Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Anaesthesiology > Inhalation Agents > Flashcards

Inhalation Agents Flashcards

(65 cards)

Start Studying
1
Q

Which inhalation agents can be used for induction (2)

A

Halothane and sevoflurane (preferred)
Because not irritating to airways, smell pleasant

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Why would inhalation induction be used? (4)

A

• Children without iv access
• difficult iv access
• fear of needles
• difficult airway (spontaneous breathing maintained)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Classify the 2 groups of inhalation agents and their examples (11)

A

• Gases: nitrous oxide (technically a vapour below room temperature), xenon
• vapours:
-halogenated hydrocarbons (halothane),
-ethers ( diethylether, isoflurane, sevoflurane, desflurane)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What determines brain concentration of inhalation agents?

A

Partial pressure of agent in alveolus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What influences the rate of delivery of inhalation agents to the alveoli? (3)

A
  1. Alveolar ventilation (increased = faster onset)
  2. Functional residual capacity (smaller = faster)
  3. Inspiratory concentration of gas (higher-faster)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What influences the rate of removal of inhalation agents from the alveoli? (4)

A
  1. Partial pressure difference (alveolar pressure > blood = faster)
  2. Solubility of agent ( low BGPC -faster )
  3. Cardiac output
  4. Metabolism of agent
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the BGPC halothane

A

2,43
Highest- most soluble, slower action, slower recovery

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the BGPC isoflurane

A

1,4
Second most soluble and second slowest

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the BGPC sevoflurane

A

0,64.

Middle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the BGPC N20

A

0,47
Second least soluble and second fastest

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is the BGPC desflurane

A

0,42 - least soluble and fastest onset

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Define MAC

A

The minimum alveolar concentration necessary or required to prevent movement on surgical incision of the skin in 50% of patients

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

In lay terms, what is MAC?

A

Potency (fat solubility)
Lower = better

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is the MAC of halothane

A

0,77 (most potent )

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the MAC of isoflurane

A

1,15
Second most potent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the MAC of sevoflurane

A

2,05
Middle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the MAC of desflurane

A

6.
Second least potent

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the MAC of N20

A

105 (least potent)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Which patients may need higher MAC (7)?

A

HD CHIP

• Alcoholism chronic
• hyperthyroid
• hyperthermia
• infants and puberty
• Drug dependency
• narcotic misuse
• increased cardiac output

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Which patients may need lower MAC (10)?

A

How’s His ALPHA HEAD

• Hypothermia
•Hypothyroid
• elderly
• pregnancy
• hypoxemia
• anaemia
• hypotension, low cardiac output
• drugs: analgesics, sedatives, opioids, antihypertensives, barbiturates
• acutely intoxicated with alcohol
• low cardiac output
Acidosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

Name the CNS effects of inhalation agents (4)

A

• Decrease CMRO2
• cerebral vasodilation! - increased cerebral blood flow (unlike iv) - limited use in increased ICP (usually only if go over 1 mac with the esters. But halothane very bad vasodilation, contraindicated tbi)
• decrease set point of thermoregulation (post-op shivering)
• stimulate chemo-emetic trigger zone - nausea and vomiting!

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

Name the CVS effects of inhalation agents with specific example (4)

A

• mostly halothane = Direct cardiovascular depressant (CCB): decrease inotropy, chronotropy, dromotropy, lusitropy, afterload, preload. Slows conduction, sensitise to catecholamines (don’t use halothane with adrenaline!), directly decrease contractility. This leads to hypotension and dysrhythmias
• hypotension ethers due to decrease SVR and vasodilation

• Coronary vasodilation
• dysrhythmogenic - bradycardia, SVT ,Re-entry phenomena esp halothane, not newer agents like isoflurane..
. Sensitise myocardium for catecholamines (especially halothane)
• isoflurane: mild tachycardia,

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Name the respiratory effects of inhalation agents (4)

A

• Upper air way irritation (stinky) except halothane and sevoflurane; (therefore can not use ISO or des for induction)
• bronchodilation
• decrease ciliary function
• hypo-ventilation (depress muscle function) (not apnea)
• decreased response to hypercarbia and hypoxia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What colour is halothane?

