CNS drugs and antiepileptics: desflurane airway effects: practice question

A Pharmacology question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Pharmacology · CNS drugs and antiepileptics: desflurane airway effects

Sample item

An anaesthetist avoids inhalational induction with desflurane in a child scheduled for a day-case procedure. What is the principal reason?

AFormation of compound A with soda limeBIts pungency irritates the airway, causing cough and laryngospasmCVery slow onset from high blood solubilityDHepatotoxicity through trifluoroacetylated liver proteins

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

B. Its pungency irritates the airway, causing cough and laryngospasm

Desflurane has the lowest blood-gas solubility of the volatile agents, so onset and recovery are fast. It is pungent, though, and irritates the airway, causing breath-holding, coughing and laryngospasm at induction. It needs a heated pressurised vaporiser because its boiling point is near room temperature.

Option by option

A. Formation of compound A with soda lime
Compound A formation with soda lime is the concern with sevoflurane.
B. Its pungency irritates the airway, causing cough and laryngospasm (correct)
Correct. Pungency and airway irritation make it unsuitable for mask induction.
C. Very slow onset from high blood solubility
Its blood solubility is very low, giving fast onset, not slow onset.
D. Hepatotoxicity through trifluoroacetylated liver proteins
Hepatitis through trifluoroacetylated proteins is the concern with halothane.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

Questions about this Pharmacology question

What is the answer to this Pharmacology question?

The best answer is B, Its pungency irritates the airway, causing cough and laryngospasm. Desflurane has the lowest blood-gas solubility of the volatile agents, so onset and recovery are fast.

Why is "Formation of compound A with soda lime" not the answer?

Compound A formation with soda lime is the concern with sevoflurane.

Why is "Very slow onset from high blood solubility" not the answer?

Its blood solubility is very low, giving fast onset, not slow onset.

Why is "Hepatotoxicity through trifluoroacetylated liver proteins" not the answer?

Hepatitis through trifluoroacetylated proteins is the concern with halothane.

What concept does this question test?

It tests CNS drugs and antiepileptics: desflurane airway effects in Pharmacology. It is pungent, though, and irritates the airway, causing breath-holding, coughing and laryngospasm at induction. It needs a heated pressurised vaporiser because its boiling point is near room temperature.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study CNS drugs and antiepileptics: desflurane airway effects?

Learn drugs as classes, then the exception in each class that an examiner would pick. Then use the flashcards and the other Pharmacology questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.