Pharmacology of Anesthesia MCQS PDF with answers and explanations

 

Chapter 1^st

Pharmacology of Anesthesia

 
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1.   What is the minimum oxygen concentration used in anesthetic mixture to maintain oxygenation?
A. 10%
B. 20%
C. 30%
D. 40%

2.   Pre-oxygenation before induction is done to?
A. Improve oxygen saturation
B. Eliminate CO₂
C. Denitrogenate
D. Increase dissolved fraction
E. All of these

3.   With which of the following inhalational agent it will be difficult to demonstrate/distinguish the stages of anesthesia?
A. Ether
B. Methoxyflurane
C. Isoflurane
D. Desflurane

4.   Inhalational agent with increased MAC will have _____ potency.
A. Increased
B. Decreased
C. No effect
D. Either decrease or increase

5.   Balanced anesthesia does not includes?
A. Amnesia
B. Analgesia
C. Muscle relaxation
D. Narcosis
E. None of the above

6.   Meyer–Overton rules relate to:

Anesthetic potency to lipid solubility
B. Anesthetic potency to blood gas solubility
C. Anesthetic induction to blood gas solubility
D. Anesthetic recovery to blood gas solubility

 

7.   Most potent inhalational anesthetic agent is?
A. Methoxyflurane
B. Halothane
C. Desflurane
D. Nitrous oxide

8.   Slowest induction and recovery is seen with?

A.    Halothane

B.    Isoflurane 

C.    Methoxyflurane

D.   Desflurane

9.    Which of the following inhalational agent is not metabolized by human body?
A. Halothane
B. Isoflurane
C. Nitrous oxide
D. Cyclopropane

 

10.       All of the following agents inhibit ciliary activity except?
A. Halothane
B. Isoflurane
C. Ether
D. Desflurane

11.       After induction the first reflex to go is?

A.    Eyelash

B.    Corneal

C.    Laryngeal

D.   Carinal

12.       Which inhalational agent causes diffusion hypoxia and second gas effect?

A.    Isoflurane

B.    Enflurane

C.    Sevoflurane

D.   Nitrous oxide

 

13. Which inhalational agent causes diffusion hypoxia and second gas effect?
A. Isoflurane
B. Enflurane
C. Sevoflurane
D. Nitrous oxide

 

14. Which of the following agents does not cause direct hepatotoxicity?
A. Isoflurane
B. Halothane
C. Methoxyflurane
D. Chloroform

 

15. Agent which does not produce fluorides on metabolism?
A. Isoflurane
B. Halothane
C. Methoxyflurane
D. Desflurane

 

16. Under normal conditions, all of the following agents are fluorinated except?
A. Isoflurane
B. Halothane
C. Methoxyflurane
D. Sevoflurane

 

17. Highest fluoride production is done by?
A. Halothane
B. Isoflurane
C. Methoxyflurane
D. Desflurane

 

18. All of the following agents sensitize myocardium to adrenaline except?
A. Halothane
B. Chloroform
C. Ether
D. Trielene

 

19. Prolonged exposure to nitrous oxide may cause which condition?
A. Megaloblastic anemia
B. Hepatitis
C. Renal failure
D. Coronary steal

 

20. Which of the following determines inspired gas concentration (Fi)?
A. Vapor pressure
B. Fresh gas flow rate, breathing-circuit volume, and circuit absorption
C. Alveolar ventilation and cardiac output
D. Blood/gas solubility

 

21. Which of the following is a major determinant of recovery speed?
A. Redistribution and pulmonary elimination
B. Hepatic metabolism
C. Renal clearance
D. Plasma protein binding

 

22. Which of the following factors speeds both induction and recovery?
A. Increased circuit absorption
B. High solubility
C. Decreased solubility
D. Rebreathing

23. What are the three main factors that affect anesthetic uptake from the alveoli?
A. Solubility in blood, alveolar blood flow, and alveolar–venous partial pressure difference
B. Inspired concentration, ventilation rate, and MAC
C. Blood/gas partition, body temperature, and hepatic metabolism
D. Circuit volume, fresh gas flow, and rebreathing

 

24. Which factor does not increase the rate of induction?
A. High fresh gas flow
B. Low circuit absorption
C. High blood solubility
D. Low anesthetic circuit volume

 

25. Which statement best describes the relationship between anesthetic uptake and induction speed?
A. Greater uptake → faster induction
B. Greater uptake → slower induction
C. Uptake has no effect
D. Uptake only affects recovery

