Gas Inhalents (EB)

Question 1

Which current inhalation agents are volatile liquids?

Answer 1

iso Des Sevo

Question 2

Which current inhalation agent is a gas?

Answer 2

nitrous oxide

Question 3

What anesthetic properties are influenced by halogenation?

Answer 3

anesthetic potency, arrhythmic properties, flammability, chemical stability

Question 4

Flammability of gases? NB?

Answer 4

gone for the potent agent. NB: N2O supports combustion

Question 5

Why is recovery from gases so quick? Which one is the slowest?

Answer 5

barely any metabolism of the gases

Halothane is the slowest

Question 6

Physical properties of an inhalant that determines the methods of administration? (4)

Answer 6

molecular weight - Boiling point - Liquid density (specific gravity) - *vapor pressure

Question 7

Physical properties of an inhalant that influences drug kinetics (2)?

Answer 7

solubility of gases like
Blood gas solubility
Oil gas solubility

Question 8

What is Dalton’s law?

Answer 8

each gas has it’s own partial pressure on a container’s walls
TP = sum of partial pressures

Question 9

What is saturated vapor pressure?

Answer 9

molecules of a volatile liquid in a closed container at fixed temperature evaporate

Question 10

What is vapor pressure?

Answer 10

pressure exerted by the gaseous phase in the container at equilibrium

Question 11

The higher the standard vapor pressure, what does it mean for volatility?

Answer 11

The more volatile the agent, the higher the conc of molecules in gaseous phase.

Question 12

Why is SVP important for anesthesia?

Answer 12

determines the concentration needed for anesthesia

Question 13

Purpose of a vaporizer

Answer 13

dilute inhalational agents to a safe concentration

Question 14

Modern vaporizers are (3)

Answer 14

Agent specific,
Concentration calibrated,
Temperature compensated

Question 15

What special circumstances are needed because desflurance has a BP of 23.5 C?

Answer 15

vaporizer that is connected to electricity to warm it

Question 16

Relation of the blood-gas partition coefficient and induction/recovery/change of anesthetic depth

Answer 16

inversly related

Question 17

Relation of the oil-gas partition coefficient and anesthetic potency

Answer 17

direct correlation

Question 18

Rate of concentration rise in blood influenced by (4)

Answer 18

Inhaled conc and FGF
Alveolar ventilation
Solubility in blood
Cardiac output

Question 19

Sequence of partial pressure gradient

Answer 19

Vaporizer
Breathing system
Alveoli
Blood Brain

Question 20

Primary objective of movement from anesthesia machine to the brain

Answer 20

Same partial pressures on either side of every tissue ‘interface’

Question 21

How can you accelerated ‘washout’ from tissues

Answer 21

high FGF, Empty reservoir bag

Question 22

Washout from different tissues occurs at _ rates

Answer 22

different

Question 23

Factors affecting recovery (5)

Answer 23

• Alveolar ventilation
• Solubility
• CO
• Anesthesia duration
• Metabolism

Question 24

What is minimum alveolar concentration (MAC)?

Answer 24

The minimal alveolar conc of an inhalant anesthetic at 1 atm that provides immobility in 50% of the subjects exposed to a supramaximal noxious stimulus.

Question 25

Relationship between MAC and potency?

Answer 25

inversely related

Question 26

List iso, sevo, des, halo, and N2O by lowest to highest MAC

Answer 26

Lowest - Halo – Iso - Sevo – Des - N2O – Highest

Question 27

When is anesthetic gas measured?

Answer 27

Inhaled conc, Exhaled conc

Question 28

What is the ET gas conc a reflection of?

