anesthetic drugs (inhalants)

Question 1

what are the major, minor and not in use yet inhalant anethetics

Answer 1

major use

• isoflurane
• sevoflurane

minor use

• desflurane
• nitrous oxide

not in use yet

• argon

Question 2

partition coefficients - B/G and O/G

Answer 2

• isoflurane had higher B/G and O/G = waits longer to get induced and accumulates stronger and longer - need to flush out with O2 to wake naimal up)
• sevoflurane and desoflurane and N2O have lower B/G and O/G = induced quickly and washed out faster/animal wakes up faster)

Question 3

understand design of desoflurane vaporizers

Answer 3

watch zoom recording

Question 4

what are the CNS sites of action of inhalant anesthetics

Answer 4

spinal cord and brain stem

• inhibition of: sensory processing, nociceptive signaling, motor response to noxious stimulation

brain

• hypnosis & amnesia
• loss of consciousness
• analgesia

Question 5

what is MAC

Answer 5

• minimum alveolar concentration
• the anesthetic concentration preventing motor response to a supramaximal moxious stimulus in 50 % of subjects

Question 6

MAC dosing

Answer 6

• measure of potency
• given as vol. - % of Panes (mmHg)
• agent-specific
• species-specific
• correlates inversely with O/G part. coeff.

Question 7

what are factors that decrease MAC value

Answer 7

• increasing age
• pregnancy (endogenous opioid release)
• hypothermia
• hypotension (MAP < 40 mmHg)
• CNS depressant drugs/analgesics

Question 8

what are factors that increase MAC value

Answer 8

• hyperthermia
• hypernatremia

Question 9

respiratory system adverse effects

Answer 9

• central respiratory depression
• decrease Vt: iso> sevo > des
• bronchodilation

Question 10

adverse effects on CV system

Answer 10

• decrease MAP
• decrease systemic vascular resistance
• decrease myocardial contractility

Question 11

adverse effects on the liver

Answer 11

• decrease in liver blood flow
• decreases drug metabolism by 50-70%
• hepatotoxicity

Question 12

adverse effects on fetus

Answer 12

uteroplacental blood flow is decreased

Question 13

sevoflurane - formation of compound A

Answer 13

lower flow rates make more compound A

Question 14

what is balanced anethesia

Answer 14

concept using a combination of different agents and techniques to produce the four elements of anesthesia

• hypnosis and amnesia
• analgesia
• muscle relazation
• absence of somatic or autonomuc responses to noxious stimulation

Question 15

what does lowing inhalant anesthetic dose do

Answer 15

• palpebral reflexes less suppressed
• hemodynamic parameteres (esp. arterial blood pressures (ABP) often closer to physiological values

Question 16

where does most of the anesthetic accumuate

Answer 16

muscle

Question 17

how can the anesthetist influence onset and depth of anesthesia

Answer 17

• change of partial pressure for the anesthetic (PPanes) or its concentration (Concanes) in inspired gas mixture by: (dialing vaporizer up or down, changing fresh gas flow rate, selecting appropriate circuit system)

because:

• every change in PPanes or Concanes in the CNS follows changes of PPanes in alveolar gas mixture and arterial blood

Question 18

what are 3 factors affecting inspired gas concentration (Fi) or iPPanes

Answer 18

1. fresh gas flow rate
2. volume of breathing circuit (apparatus dead space)
3. absorption

Question 19

factors affecting alveolar concentration

Answer 19

• delivery via circuit
• pulmonary uptake: blood/gas solubility (B/G) coefficient & pulmonary blood flow (with modern volatile agents almost irrelevant)
• tissue uptake: tissue solubility of anesthetic agent, tissue blood flow, partial pressure difference between arterial blood and tissues

Question 20

factors affecting arterial concentration

Answer 20

depends on ventilation/perfusion (V/Q) mismatching