 

26. A high oil:gas partition coefficient indicates:
A. Low potency (high MAC)
B. High potency (low MAC)
C. Rapid onset and offset
D. Poor lipid solubility

 

27. Which of the following will decreases MAC (increases sensitivity to volatile anesthetic)?

A.    Acute alcohol intoxication

B.    Hyperthermia

C.    Chronic opioid use

D.   Elderly age

 

28. Which is true regarding the relationship between cardiac output and induction speed for a highly blood-soluble agent?
A. Increased cardiac output speeds induction
B. Increased cardiac output slows induction
C. Cardiac output has no effect
D. Only decreased cardiac output slows induction

29. Compound A formation (with potential nephrotoxicity in animals) is a concern with which agent when low fresh gas flows and certain CO₂ absorbents are used?
A. Desflurane
B. Sevoflurane
C. Isoflurane
D. Nitrous oxide

30. An elderly patient requires less volatile anesthetic than a young adult because:
A. Elderly have higher blood:gas solubility
B. MAC decreases with increasing age
C. Elderly have increased metabolic clearance of inhaled agents
D. Elderly have smaller FRC always

 

31. Which volatile agent is most commonly associated historically with arrhythmias when used with epinephrine-containing local anesthetics?
A. Desflurane
B. Sevoflurane
C. Isoflurane
D. Halothane

 

32. Which of the following can decrease the MAC in severe case?
A. Hypoxia
B. Hypernatremia
C. Hyperthermia
D. Female gender

 

33. A high inspired concentration of a volatile agent is used to speed induction — this effect is called?
A. Diffusion hypoxia
B. Second gas effect
C. Concentration effect
D. MAC-awakening effect

 

34. Liver metabolism of volatile anesthetics can lead to production of toxic metabolites; which pair is correct?
A. Desflurane → trifluoroacetic acid (minimal)
B. Nitrous oxide → trifluoroacetic acid
C. Sevoflurane → halothane metabolites
D. Isoflurane → compound A

 

35. For a very soluble anesthetic agent, which strategy will accelerate induction?
A. Increase cardiac output
B. Decrease alveolar ventilation
C. Increase inspired concentration
D. Increase FRC

 

36. Chronic exposure to nitrous oxide can cause deficiency of which vitamin/cofactor by oxidizing it?
A. Vitamin D
B. Vitamin B12 (cobalamin)
C. Vitamin K
D. Folate only

 

37. Which of the following factors will decrease the minimum alveolar concentration (MAC) of a volatile anesthetic?
A. Hyperthermia
B. Chronic alcoholism
C. Pregnancy
D. Increased catecholamine levels

 

38. Which volatile anesthetic is most commonly associated with the formation of carbon monoxide when used with desiccated CO₂ absorbent?
A. Sevoflurane
B. Desflurane
C. Halothane
D. Nitrous oxide

 

39. During a long case, the anesthesiologist reduces the fresh gas flow to 0.5 L/min while using sevoflurane. What risk increases?
A. Formation of Compound A
B. Carbon monoxide toxicity
C. Hypoxia
D. Increased MAC

 

40. A patient develops signs of malignant hyperthermia after exposure to volatile anesthetics. Which physiologic change occurs first?
A. Sudden drop in end-tidal CO₂
B. Muscle rigidity and increased CO₂ production
C. Hypokalemia
D. Metabolic alkalosis\

41. A patient on cardiopulmonary bypass has low cardiac output — how will induction with a poorly soluble volatile be affected?
A. Induction will be significantly slower.
B. Induction will be faster because low CO reduces uptake.
C. Cardiac output doesn't matter for poorly soluble gases.
D. Induction speed will match that of highly soluble agents.

 

42. A patient with high FRC (e.g., COPD) undergoes induction with isoflurane. What is the expected effect on speed of induction?
A. Induction is slower.
B. Induction is faster.
C. No change.
D. Depends on inspired oxygen.

 

43. Which inhalational agent causes the greatest reduction in systemic vascular resistance (SVR)?
A. Isoflurane.
B. Sevoflurane.
C. Halothane.
D. Nitrous oxide.

 

44. Why is nitrous oxide not used as the sole anesthetic for major surgery?
A. It is too potent and depresses respiration completely.
B. It has high MAC and low potency.
C. It causes bradycardia.
D. It increases hepatic metabolism.

