Topic: Neuromuscular blockers 1. Fastest acting non depolarising blocker is Rocuronium 2. Longest acting neuromuscular blocker is Pancuronium 3. Vagal stimulation is caused by succinylcholine 4. Most potent skeletal muscle relaxant is Doxacurium 5. Shoest acting non depolarising neuromuscular blocker is Mivacurium
**Core Concept**
The question tests the knowledge of different types of neuromuscular blockers, their pharmacological properties, and clinical uses. Neuromuscular blockers are a class of drugs that can be either depolarizing or non-depolarizing, and they are used to facilitate tracheal intubation, provide muscle relaxation during surgery, and manage certain medical conditions.
**Why the Correct Answer is Right**
Option 5 states that Mivacurium is the shortest acting non-depolarizing neuromuscular blocker. This is correct because Mivacurium is a benzylisoquinolinium compound with a rapid onset of action and a short duration of action, typically lasting around 12-15 minutes. Its short duration of action is due to its rapid hydrolysis by plasma cholinesterase. Mivacurium is often used in clinical settings where a short duration of muscle relaxation is required, such as in pediatric anesthesia or in patients with renal or hepatic dysfunction.
**Why Each Wrong Option is Incorrect**
**Option A:** Rocuronium is a non-depolarizing neuromuscular blocker, but it is not the fastest acting. Rocuronium has a rapid onset of action, but it is slower than succinylcholine, a depolarizing neuromuscular blocker.
**Option B:** Pancuronium is a long-acting non-depolarizing neuromuscular blocker, but its duration of action is not the longest. Pancuronium has a duration of action of around 60-120 minutes, which is longer than some other non-depolarizing blockers, but not the longest.
**Option C:** Vagal stimulation is not a characteristic of succinylcholine. Succinylcholine can cause muscle fasciculations and an increase in intragastric pressure, but it is not typically associated with vagal stimulation.
**Option D:** Doxacurium is a potent non-depolarizing neuromuscular blocker, but it is not the most potent. Doxacurium has a high potency and a long duration of action, but it is not more potent than some other non-depolarizing blockers.
**Clinical Pearl / High-Yield Fact**
Mivacurium is a useful alternative to succinylcholine in patients with certain medical conditions, such as hyperkalemia or cardiac arrest, due to its shorter duration of action and reduced risk of hyperkalemia.
**Correct Answer:** E. Mivacurium is the shortest acting non-depolarizing neuromuscular blocker.