A

Red

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What colour is isoflurane
Purple
26
What colour is sevoflurane
Yellow
27
What is different and notable of sevoflurane? (2)
• Emergence delirium • breakdown in desicated sodalime into compound A and changed by B lyase enzyme into nephrotoxic substance - not used if decreased renal function Cardiotoxic - decrease SVR and contractility, thus decreasing after load and CO.
28
What colour is desflurane?
Blue
29
What is different and notable of desflurane? (7)
Airway irritation- careful in asthma /smokers Very rapid recovery - ideal for obese and OSA. Useful in liver/renal failure (less than 1%. metabolised) High vapour pressure so need electronic vaporizer Lowest bgpc Produce Carbon monoxide in desiccated sodalime so risk co poisoning after weekend for eg Sympathetic stimulation on increase of concentration- tachycardia few minutes
30
Why is n20 sometimes used in combination with other volatile agents? (2)
• Increases potency (it has lowest) • faster onset of action (second fastest- bgpc 0,47 ) - second gas effect (need to give additional O2 for 20 min after N2O stopped bc cause diffusion hypoxia)
31
Name 7 side effects of nitrous oxide
1. Nausea and vomiting! 2. Bone marrow depression (prolonged exposure) 3. Diffuses into gas filled spaces and increases the volume eg lung bullae, pneumothorax, distended bowel loops, gas used in eye or ear surgery, et tube cuff inflation (pressure necrosis)... 4. cardiac suppression. If underlying CV disease 5. Teratogenic first trimester!- block methionine synthase enzyme. 6 Diffusion hypoxia (give oxygen for 20 min after n20 stopped) 7. Increase pulmonary vascular resistance: pulmonary vasoconstriction, rv failure with PHT
32
Which opioid has the highest potency?
Sufentanil (then remifentanil )
33
Which opioid has the lowest potency?
Morphine (then alfentanil)
34
What colour is enflurane vaporizer?
Orange
35
Name 4 factors that influence the rate of uptake in blood of inhalation agents.
• Solubility in blood (BGPC ) • cardiac output (tachycardia slow rate of rise of alveolar concentration) • concentration administered (fi) • alveolar ventilation (FA) (hyperventilation slow rate of rise of alveolar conc)
36
How does critical temperature influence phase change?
• A substance in gaseous phase below critical temperature of that substance can be forced into liquid phase by increasing pressure . But if above critical temperature, no amount of pressure increase will force a phase change and it will remain a gas.
37
Define vapour
Gaseous phase below critical temperature
38
Define gas
Gaseous phase above critical temperature
39
How is quantity of a gas measured?
By pressure gauge
40
How is quantity of a vapour measured?
By weight
41
Define vapour pressure
Partial pressure of gas particles that have escaped from a liquid by evaporation in a closed rigid container
42
What is boiling point?
When vapour pressure = barometric pressure
43
Barometric pressure in Gauteng?
650 mm Hg
44
Why does desflurane need special electronic vaporiser to be administered
Vapour pressure desflurane= 681 mm Hg Barometric pressure Gauteng =650 Therefore boils at room temperature
45
What is bgpc?
Blood gas partition coefficient Solubility of vapour in blood Higher = more soluble, slower action, slower recovery Low BGPC is better (faster)
46
Moa inhalation agents?
All GABA agonists Except n20: NMDA antagonist. Very good analgesic.
47
Where is halothane metabolised and what is complication of this?
Liver 20% Halothane hepatitis: immunologic reaction, toxic reductive metabolites, ischaemia High mortality
48
Name 6 predisposing factors to halothane hepatitis
• Female • middle age • obesity • multiple administrations • enzyme induction drug use • decreased glutathione (fasting)
49
Which agent has highest bgpc?
Halothane (2,3)
50
Which inhalation agent is best for neuro anaesthesia and why (4)
Isoflurane • maintain auto-regulation up to 1 MAC • non-epileptogenic • decrease CSF production and increase absorption therefore least increase in cerebral blood flow and ICP of all inhalation agents Also sevoflurane
51
Inhalation drug of choice liver disease patients? (2)
Desflurane best then Isoflurane ( added benefit of increasing arterial blood flow to liver) Only 0.2% metabolised by liver and maintains hepatic arterial blood supply
52
Which agent has lowest bgpc?
Desflurane Fastest onset and offset 0,45
53
Inhalation drug of choice for short cases?
Desflurane Lowest bgpc
54
How calculate MAC pt?
End tidal volume of agent ÷ MAC of agent
55
Which inhalational agent contraindicated in epilepsy?
Enflurane
56
Which inhalational agent can cause coronary steal?
Halothane
57
Name 4 factors that increase rate of induction of inhalation agents
• High inspiratory concentration . Low blood gas solubility coefficient bGpC • increased ventilation • low cardiac output
58
Define Henry's law
Concentration of gas directly proportional to partial pressure of the gas
59
Define Graham's law
Rate of diffusion of gas inversely proportional to molecular weight of the gas
60
Define Ostwald's solubility coefficient
Uptake of gas is proportional to the solubility of the gas
61
Name 2 major disadvantages of halothane
• Patients take very long to wake up (slow onset , offset and washout because highest bgpc therefore highest solubility) • high incidence dysrhythmias (ventricular extrasystoles)
62
Name 3 advantages nitrous oxide
• Great analgesic • good to use with induction due to second gas effect • good sedative
63
Describe the second gas effect of nitrous oxide
• Low bgpc 0,47 therefore less soluble • diffuses rapidly into blood • reduced alveolar volume • increased concentration of volatile agent
64
Name 4 anatomical differences in the neurological system in paeds
• Poorly developed blood brain barrier (increased sensitivity to drugs that cross bbb) • preterm- cerebral vessels thin walled and fragile . Spinal cord: end l2-L3 premature, l3 newborns • lack lumbar lordosis
65
Name 6 physiological differences in the neurological system in paeds
• Immature myelinisation of nerves • higher blood supply to spinal cord • total CSF volume higher • developing brain • separation anxiety • communication • prone to intraventricular haemorrhages

Anaesthesiology (24 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions