228. Neuromuscular Blockers

Question 1

What are neuromuscular blocking agents used for?

Answer 1

Facilitating tracheal intubation, relaxing abdominal muscles, maintaining immobility during surgery, facilitating mechanical ventilation

Neuromuscular blockers are critical in anesthesia and critical care settings.

Question 2

What are the two subcategories of neuromuscular blockers?

Answer 2

Depolarizing agents and nondepolarizing agents

Each category has distinct mechanisms of action.

Question 3

How do depolarizing agents like succinylcholine work?

Answer 3

They cause persistent depolarization of the motor end plate and paralysis due to resistance to degradation by acetylcholinesterase

This leads to a prolonged effect at the neuromuscular junction.

Question 4

What is the mechanism of action of nondepolarizing agents?

Answer 4

They act as competitive antagonists at nicotinic acetylcholine receptors, impairing depolarization

This prevents muscle contraction.

Question 5

At what age does the maturation of neuromuscular transmission likely occur?

Answer 5

2 months of age

The neuromuscular junction is not fully developed at birth.

Question 6

What effect does immaturity of the neuromuscular junction have on neonates?

Answer 6

Increased sensitivity to neuromuscular blockade, requiring lower plasma concentrations of blockers

This is due to physiological differences in drug clearance.

Question 7

What is the volume of distribution in infants and its significance?

Answer 7

Infants have a larger volume of distribution due to higher extracellular fluid percentage, requiring larger doses of neuromuscular blockers

This is crucial for effective dosing.

Question 8

What type of muscle fibers are more sensitive to neuromuscular blockade?

Answer 8

Type 1 muscle fibers

Preterm neonates have a limited percentage of these fibers in the diaphragm.

Question 9

What is the dosage and onset time for succinylcholine?

Answer 9

4 mg/kg IM produces intubating conditions within 4 minutes

Succinylcholine is favored for rapid airway management.

Question 10

What serious complications are associated with succinylcholine use?

Answer 10

Cardiac arrest, malignant hyperthermia, masseter muscle rigidity, profound vagal response leading to bradycardia

These risks necessitate careful monitoring.

Question 11

What are some commonly used nondepolarizing agents?

Answer 11

Rocuronium, vecuronium, cisatracurium, pancuronium, mivacurium

Each has different onset times and durations.

Question 12

What is the onset time and dose for rocuronium?

Answer 12

Fastest onset among nondepolarizing agents; intubating dose is 0.6 mg/kg

Produces conditions in approximately 0.8–1.3 minutes.

Question 13

What is vecuronium’s intubating dose and its effect on heart rate?

Answer 13

Intubating dose is 0.1 mg/kg with minimal increase in heart rate

Higher doses increase duration significantly.

Question 14

How does cisatracurium differ in metabolism?

Answer 14

Metabolism does not depend on hepatic or renal systems, safe in liver or kidney failure

This makes it a versatile option in high-risk patients.

Question 15

What is the primary excretion route for pancuronium?

Answer 15

Renally excreted

It can cause tachycardia due to norepinephrine uptake interference.

Question 16

What is a unique feature of mivacurium?

Answer 16

Rapidly cleared by plasma cholinesterase, allowing for spontaneous recovery

Associated with histamine release, causing flushing and hypotension.

Question 17

What is the role of acetylcholinesterase inhibitors in neuromuscular blockade?

Answer 17

They reverse nondepolarizing neuromuscular blockade, commonly using neostigmine

Doses of 0.07 mg/kg are standard.

Question 18

What is sugammadex and its role in anesthesia?

Answer 18

A selective binding agent that encapsulates neuromuscular blockers, rendering them ineffective

It is a safe alternative for reversing rocuronium and vecuronium in pediatrics.