 

45. Which anesthetic gas can lead to bone marrow suppression after chronic exposure?
A. Nitrous oxide.
B. Desflurane.
C. Sevoflurane.
D. Isoflurane.

46. A 40-year-old man with severe COPD requires general anesthesia. Which volatile agent provides bronchodilation with minimal airway irritation?
A. Desflurane.
B. Isoflurane.
C. Sevoflurane.
D. Halothane.

 

47. A 40-year-old woman undergoing breast surgery is maintained on desflurane and nitrous oxide. How does nitrous oxide affect the MAC of desflurane?
A. Increases MAC.
B. Decreases MAC.
C. No effect.
D. Causes unpredictable response.

 

48. A 75-year-old man requires general anesthesia. How should the volatile anesthetic dose be adjusted?
A. MAC increased.
B. MAC decreased.
C. No change.
D. Depends on inspired oxygen.

 

49. Which volatile anesthetic causes the most increase in heart rate at high concentrations?
A. Halothane.
B. Isoflurane.
C. Sevoflurane.
D. Desflurane.

 

50. A patient with high alveolar ventilation receives isoflurane for induction. How will this affect onset?
A. Induction will be faster.
B. Induction will be slower.
C. No change.
D. Depends on MAC.

 

 

 

 

 

 

 

Answers and Explanations

Explanations

1.    Minimum concentration of oxygen should be 33% and now this is the safety mechanism available in newer machines that they do not deliver oxygen less than 33% ~ 30%

2.    Denitrogenations means removal of nitrogen from lungs is the aim of pre oxygenation. The oxygen reserve which can be utilized by the body is in the form of functional residual capacity (FRC) in lung which contains only 500ml of oxygen which is 21% of normal FRC making about 2.5 liters oxygen which will last for 2 minutes only (oxygen consumption is 250ml/min). with pre oxygenation the 95% of nitrogen can be removed in 3 minutes making the almost whole FRC to be filled with oxygen which can last for 8 to 10 minutes.

 

3.    To demonstrate the stages of anesthesia the induction of the agent should be very slow so that one can find the stages but as inhalational agents using nowadays are having faster induction and recovery so it cant be used for this purpose. Now as blood gas solubility of desflurane is lowest than among all other agents mentioned in MCQ due to which its induction and recovery is very fast that’s why it cant be used comparably to others. For reference visit MCQ No.3 for chart

 

4.     As we know that potency is inversely proportional to the MAC so the agent with highest or increased MAC will have lower potency and vice versa. Also potency is directly proportional to the lipid or oil gas solubility coefficient. For reference check MCQ NO 3 and 4 for chart

 

5.    The anesthesia nowadays should be balanced anesthesia composing of (Amnesia, analgesia, narcosis (unconsciousness) and muscle relaxation.

 

6.    (A) Meyer Overton rules states that anesthesia potency is directly proportional to the lipid solubility

 

7.    (A) As we know that (discussed previously) that potency is inversely proportional to the MAC of the inhalational agent so in these options methoxyflurane has the lowest MAC which is 0.16% making it the most potent inhalational agent.

 

Potency order of inhalational agents in decreasing order is as under:

Methoxyflurane>Halothane>Isoflurane>Sevoflurane>Desflurane> Nitrous oxide.

 

This order shows the methoxyflurane is most potent while N2o is least potent MAC (104%)

 

8.    (C) Blood gas solubility is inversely proportional to the speed of induction and recovery, so an agent with increased BGS will have slow induction and so recovery. As methoxyflurane has highest BGS (15) so its having slowest induction and recovery.

Decreasing order of the induction and recovery is as under:

Xenon>Desflurane>N2o>Sevoflurane>IsoflUrane>Halothane>Methoxyflurane

 

9.    (C) Nitrous oxide does not undergo any metabolism in human body.

10.           (C) Ether is the only inhalational agent which preserves the ciliary activity.

11.           (A) First reflex to go after induction is Eyelash reflex which goes in stage 2 while the last reflex to go is the carinal which goes in stage 3 & plane 4. These reflexes come in reverse order in recovery.

12.           (D)
Diffusion hypoxia:
At the end of the surgery when the N2o delivery from the machine is stopped the gradient between alveoli and blood is reversed and the nitrous oxides gushes into the alveoli replacing the oxygen form there creating hypoxia called as diffusion hypoxia.
Second gas effect:

Nitrous oxide is given in higher concentration (66%) uptake of nitrous oxide by blood will create a gradient in drawing more nitrous oxide from machine thus increasing the alveolar concentration more than expected. This Is called as concentration effect. If the other potent agent like halothane is given along with nitrous oxide by the same mechanism it also increases the concentration of halothane this is called as second gas effect.

 

13.           (A) Direct hepato-toxicity is causes by halothane, chloroform and methoxyflurane

 

14.           (C) Maximum fluoride is produced by methoxyflurane (50-80um) which is above renal threshold (50um). After methoxyflurane, fluoride production in decreasing order is by sevoflurane (30-50um), enflurane (20-25um). Isoflurane (4-8um) and halothane which can produce fluoride under anaerobic conditions. Desflurane does not produce fluorides even under anaerobic conditions.

 

15.           (B) Halothane does not produce fluorides under normal conditions but does produce under anaerobic condition, see explanation of MCQ NO. 14 for more.

 

16.           (C) Maximum fluoride is produced by methoxyflurane (50-80um) which is above renal threshold (50um). After methoxyflurane, fluoride production in decreasing order is by sevoflurane (30-50um), enflurane (20-25um). Isoflurane (4-8um) and halothane which can produce fluoride under anaerobic conditions. Desflurane does not produce fluorides even under anaerobic conditions.

17.           (c) Agents which sensitizes mycoradium to adrenaline are halothane, chloroform and trielene.

18.           (A) Prolonged exposure to nitrous oxide (N2O) causes megaloblastic anemia by oxidizing and inactivating vitamin B12, which is crucial for DNA synthesis. This inactivation of vitamin B12 blocks the enzyme methionine synthase, disrupting the formation of new DNA and leading to the production of abnormally large, immature red blood cells (megaloblasts)

19.           (B) The inspired gas concentration (Fi) that reaches the patient isn’t always the same as the vaporizer setting. It depends on how fast fresh gas is flowing into the circuit, how big the circuit is, and whether the tubing absorbs some anesthetic. Higher gas flow, smaller circuits, and less absorption mean Fi will closely match the vaporizer setting.

20.           (A) Waking up from anesthesia happens mainly when the anesthetic leaves the brain and goes back into the blood (redistribution), and then it’s exhaled through the lungs. This is why breathing faster after surgery helps patients wake up more quickly.

21.           (c) If an anesthetic doesn’t dissolve much in blood (low solubility), the blood saturates quickly and the brain reaches anesthetic levels faster — so both induction and recovery are quick. Highly soluble agents, on the other hand, take longer to “wash in” and “wash out.”

22.           (A) These three are the key determinants of how much anesthetic agent leaves the lungs

23.           (C) The patient wakes up (emergence) mainly because the anesthetic moves out of the brain and is exhaled through the lungs. Drugs that are less soluble in blood leave the body faster, so recovery is quicker.

24.           (c) Highly soluble anesthetics take longer to build up in the lungs because they keep dissolving into the blood. This slows down induction. In contrast, low-solubility gases saturate fast and make the patient fall asleep quickly.

25.           (B) The speed of induction with inhalational anesthetics depends on how quickly the alveolar concentration (FA) rises toward the inspired concentration (FI) — expressed as FA/FI.

·       Induction is faster when FA/FI rises quickly (alveolar concentration rapidly approaches inspired concentration).

·       Induction is slower when FA/FI rises slowly.

Role of Uptake
When an anesthetic gas is taken up (absorbed) more by the blood, less remains in the alveoli.

·       This means alveolar concentration rises more slowly,

·       So FA/FI increases more slowly,

·       And thus induction is slower.

·       Therefore: Greater blood uptake → slower rise of FA → slower induction.

26.           B. High potency (low MAC)
Explanation: Oil:gas solubility correlates with potency — agents with higher oil solubility are more potent and have lower MACs

27.           D. Elderly age
Explanation: MAC decreases with age (elderly require lower MAC). Acute alcohol actually may increase MAC; chronic opioid use does not change MAC for volatiles in the same way (it reduces MAC requirement for inhaled agents in practice via additive effects of opioids but the classic teaching emphasizes age and other factors).

28.           B. Increased cardiac output slows induction
Explanation: For soluble agents, higher CO carries more anesthetic away into blood and tissues, slowing alveolar concentration rise and delaying induction.

29.           B. Sevoflurane
Explanation: Sevoflurane can degrade in CO₂ absorbents to form compound A; low-flow systems raised concerns. Clinical significance in humans is debated but caution with very low flows exists.

