6. NMBAs

Question 1

What are NMBAs

Answer 1

neuromuscular blocking agents

Question 2

When to re-dose

Answer 2

if re-dose is needed, use low dose titrated to effect (to centralize eye) Cannot recover a paralyzed patient, AchEi requires partial metabolism to reverse (3 twitches with TOF/spontaneous breathing)

Question 3

act on the ____ receptor at the ____

Answer 3

Nicotinic Ach at the NMJ

Question 4

effect of nmba?

Answer 4

paralysis (interrupt transmission at the NMJ)

only affects skeletal muscle

Question 5

Two different mechanisms?

Answer 5

1. Nondepolarizing
   - NO short acting
   - Intermediate acting: atracurium, rocuronium
   - we don’t use the long acting ones
2. depolarizing
   - succinylcholine (not used often)

Question 6

advantage over ach

Answer 6

only one molecule is needed to block receptor (competitive antagonist)

Question 7

termination of effect of nmba?

Answer 7

redistribution/metabolism/excretion

reversal agent - inc. Ach concentration

Question 8

two types of non depolarizing nmbas?

Answer 8

1. bensylisoquinolinium compounds
   - can cause H release
   - don’t rely on liver for metabolism, eliminated into blood and met with plasmatic esterases
   ex/ atracurium
2. steroidal compounds:
   - met by liver

Question 9

atracurium v. cis atracurium

Answer 9

atracurium is a mixture of 3 groups (cis is the most potent one)

• Laudanosine is liver toxic, product of hoffman elimination, causes seizures
• H release
• cis-atracurium needs much lower dose -> less H release and less laudonosine production

Question 10

Hoffman elimination is __ and ___ dependent

Answer 10

pH and temperature

without these, metabolism is prolonged

Question 11

vecuronium

Answer 11

metabolite has some nmba properties, met in liver

no H release

Question 12

rocuronium

Answer 12

derived by vecuronium, less potent, needs high dose, faster onset

Question 13

reversal of nondepolarizing nmbas

Answer 13

1. AchE inhibitors, they compete with NMBA at the NAch receptor, CANNOT be used to reverse a DEEP block
   - neostigmine, edrophonium
   - acts on MAchR -> bradycardia, bradyarrthythmia (pre-treat with atropine)
2. Encapsulating agents. Can reverse deep block, no CV effects, super expensive not used

Question 14

succinylcholine

Answer 14

• depolarizing NMBA
• two Ach molecules together, initially activates receptor and causes fasiculations
• followed by flaccid paralysis
  met by butrylcholinesterase (psuedocholineresterase)
• giant dose, fast
• used for ET in humans because quick and goes away fast
• tremors start in front and move to back

Question 15

side effects of succinylcholine

Answer 15

• MAchR - bradycardia or ANS ganglia - tachycardia/hypertension
• Hyper K
• Myoglobinuria (due to muscle contraction)
• inc. IOP (muscle contraction)
• MH

Question 16

only indication is

Answer 16

muscle relaxation

Question 17

often used for which surgeries?

Answer 17

• OCULAR surgery
  - different sensitivities (high is highly sensitive
• Fracture reduction
• improvement of surgical field
• preventing cough during intubation
• facilitation of mechanical ventilation
• C section (doesn’t cross placenta) provide analgesia
• rapid intubation in cat

Question 18

3 Rules of NMDAs

Answer 18

1. use with hypnotic and analgesic
2. use IPPV
3. Monitor anesthetic depth - ONLY with HR

Question 19

MAC awake

Answer 19

(0.8) half of that asleep (1.3)

Question 20

exclude ________ before extubating

Answer 20

residual paralysis

Question 21

how do we assess muscular response?

Answer 21

visual, tactile
MMG, EMG,
**AMG

Question 22

AMG

Answer 22

acceleromyography

Question 23

stimulation patterns - train of four (TOF)

Answer 23

T1/T4 is TOF ratio 100% is no paralysis (4 twitches)

*need 3 twitches to reverse

Question 24

reverse if patient is breathing?

Answer 24

yes! they can still be partially paralysed, reverse!

Question 25

anesthetic drugs can act ______ with NMBAs

Answer 25

synergistically! muscle relaxers!