General Anesthetics

Question 1

components of anesthetic state

Answer 1

amnesia, immobility in response to noxious stimulation, attenuation of autonomic responses to noxious stimuli, analgesia, unconsciousness

Question 2

measurement of inhalational anesthetics

Answer 2

MAC units
minimum alveolar concentration= prevents movements in response to surgical stimulation in 50% of subjects (use about 1.3-1.5 MACs)

can be monitored continuously (end-tidal anesthetic concentration) and correspond with free concentration in blood

Question 3

modern anesthesiology relies on

Answer 3

combinations of iv and inhaled drugs to balance properties

Question 4

minor superficial surgery or invasive diagnostic procedures

Answer 4

general anesthesia not necessary
local anesthesia, analgesia or sedation
retention of patients ability to maintain airway, respond to verbal commands

Question 5

extensive surgical procedures

Answer 5

begin with preoperative benzodiazepines
induced with an intravenous agent (eg, thiopental or propofol)
maintained with a combination of inhaled (eg, volatile agents, nitrous oxide) and/or IV drugs (eg, propofol, opioid analgesics)

Question 6

How do GA enhance inhibitory activity

Answer 6

Chloride channels (volatile and IV)
Activation of two-pore domain K channels (volitile)

Question 7

How do GA inhibit excitatory activity

Answer 7

AMPA, NMDA (glutamate) - ketamine, nitrous oxide

Nicotinic and muscarinic receptors (Ach)

Question 8

Volatile anesthetics

Answer 8

Halothane, enflurane, isoflurane, desflurane, sevoflurane
Low vapor pressures, high boiling points
Liquids at room temperature (20°C)
Administered using vaporizers

Question 9

Gaseous anesthetics

Answer 9

Nitrous oxide
High vapor pressure, low boiling point
Gas at room temperature

Question 10

factors controlling uptake of inhaled anesthetics

Answer 10

inspired concentration and ventilation
Solubility
Alveolar-venous partial pressure difference

Question 11

alveolar venous partial pressure difference

Answer 11

Dependent mainly on uptake of the anesthetic by the tissues, including nonneural tissues

Influenced by tissue:blood partition coefficients, rates of blood flow to the tissues, and concentration gradients.

Question 12

4 stages of CNS depression

Answer 12

analgesia (some amnesia)
excitement (delirious, rapid respiration, hr and bp inc)
surgical anesthesia (slowing of respiration and hr)
medullary depression (require circulatory and respiratory support)

Question 13

barbiturates examples

Answer 13

thiopental, methohexital

largely replaced as induction agents by propofol

Question 14

barbiturates MOA

Answer 14

Combination of enhancement of inhibitory and inhibition of excitatory neurotransmission
Inhibitory transmission: activation of the GABAA receptor complex
Effects on excitatory transmission are less well understood

Question 15

barbs PK

Answer 15

Pharmacokinetics
Hepatic metabolism
Thiopental is metabolized more slowly, long elimination half-time
Recovery after single bolus is comparable for thiopental and methohexital - depends on redistribution to inactive tissue sites rather than on metabolism

Question 16

barbs effects

Answer 16

CNS - sedation to GA
no analgesia, may reduce pain threshold
CD - decrease BP d/t vasodilation
Respiratory depressants

Question 17

benzodiazepines examples

Answer 17

midazolam, lorazepam, diazepam

Question 18

desired effects benzos

Answer 18

Most desired effects are anxiolysis and anterograde amnesia

Question 19

action of benzos terminated by

Answer 19

selective antagonist, flumazenil

Question 20

pk benzos

Answer 20

Highly lipid-soluble, rapidly enter the CNS, rapid onset of action
Followed by redistribution to inactive tissue sites and termination of effect
Midazolam has the shortest context-sensitive half-time
Only benzodiazepine drugs suitable for continuous infusion

Question 21

benzos act through

Answer 21

GABA receptors

Question 22

etomidate desired effects

Answer 22

hypnotic but not analgesix

Question 23

etomidate mechanism

Answer 23

Likely acts through potentiation of GABAA-mediated chloride currents, like most other intravenous anesthetics.

Question 24

etomidate pk

Answer 24

Induction dose of etomidate produces rapid onset of anesthesia
Recovery depends on redistribution to inactive tissue sites
Larger doses, repeated boluses, or continuous infusions can safely be administered
Because (1) minimal effects on hemodynamics and (2) short context-sensitive half-time

Question 25

etomidate effects

Answer 25

cerebral vasoconstrictor
cv stability
some resp depression
adrenocortical suppression

Question 26

Hghly lipid-soluble phencyclidine (PCP) derivative producing significant analgesia

Answer 26

Ketamine

Question 27

kind of anesthesia ketamine does

Answer 27

“dissociative anesthesia,”

patient’s eyes remain open with a slow nystagmic gaze (cataleptic state)

Question 28

moa ketamine

Answer 28

inhibition of nmda receptor complex

Question 29

pharmacokinetics ketamine

Answer 29

High lipid solubility of ketamine ensures a rapid onset of its effect
Metabolism occurs primarily in the liver
Effect of a single bolus injection terminated by redistribution to inactive tissue sites

Question 30

ketamine effects

Answer 30

amnesia (not as complete as benzodiazepines)
cerebral vasodilator
unpleasant emergence reactions
transient but significant inc bp, hr, co
no resp depression, bronchodilation

Question 31

opioid analgesics distinct how

Answer 31

Recall not reliably prevented unless hypnotic agents such as benzodiazepines are also used

Postoperative analgesia and intraoperatively as part of a balanced anesthesia

Question 32

fentanyl is a

Answer 32

opioid analgesic

Question 33

___ + ____ = GA state

Answer 33

Large dose opioids + large dose benzodiazepines

Question 34

AE opioid analgesics

Answer 34

Hemodynamic stability - good for patients with compromised myocardial function
Respiration must be maintained artificially and may be depressed into the postoperative period
Can induce chest wall (and laryngeal) rigidity, acutely impairing mechanical ventilation
May speed up tolerance, complicate postoperative pain management

Question 35

how do inhaled anesthetics affect cardiovascular

Answer 35

Halothane, enflurane, isoflurane, desflurane, and sevoflurane all depress normal cardiac contractility (at some level)
Tend to decrease mean arterial pressure in direct proportion to alveolar concentration
Halothane and enflurane → myocardial depression (reduced CO) (little change in vascular resistance)
Isoflurane, desflurane, and sevoflurane produce greater vasodilation with minimal effect on CO (preferred for patients with impaired myocardial function)
Nitrous oxide also depressed myocardial function in a concentration-dependent manner (may be offset by activation of SNS → preservation of CO)