Question

Which muscle relaxant increases intracranial pressure?

• A. Mivacurium
• B. Atracurium
• C. Suxamethonium
• D. Vecuronium

Hint:

Suxamethonium's fasciculations raise afferent traffic and cerebral blood flow before paralysis, unlike the non depolarising agents.

Answer 1

The Correct Option is C

Step 1: Split the options into their two families.
Mivacurium, atracurium, and vecuronium are all non depolarising muscle relaxants. Suxamethonium, also called succinylcholine, is the one depolarising agent in the list.

Step 2: Recall what suxamethonium does to muscle before it paralyses it.
Suxamethonium first opens the acetylcholine receptor and causes visible muscle fasciculations, small uncoordinated twitches, before flaccid paralysis sets in. This burst of muscle spindle activity sends a wave of extra afferent traffic up to the brain.

Step 3: Connect this to intracranial pressure.
The afferent barrage raises cerebral electrical activity and cerebral blood flow, which pushes up intracranial pressure for a short window after the drug is given. This is why suxamethonium is used with caution, and often with a pretreatment dose of a non depolarising agent, in patients who already have raised intracranial pressure such as head injury.

Step 4: Check the non depolarising agents.
Mivacurium, atracurium, and vecuronium block the receptor without first triggering fasciculations. There is no afferent barrage, so none of them raise intracranial pressure the way suxamethonium does.

Final Answer:
Only the depolarising agent in the list carries this risk.
\[ \boxed{\text{Suxamethonium}} \]