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Anesthesia Equipment > NMBA monitoring > Flashcards

NMBA monitoring Flashcards

1
Q

Explain neuromuscular transmission

A

Impulse arrives at motor end plate causing release of ACh from vesicles (Calcium causes exocytosis), ACh diffuses across synapse - binds to receptors on sarcolemma, binding of ACh causes sodium to enter cell and cause depolarization, then sarcolemma repolarizes by potassium leaving and sodium/potassium pump restoring polarity- ACh is broken down by AChE

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2
Q

NMBA action (general)

A

Prevents ACh to bind to receptors which prevents neurally-mediated muscle membrane depolarization & subsequent muscle contraction

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3
Q

How many ACh-receptors need to be activated to cause depolarization

A

Only about 20% (which means 80% can be blocked and can’t tell the different in contraction)

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4
Q

Supramaximal stimulus - defined & how much

A

Stimulating curent to peripheral nerve that is sufficient to cause all NMJ of that nerve to release ACh, in adults usually 30-50 mA

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5
Q

What happens with the nerve stimulus above supramaximal?

A

Will not get any more muscle contraction

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6
Q

Tetanic stimulation

A

sustained- whole hand contracts and relaxes after ACh has run out

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7
Q

Post-tetanic count stimulation

A

50 Hz tetanic stim for 5 sec, wait 3 sec than supramaximal stimulus at 1 Hz - this stimulates more ACh (see twitches when you normally wouldn’t)- if 5-7 responses are detectable after tetanic stimulation - return of TOF response is imminent

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8
Q

Train of Four stimulation defined

A

4 supramaximal neural stimuli at 2 hertz causing 4 sequential muscular contraction (a little less ACh is released with each stimulus)

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9
Q

How many receptors are blocked with loss of 4th response in TOF?

A

75-80%

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10
Q

How many receptors are blocked with all 4 twitches in TOF monitoring?

A

No more than 20%

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11
Q

How many receptors are blocked with loss of 3rd response in TOF?

A

85%

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12
Q

How many receptors are blocked with loss of 2nd response in TOF?

A

90%

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13
Q

How many receptors are blocked with loss of 1st response in TOF?

A

98-100%

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14
Q

What is TOF ratio?

A

Amplitude of 4th twitch divided by amplitude of 1st twitch. If >70-80%, no more than 20% receptors should be blocked

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15
Q

Double Burst Stimulation

A

2 sequential bursts of 3 impulses and then 2 impulses at 50 Hz with an interval of 750 msec, a fade of the 2nd impulse compared with first correlates with incomplete NMBA recovery with TOF ratio <0.6

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16
Q

6 measures of muscle response to nerve stimulation

A

Electromyography (depolarization), mechanomyography (contraction), acceleromyography (contraction), kinemyography (contraction), phonomyography (contraction), & visual/tactile assessments (contraction).

17
Q

Electromyography - what it is

A

Based on measurement of muscle compound action potential that occurs with muscle membrane depolarization (electrical*)

18
Q

EMG amplitude

A

about 20 mV, does not change with repeated stimulation– give stimulus & stimulus is then measured

19
Q

What is mechanomyography

A

Based on isometric measurement of muscle force (no change in length)

20
Q

How to use mechanomyography

A

Use ulnar nerve to stimulate adductor pollicus. *Used in research

21
Q

What is acceleromyography

A

Based on isotonic measurement of acceleration of thumb (the muscle force is proportional to muscle acceleration - a transducer -piezoelectric- placed over muscle innervated- measures acceleration). *This can only be used on adductor pollicus and hand must be able to move freely, also force changes with repeated stimulation (stair-stepping)

22
Q

What is kinemyography?

A

Measurement of thumb movement in response to nerve stimulation

23
Q

What is phonomygraphy?

A

Contracting muscle evokes sounds of 4-5 Hz, use microphone over thenar region or first dorsal interosseus muscle in research

24
Q

Visual/tactile evaluation of TOF ratio

A

Clinicians not able to detect TOF fade >0.4, only know if paralytic is on or none at all

25
Q

Visual/tactile evaluation of tetanic fade

A

Not able to detect fade if TOF ratio >0.4, if fade is present, residual paralysis is likely - if fade is absent, it does not prove paralytic is absent

26
Q

Non-nerve stimulation techniques for NMBA

A

Sustained head lift (5 sec) - able to be complete with partial paralytic (if patient cannot sustain head lift, residual paralysis is likely, but if they can it does not mean paralysis is absent). Tongue depressor - if patient cannot keep between teeth residual paralysis is likely, if can does not prove paralysis is absent

27
Q

Ulnar nerve innervation

A

Stimulation of ulnar does not produce movement of only the thumb but also every other finger- easy to underestimate neuromuscular blockade because adductor pollicus is most sensitive DO NOT FOLLOW OTHER HAND MUSCLES - WILL GIVE TOO MUCH

28
Q

Corrugator supercilii monitoring NMBA

A

Patches at lateral eyebrow, will see motion on medial half of superciliary arch– more resistant to muscle relaxants

29
Q

Orbicularis oris monitoring NMBA

A

Place electrodes lateral to the orbit - motion will be on lateral half of upper eyelid- more like adductor policus

30
Q

What should your TOF ratio be to determine paralytic is effectively worn off?

A

0.9 - less than that are associated with functional impairment of muscles of pharynx and upper esophagus= aspiration, can also have critical respiratory events. Should be at least 0.8!

31
Q

NMBA reversal efficacy

A

Neostigmine is limited- with high levels of paralytic 100% inhibition of acetylcholinesterase may still not be sufficient to compete with paralytic from acetycholine receptor.

32
Q

Max acetylcholinesterase inhibition neostigmine dose

A

50-70 mcg/kg

33
Q

How long will it take for neostigmine to work if only 1 detectable response from TOF

A

20 minutes to restore TOF to 0.8

34
Q

How long will it take for neostigmine to work if 2 detectable responses from TOF

A

15 minutes

35
Q

When can prompt (<10 minutes) reversal of paralytics occur?

A

4 responses to TOF

Anesthesia Equipment (18 decks)

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