Neuromuscular Blocking Drugs

Question 1

What is the definition of NMBDs?

Answer 1

Interrupts transmission of nerve impulses at the neuromuscular junction

Question 2

What is the result of using NMBDs?

Answer 2

Complete paralysis of striated muscles while consciousness is retained, there is no analgesia, and spontaneous respiration ceases

Question 3

What is the major indication for use of NMBDs?

Answer 3

Aid for intraocular or corneal surgeries; most common indication in vet med

Question 4

What are minimum requirements when using NMBDs?

Answer 4

Use mechanical ventilation; monitor CV, respiratory systems, oxygenation, and neuromuscular function

Question 5

When using NMBDs, what are the only possible responses of the patient to noxious stimuli?

Answer 5

Tachycardia and high blood pressure

Question 6

What is the MOA of NMBDs (depolarizing vs non-depolarizing)?

Answer 6

Depolarizing: act as an agonist on the nicotinic ACh receptors, causing muscle membrane depolarization
Non-depolarizing: act as a competitive antagonist on the nicotinic ACh receptors, stabilizing muscle membranes

Question 7

What is the proper order in which muscle relaxation occurs with NMBDs?

Answer 7

Ocular muscles > all other muscles > diaphragm

Question 8

What type of drugs can potentiate NMBD effect?

Answer 8

Inhalation anesthetics; aminoglycoside antibiotics; local anesthetics; cardiac anti-arrhythmic drugs; diuretics; Mg

Question 9

What other factors can influence the depth of NMBD effect?

Answer 9

Hypothermia; electrolyte abnormalities; acid-base disorders; age; thermal burn

Question 10

True/False: atracurium and succinylcholine are more like to cause histamine release.

Answer 10

True

Question 11

Which of the following NMBDs is a depolarizing NMBD?

Atracurium
Cisatracurium
Succinylcholine
Rocuronium
Vecuronium

Answer 11

Succinylcholine

Question 12

What type of NMBD are atracurium, cisatracurium, rocuronium, and vecuronium?

Answer 12

Intermediate-acting (10-30 min) non-depolarizing NMBDs

Question 13

What is the Phase-1 block of succinylcholine?

Answer 13

Sustained muscle membrane depolarization initially leads to muscle fasciculation, then the post junctional Na channels close and remain closed until SCh is present, preventing neuromuscular transmission

Question 14

What is the Phase-2 block of SCh?

Answer 14

Similar to the non-depolarizing blockade; occurs after prolonged or high dose of SCh administration

Question 15

What are adverse effects of SCh?

Answer 15

Cardiac arrhythmias; hyperkalemia; fasciculation, myalgia, myoglobinuria; elevated intra-ocular and intra-gastric pressures; may trigger malignant hyperthermia

Question 16

What is the major metabolite of atracurium, and what does it cause?

Answer 16

Laudanosine; may cause seizures

Question 17

True/False: atracurium may cause histamine release at high doses.

Answer 17

True

Question 18

What is used to antagonize rocuronium?

Answer 18

Sugammadex

Question 19

True/False: rocuronium recovery is relatively slow.

Answer 19

False. Recovery is fast.

Question 20

How do you monitor neuromuscular function when using NMBDs?

Answer 20

Monitoring with peripheral nerve stimulators is necessary

Question 21

What is an acceptable neuromuscular recovery from NMBDs?

Answer 21

TOF ratio >/= 0.9

Question 22

True/False: peripheral nerve stimulators are commonly combined with an accelerometer.

Answer 22

True. Accelerometer quantifies the extent of movement.

Question 23

What sites are used for stimulation with a peripheral nerve stimulator?

Answer 23

Dogs and cats: peroneal and ulnar nerves

Horses: facial and peroneal nerves

Question 24

What are the two stimulation patterns used?

Answer 24

Single twitch and Train of four (TOF)

Question 25

What is the single twitch stimulation pattern?

Answer 25

Used at 1 Hz before injecting NMBD to determine the minimum necessary current to evoke maximal movement response; called supra maximal stimulus

Question 26

What is the TOF stimulation pattern?

Answer 26

Four stimuli following each other; with complete blockade, no response at all; with partial blockade, first twitch is largest and the last is smallest; ratio between first and last twitch is the TOF ratio

Question 27

True/False: it is generally safe to antagonize a depolarizing NMBD.

Answer 27

False. Antagonizing a depolarizing NMBD is unpredictable and not recommended.

Question 28

What is used to antagonize a non-depolarizing NMBD?

Answer 28

Acetylcholinesterase inhibitors (edrophonium, neostigmine)

Question 29

Which AChE inhibitor is preferred, and why?

Answer 29

Edrophonium is preferred over neostigmine because there are less side effects

Question 30

What is Sugammadex?

Answer 30

Chelating agent used for reversal of rocuronium.