarbital (barbs)
    • morphine/ meperidine (opioids)
    • diazepam/ lorazepam (Benzos)
    • diphenhydramine/ promethazine (anti-hist)
    • Neuromuscular junction blockers
  • ——–gallamine, pancuronium, succinylcholine

Pharmacology (17 decks)

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