Ch 25: General Anesthetics

Question 1

General Anesthetics

Answer 1

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

Question 2

General Anesthetic produce an unconscious state

Answer 2

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

Question 3

Depress the CNS

Answer 3

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

Question 4

Depress CV system

Answer 4

1. Decreased contractility
2. Peripheral vasodilation
3. Reduced organ perfusion

Question 5

Depress Respiratory system

Answer 5

1. Induced Hypoxemia

2. Cause retention of secretions (pneumonia)

Question 6

Why do we use general anesthesia?

Answer 6

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

Question 7

4 stages of general anesthesia

Answer 7

analgesia excitement
surgical anesthesia
medullary paralysis

Question 8

analgesia

Answer 8

somewhat conscious

Question 9

excitement

Answer 9

unconscious & amnesic, but agitated & restless

Question 10

surgical anesthesia

Answer 10

slow, deep breathing, muscle relaxation

Question 11

medullary paralysis

Answer 11

breathing stops, CV collapse…. need support for life

Question 12

Inhaled agents

Answer 12

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

Question 13

Types of inhaled agents

Answer 13

gases

volatile liquids

Question 14

gases

Answer 14

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

Question 15

volatile liquids

Answer 15

halothane
isoflurane
desflurane
sevoflurane (newest)

Question 16

Inhaled agent pharmacokinetics

Answer 16

• 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

Question 17

pharmacokinetics

Answer 17

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

Question 18

reversal of anesthesia

Answer 18

• 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

Question 19

General Perturbation Theory

Answer 19

• 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

Question 20

Specific Receptor Theory

Answer 20

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

Question 21

reduced neurotransmission

Answer 21

• may cause strengthened inhibition/ reduced excitation

- a greater effect on excitatory transmission than inhibitory

Question 22

inhaled agent side effects

Answer 22

• 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

Question 23

intravenous agents

Answer 23

used for induction of anesthesia

from stage 1 to 3 quickly

Question 24

IV agents used

Answer 24

thiopental 
midazolam
propofol
ketamine
etomidate

Question 25

sodium pentathol (thiopental)

Answer 25

• depress RAS
• ultra short acting Barb (30 sec hypnosis)
• last 5-10 mins (mostly for induction)

Question 26

side effects of
sodium pentathol (thiopental)

Answer 26

cv depression (prob. w/ heart disease patients)
respiratory depression (significant)
risk stage 2 if adequate dose

Question 27

Propofol

Answer 27

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

Question 28

side effects of propofol

Answer 28

similar to Pentothal

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

Question 29

Ketamine

Answer 29

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

Question 30

side effects of ketamine

Answer 30

• 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)

Question 31

Etomidate

Answer 31

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

Question 32

adjuvants

Answer 32

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