Answer 28

agent's tension in the brain

Question 29

Factors that decrease MAC (8)

Answer 29

``` 1-sedatives/analgesics/injectable anesthetics 2- N2O 3- increasing age 4- hypothermia 5- pregnancy 6- severe hypoxemia 7- severe hypercapnia 8- concurrent illness ```

Question 30

What constitutes severe hypoxemia

Answer 30

PaO2 < 40 mm Hg

Question 31

What constitutes severe hypercapnia

Answer 31

PaCO2 > 90 mmHg

Question 32

Unique feature of N2O

Answer 32

only gaseously stored inhalant

Question 33

Why is N2O even still used today?

Answer 33

provides analgesia

Question 34

CV side effects of N2O

Answer 34

minimal

Question 35

Onset and recovery of N2O

Answer 35

rapid

Question 36

How is N2O usually given

Answer 36

combined with other inhalant anesthetic agent

Question 37

MAC of N2O in animals

Answer 37

about 200%

Question 38

Can you administer N2O with a vaporizer?

Answer 38

no

Question 39

Why can you not administer less than 1/3 O2 in mixture with N2O?

Answer 39

proportioning device on modern flowmeters

Question 40

What is the second gas effect? What gas has it?

Answer 40

N2O accelerates initial uptake of an anesthetic gas given concomitantly

Question 41

What surgeries are contraindicated with N2O? Why?

Answer 41

THINGS WITH GAS FILLED SPACES - Rumen - Stomach (GDV) - unfasted animals - closed pneumothorax - ocular surgery

Question 42

Why does N2O have a risk of hypoxemia? How is this combated?

Answer 42

N2O rapidly diffuses into alveoli after administration is stopped. Dilution of O2 in alveoli -> risk of hypoxemia. Provide O2 for 10 minutes after turning off N2O

Question 43

Advantages of N2O (3)

Answer 43

second gas effect MAC sparing Analgesia

Question 44

Disadvantages of N2O (5)

Answer 44

``` low potency Diffusion into gas-filled spaces Potential for hypoxia Drug abuse Environmental impact ```

Question 45

Why are your dials sticky after using halothane?

Answer 45

0.01% thymol preservative in the halothane -> dissoves rubber

Question 46

CV effects of halothane

Answer 46

Depressed myocardial contractility Reduces CO, SV, MAP (dose dependent) Arrhythmogenic

Question 47

Why is halothane arrhythmogenic

Answer 47

sensitizes myocardial conduction to catecholamines

Question 48

Potency of isoflurane? Why?

Answer 48

very potent | MAC 1.3%-1.6%

Question 49

Resp effects of isoflurane?

Answer 49

resp depressant

Question 50

CV effects of iso

Answer 50

decrease BP

Question 51

Is iso put in a preservative?

Answer 51

no

Question 52

Induction and recovery of iso

Answer 52

both rapid

Question 53

Mac of sevo

Answer 53

2.3-2.6%

Question 54

Is there a preservative in sevo?

Answer 54

no

Question 55

How is compound A formed?

Answer 55

sevo degradation

Question 56

When is compound A nephrotoxic?

Answer 56

in rats, At high concentration

Question 57

What does compound A react with? What system therefore can it not be used in?

Answer 57

interaction with CO2 absorbent. Cant really be used in a rebreathing system

Question 58

MAC of desflurane

Answer 58

7-10%

Question 59

What is malignant hyperthermia?

Answer 59

potentially life-threatening myopathy

Question 60

What triggers malignant hyperthermia?

Answer 60

all 4 current volatile inhalant agents ((and depolarizing neuromuscular blocking agents))

Question 61

Animals most like to least likely to get malignant hyperthermia?

Answer 61

pigs >> horses and dogs > cats

Question 62

CS of malignant hyperthermia

Answer 62

hyperthermia | Muscle fasciculation Tachycardia

Question 63

How can you recognize early malignant hyperthermia?

Answer 63

monitoring temp and CO2 for early recognition

Question 64

Tx of malignant hyperthermia

Answer 64

Discontinue trigger Cooling Dantrolene

Question 65

US regulatory agencies for anesthetic gas toxicity (3)

Answer 65

NIOSH OSHE FDA

Question 66

How does halothane kill you?

Answer 66

halothane hepatitis (hepatic necrosis and death)