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I & M II > NMB Monitoring > Flashcards

NMB Monitoring Flashcards

1
Q

How can the skeletal muscle be made to relax?

A

Interfering with transmission along the nerve trunk blocks signals from reaching the terminal bouton (local anesthetics)

Presynaptic - Interfering with Ach production, storage or release (hemicholinium, botulinus toxin, pentamethonium, NMBAs)

Synaptic Cleft – Inactivate neurotransmitter

Postsynaptic – Interfere with depolarization or activation of the end-plate (NMBAs)

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2
Q

What techniques do we use to record/monitor muscle function?

A

Observation (qualitative), visual, tactile
Mechanomyography (MMG, force displacement)
Electromyography (EMG)
Acceleromyography (AMG)
Kinemyography (KMG)

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3
Q

How many alpha subunits are located on an adult nicotinic receptor to convert the channel to an open state?

A

2

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4
Q

The fetal nicotinic receptors, following major stress, is characterized by a single subunit substitution. These receptors are characterized by a 10-fold increase in ionic activity, rapid metabolic turnover, and extrajunctional proliferation, thus what must be be cautious of doing?

A

giving Sux to these pts due to hyperkalemia

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5
Q

Pulse duration must be less than ____ msec so as not to induce repetitive neural firing or direct muscle stimulation.

A

0.5

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6
Q

What is supramaximal current?

A

10-20% above the current needed to stimulate all nerve fibers in the bundle

Note: This is readily achieved with needle electrodes less than 10mA.

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7
Q

Stimulation of all nerve fibers within a bundle is easily done with ____ electrodes, but ______ electrodes may fail to stimulate all fibers when they are not in close proximity to the nerve or when the pts are obese.

A

needle

surface

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8
Q

Needle electrodes require lower stimulation because they bypass impedance of the skin.

What is the low output level of needle stimulators?

What is the risk associated with high current density?

A

0-40mA

Hazard for electrical burns

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9
Q

Why is the distance b/n electrodes important?

A

Determines the penetration of depth of the stimulation current

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10
Q

How far should the electrodes be apart from one another?

A

1 inch

One source says 3-6 cm, other says 2.5-4cm.

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11
Q

What method of monitoring uses a force transducer similar to a BP transducer used to measure the force produced or the distance moved?

A

mechanical transduction (MMG)

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12
Q

What method uses electrodes, monitor the electrical activity induced in muscle by contraction – similar to ECG?

A

Electromyography (EMG)

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13
Q

What method of monitoring muscle function measures the acceleration of the muscle body or the attachment of the muscle?

A

Acceleromyography (AMG)

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14
Q

What method of monitoring muscle function uses motion that is converted to electricity?

A

Kinemyography (KMG)

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15
Q

What method does this depict?

A

Mechanical MG (MMG)

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16
Q

What method does this depict?

What is encircled?

A

EMG

detection electrode

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17
Q

What muscles are stimulated with ulnar nerve stimulation?

A

adductor pollicis

flexor pollicis brevis

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18
Q

Label

A
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19
Q

What type of neuromuscular blockade produces this response?

A

Non-depolarizing or Phase II block

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20
Q

What type of neuromuscular blockade produces this response?

A

depolarizing

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21
Q

What anatomical positions are suitable for monitoring?

A

Ulnar Nerve innervating Adductor pollicis and Flexor Pollicis Brevis

Facial Nerve innervating Frontalis and Orbicularis Oculi

Posterior Tibial innervating Flexor Hallucis Brevis

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22
Q

What 2 things should you not do during anode/cathode placement?

A

Do not place anode (red) between the cathode (black) and the muscle bed being observed.

Do not place the electrodes directly over muscle

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23
Q

Anodal current threshold is approx. ____% more than cathodal.

A

25

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24
Q

What movement is expected with ulnar nerve stimulation?

A

thumb adduction, 5th digit movement

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25
Q

What movement is expected with posterior tibial nerve stimulation?

A

Plantar flexion of the big toe

26
Q

What movement is expected with peroneal nerve stimulation?

A

Foot dorsiflexion

27
Q

What movement is expected with facial nerve stimulation?

A

orbicularis oculi contraction

28
Q

What movement is expected with mandibular nerve (V3) stimulation?

A

jaw closure

29
Q

A maximal dose of rocuronium has a faster onset time than a submaximal dose.

However, what can we say about the maximal effect with respect to time with a maximal and submax dose?

A

Both maximal and submaximal doses have a maximal effect at 4 minutes.

30
Q

Onset for neuromuscular blockade is faster for _____ potent drugs. Name the 2 common ones.

A

less

Sux, Roc

Note: More potent Vec and Cis take longer.

31
Q

When the adductor pollicis is maximumally blocked 98% +/- 1, how much are the laryngeal adductors blocked?

A

77% +/-5

32
Q

Label the recovery from NMB curves:

A
33
Q

Should nerve stimulation be monophasic or biphasic?

A

monophasic

34
Q

The evoked tension of the muscle varies with the stimulating current and forms a ________ curve.

