Intravenous and inhalational agents: lithium and neuromuscular blockers: practice question

A Anaesthesia 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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Anaesthesia · Intravenous and inhalational agents: lithium and neuromuscular blockers

Sample item

A man on long-term lithium for bipolar disorder recovers more slowly than expected from rocuronium. What is the explanation?

ALithium reduces binding of anticholinesterases at the end plate onlyBLithium potentiates neuromuscular blockade, so block lasts longer and monitoring is neededCLithium inhibits hepatic metabolism of rocuroniumDLithium causes hyperkalaemia that augments non-depolarising block

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

The answer and the reasoning

B. Lithium potentiates neuromuscular blockade, so block lasts longer and monitoring is needed

Lithium prolongs the effect of both depolarising and non-depolarising relaxants, so doses are reduced and neuromuscular function is monitored. Lithium levels are also affected by dehydration and NSAIDs, and toxicity is checked perioperatively.

Option by option

A. Lithium reduces binding of anticholinesterases at the end plate only
Lithium does not specifically block anticholinesterase binding.
B. Lithium potentiates neuromuscular blockade, so block lasts longer and monitoring is needed (correct)
Correct. Lithium augments neuromuscular blockade.
C. Lithium inhibits hepatic metabolism of rocuronium
Rocuronium is not mainly metabolised in the liver, and lithium does not act that way.
D. Lithium causes hyperkalaemia that augments non-depolarising block
Hyperkalaemia would antagonise rather than augment non-depolarising block.

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 Anaesthesia question

What is the answer to this Anaesthesia question?

The best answer is B, Lithium potentiates neuromuscular blockade, so block lasts longer and monitoring is needed. Lithium prolongs the effect of both depolarising and non-depolarising relaxants, so doses are reduced and neuromuscular function is monitored.

Why is "Lithium reduces binding of anticholinesterases at the end plate only" not the answer?

Lithium does not specifically block anticholinesterase binding.

Why is "Lithium inhibits hepatic metabolism of rocuronium" not the answer?

Rocuronium is not mainly metabolised in the liver, and lithium does not act that way.

Why is "Lithium causes hyperkalaemia that augments non-depolarising block" not the answer?

Hyperkalaemia would antagonise rather than augment non-depolarising block.

What concept does this question test?

It tests Intravenous and inhalational agents: lithium and neuromuscular blockers in Anaesthesia. Lithium levels are also affected by dehydration and NSAIDs, and toxicity is checked perioperatively.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Intravenous and inhalational agents: lithium and neuromuscular blockers?

Make a table of each agent, its key advantage and its main side effect. Then use the flashcards and the other Anaesthesia 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.