30.           B. MAC decreases with increasing age
Explanation: MAC declines with age — older patients need lower alveolar concentrations to achieve anesthesia.

31.           D. Halothane
Explanation: Halothane sensitizes the myocardium to catecholamines and can predispose to arrhythmias.

32.           (A) Hypoxia
Explanation: when the partial pressure of oxygen (PO2) becomes less than 40mmhg (severe cases) then mac will be decreased.same is the cases with hypercarbia if its severe (>95mmhg) then mac will be decreased.

33.           C. Concentration effect
Explanation: The concentration effect means a high inspired concentration accelerates the rise of alveolar concentration because a larger partial pressure gradient exists initially.

34.           A. Desflurane → trifluoroacetic acid (minimal)
Explanation: Desflurane undergoes minimal metabolism producing small amounts of inorganic fluoride and trifluoroacetic compounds; halothane metabolism produced more reactive metabolites linked to hepatitis.

35.           C. Increase inspired concentration
Explanation: The concentration effect helps — a higher inspired concentration provides a larger gradient, partially offsetting slow uptake of soluble agents. Increasing CO or FRC slows induction.

36.            B. Vitamin B12 (cobalamin)
Explanation: N₂O oxidizes and inactivates cobalamin (vitamin B12), risking megaloblastic changes and neurologic injury with prolonged exposure.

37.           C. Pregnancy
Explanation: Pregnancy reduces MAC by about 25–30% because of elevated progesterone levels and increased endorphin activity, both of which enhance central nervous system sensitivity to anesthetics.

38.           B. Desflurane
Explanation: Desflurane reacts with dry CO₂ absorbents (especially containing strong bases) to produce carbon monoxide. Fresh absorbents and adequate humidity prevent this issue.

39.           A. Formation of Compound A
Explanation: Sevoflurane can degrade in certain CO₂ absorbents during low-flow anesthesia, forming Compound A, a potentially nephrotoxic compound in animals. Clinicians usually maintain at least moderate flow rates to minimize its formation.

40.           B. Muscle rigidity and increased CO₂ production
Explanation: The earliest indicator of malignant hyperthermia is an unexpected, rapid rise in end-tidal CO₂ due to uncontrolled muscle metabolism. Generalized rigidity, tachycardia, and hyperthermia follow soon after.

41.           Answer: B. Induction will be faster because low CO reduces uptake.
Explanation: Low cardiac output means less blood flow to take anesthetic away from the lungs, so less uptake occurs and alveolar concentration rises faster. Poorly soluble agents are already less affected by blood uptake, but low CO still tends to speed induction compared with high CO.

42.           A. Induction is slower
Explanation: A large functional residual capacity acts as a reservoir that dilutes inspired anesthetic, delaying the rise of alveolar concentration and slowing induction.

43.           B. Isoflurane
Explanation: Isoflurane causes marked arteriolar vasodilation and a dose-dependent fall in SVR. Blood pressure drops mainly from reduced afterload rather than myocardial depression, preserving cardiac output.

44.           B. It has high MAC and low potency
Explanation: Nitrous oxide has a MAC greater than 100%, meaning even at 100% concentration it cannot produce surgical anesthesia safely. It is usually combined with other volatile or intravenous agents.

45.           A. Nitrous oxide
Explanation: Chronic nitrous oxide exposure inactivates vitamin B12 by oxidizing its cobalt atom, leading to megaloblastic anemia and bone marrow suppression in long-term or occupational exposure.

46.           C. Sevoflurane
Explanation: Sevoflurane is non-pungent and produces smooth bronchodilation without provoking coughing or laryngospasm, making it the best choice for patients with reactive or obstructed airways such as COPD.

47.           B. Decreases MAC
Explanation: Nitrous oxide has additive anesthetic effects with volatiles, reducing the required alveolar concentration of desflurane to achieve anesthesia. This is known as the MAC-sparing effect.

48.           B. MAC decreased
Explanation: Aging reduces central nervous system responsiveness to anesthetics. Therefore, elderly patients require approximately 20–30% lower MAC compared to younger adults.

49.           D. Desflurane
Explanation: Desflurane can cause transient tachycardia and hypertension due to sympathetic activation, especially with sudden increases in concentration.

50.           A. Induction will be faster
Explanation: Increasing alveolar ventilation increases the amount of anesthetic reaching the alveoli per minute, which accelerates the rise in FA/FI and speeds induction. This effect is most notable with highly soluble agents

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