A

sigmoidal

Note: As current increases, the number of nerves reaching threshold increases until all are responding. After all nerves have reached threshold, further increases in current fail to increase motor response.

35
Q

What initial threshold in mA is needed for stimulation?

What is the mA needed for supramaximal stimulus?

A

15 mA

32 mA

36
Q

Stimulation at 10mA will produce same fade response at 60mA. True or false?

A

True

Takeaway: We want to use the min. current to assess required stimulation.

37
Q

If you have a depolarizing block and initiate a post-tetanic stimulation, what response do you expect?

A

None

38
Q

If you have a non-depolarizing block, and initiate a post-tetanic stimulus, what response do you expect?

A

A stronger response than initial response

39
Q

What type of response is depicted?

A

Post-tetanic non-depolarizing block

40
Q

What type of response is depicted?

A

Post-tetanic depolarizing block

Note: The amplitude does not change after post-tetanic stimulus.

41
Q

What should the current output for a nerve stimulator be adjustable to?

A

from 10 - 80 mA

42
Q

As pulse duration becomes greater than ____ msec, muscle stimulation becomes more likely.

A

0.2 msec

43
Q

What % receptors are blocked for 4 TOFc, sustained tetany at 50Hz?

A

70%

44
Q

What % of receptors are blocked for 4 TOFc, onset of fade at 100Hz?

A

50%

Note: Measuring at 100Hz rather than 50Hz provides a 20% margin of safety when determining extent of NMB.

45
Q

There is no discernible decrease in the amplitude of the evoked neuromuscular response until at least _____% of receptors are blocked.

A

70

46
Q

How many post-tetanic twitches = 1 TOFc?

A

10

47
Q

When reversing the pt with no twitches, what chance of reversal do we have with a post-tetanic count of:

0
5-10
>10 count

A

0: little chance of reversal
5 – 10 count: possible reversal
>10 count: reversal very likely

The higher the count the more likely the reversal.

48
Q

If the TOF ratio = 0.7 - 0.75, what would be the correlating signs and symptoms?

A
  • Diplopia
  • Decreased grip strength
  • Inability to maintain apposition of the incisor teeth
  • Tongue depressor test negative
  • Inability to sit up without help
  • Severe facial weakness
  • Speaking is difficult
  • Overall weakness/tiredness
49
Q

What are unreliable tests for post-op neuromuscular recovery? (6)

A
  • Sustained eye opening
  • Protrusion of the tongue
  • Arm lift to the opposite shoulder
  • Normal tidal volume
  • Normal or early normal vital capacity
  • Max. inspiratory pressure less than 40-50 cmH2O
50
Q

What are the most reliable test of post-op neuromuscular recovery? (4)

A
  • Sustained head lift for 5 sec
  • Sustained leg lift for 5 sec
  • Sustained handgrip “ “
  • Max inspiratory pressure 40-50 cm H2O or greater
51
Q

If a pt is able to sustain a 5 sec head lift, what is the approximate TOF ratio?

A

0.6-0.7

52
Q

What are conditions associated with upregulation of ACh receptors? (7)

A
  • Spinal cord injury
  • Stroke
  • Burns
  • Prolonged immobility
  • Prolonged exposure to NMB
  • MS
  • Guillain-Barre syndrome
53
Q

What kind of response do you expect for those that have upregulated ACh receptors to nondepolarizing relaxants?

A

resistance to nondepolarizers

sensitivity to depolarizers

54
Q

What situations are associated with downregulation of ACh receptors?

A

myasthenia gravis

organophosphate poisoning

anticholinesterase poisoning

55
Q

What type of response do you expect with those that have downregulated ACh receptors?

A

very sensitive to NMDB

Blocking agents should be avoided.

Note: Chronic elevations of ACh observed with organophosphorus poisoning or chronic use of reversible cholinesterase inhibitors results in down-regulation of AChRs.

56
Q

What drugs potentiate the action of non-depolarizers?

A

Antibiotics (aminoglycosides) like gentamicin, tobramycin, amikacin

Lidocaine or other locals

Ca channel blockers

Beta blockers

Diuretics

57
Q

What inhalational agents produce the most–> least motor blockade?

A

Least soluble produce greatest blockade

Des>sevo>iso>halo > TIVA

58
Q

Hyper/hypo-thermia significantly prolongs the onset and duration of NMB.

A

hypothermia

59
Q

Stimulation electrodes should not take up a contact area greater than ___-____ mm.

A

7-11 mm

60
Q

The fading common after non-depolarizing relaxants is not observed when:

A

the direct stimulation of the muscle is occurring

additionally weak contractions continue even during deep motor blockade

61
Q

Reversal of NMB causes what 6 things?

A

BLUDS (BBLUDS)
Bradycardia
Bronchospasm
Lacrimation
Urination
Defecation
Salivation

62
Q

What is a neostigmine block?

A

Too much ACh results in the motor end plate to remain depolarized thus increasing block.

Thus reduce the dose of agent if recovery is almost complete.

I & M II (21 decks)

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