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Scientific Principles > Week 6 - Neuromuscular Blockade Monitoring > Flashcards

Week 6 - Neuromuscular Blockade Monitoring Flashcards

1
Q

What is the function of presynaptic nicotinic receptors?

A

Facilitate the recruitment of ACh
-normally in times of repeated muscle stimulation (like exercise) presynaptic nicotinic receptors are recruited to release more ACh

Non-Depolarizing drugs competitively block these receptors and inhibit recruitment of ACh (SUX usually does not)
-This causes the twitch fade

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2
Q

What is the determining factor as to whether a muscle will twitch or not with neuromuscular electrical stimulation?

A

Current

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3
Q

Define Maximal Current with neuromuscular electrical stimulation

A

If the nerve is stimulated with enough current all of the muscle fibers will contract

~30 mA

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4
Q

What current is typically used in neuromuscular electrical stimulation?

A

Usually a current just above maximal current is used to assure that all muscle fibers will fire

~50-60 mA (this hurts)

*do a baseline test to determine what the supramaximal current is as it may be more for those with DM or edema, or if there is increased resistance such as hair or poor skin contact (preform after they are asleep)

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5
Q

What is visual or tactile monitoring for neuromuscular electrical stimulation?

A

Qualitative, Subjective

  • You could just stimulate a nerve and then look at or feel if the muscle contracts
  • NOT reliable to assess detection of residual blockade
  • Patient may still have up to 70% 80% of their nicotinic receptors blocked and you may still feel or see a “strong” twitch
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6
Q

What type of neuromuscular electrical stimulation monitoring is objective and what type is subjective?

A

Objective: Quantitative NMT Monitoring

Subjective: Visual or Tactile Monitoring (Qualitative)

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7
Q

What are the different twitch patterns?

A
  • Single Twitch (no longer clinically relevant)
  • Double Burst (two short bursts of stimuli separated by 0.75 milliseconds – better able to “feel” a fade as the second response is weaker than the first response w/ residual blockade) (first twitch can be detected at deeper block levels than the first twitch of TOF)
  • Sustained Tetany (rapid repeated stimulus at 50-200Hz, results in more ACh release – look for fade with non-depolarizing block – depolarizing block the response will be weak but sustained)
  • Post Tetanic Count (Deep muscular blockade)
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8
Q

Describe the Single Twitch pattern of neuromuscular electrical stimulation

A

1.0Hz (once every 1 second) to 0.1Hz (once every 10 seconds)

  • Useful in determination of onset of action but not recovery of neuromuscular block
  • Requires baseline measurement of muscle response before administration of neuromuscular blocking drug
  • Does not differentiate depolarizing from non-depolarizing block (see faded response during onset of drug in both)
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9
Q

Describe the TOF pattern of neuromuscular electrical stimulation

A

2 Hz (4 stimuli every 0.5 seconds) – should not be repeated more frequently than 10-12 seconds

  • Useful for detection of neuromuscular block in range of surgical relaxation
  • During non-depolarizing block, allows for assessment of degree of block even when baseline value is absent
  • Allows for quantitative monitoring, which allows for accurate evaluation of TOF ratio and represents preferred method of assuring adequate muscle recovery (defined as TOF ratio > 0.9)
  • Depolarizing Drug response has decreased amplitude from baseline TOF with no fade
  • Non-Depolarizing Drug response has a muscle contraction fade
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10
Q

Describe the Tetanic Stimulation pattern of neuromuscular electrical stimulation

A

50 Hz for 5 seconds

  • Has fade equivalent to TOF fade
  • Has pattern of stimulation that is painful and therefore not appropriate for conscious patients
  • Depolarizing Drug response: sustained muscle response, but with decreased amplitude
  • Non-Depolarizing Drug response: fade observed in muscle response
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11
Q

Describe the Post-Tetanic Count pattern of neuromuscular electrical stimulation

A

Initial tetanic stimulation (50Hz for 5 sec), followed by 3 second pause, observation for presence of response of 1-Hz single twitch stimulation, followed by count of total number of single-twitch responses

  • Allows evaluation of degree of neuromuscular block when there is no response to single-twitch or TOF stimulation
  • Is inversely proportional to depth of non-depolarizing neuromuscular block

-Depolarizing Drug Response: not useful clinically
Non-Depolarizing Drug Response: tetanic stimulation is followed by a post-tetanic transient increase in muscle-twitch tension

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12
Q

Describe the Double Burst Stimulation pattern of neuromuscular electrical stimulation

A

Two bursts of three mini-tetanic 50-Hz stimuli separated by 0.75 seconds

  • Allows for slight qualitative (visual/tactile) improvement in evaluation of fade as compared with TOF induced fade but is still inadequate to ensure full neuromuscular recovery (TOF>0.9)
  • Has degree of fade that is equivalent to that of TOF stimulation
  • Depolarizing Drug Response: decreased amplitude from baseline with no fade in the two bursts
  • Non-Depolarizing Drug Response: second muscle contraction decreased as compared with the first response
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13
Q

TOF count vs TOF ratio

A

TOF count = how many twitches are present

TOF ratio = 1st twitch compared to the 4th twitch
-assessment of the quantity of a residual non-depolarizing block

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14
Q

What is the TOF pattern for a depolarizing blockade (SUX)? Phase I vs Phase II?

A

Phase I Block = no fade will be seen on TOF
-initial depolarization of the muscle end plate region, followed by flaccid muscle paralysis due to depolarization induced Na+ channel inactivation

Phase II Block = fade present on TOF
-with continuous admin at high concentrations or in the presence of atypical cholinesterase this can eventually be followed by the development of receptor desensitization

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15
Q

What are common TOF guidelines?

A

TOF 0.15-0.25 indicates adequate surgical relaxation

TOF > 0.9 is needed for safe extubation and recovery after surgery

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16
Q

What is the best nerve to use in neuromuscular electrical stimulation?

A

The Ulnar Nerve

  • Stimulate nerve and the response of the adductor pollicis muscle of the thumb is assessed for adduction
  • Easily located at the distal ulna
  • Low risk of mistaking direct muscle stimulus as nerve generated stimulus as nerve is far from the site of muscle contraction

*place negative (black) electrode on the distal patch

17
Q

When would you use the Posterior Tibial Nerve for neuromuscular electrical stimulation?
Where do you place the sensor?
What response do you monitor?

A

When hands or arms are not accessible

Easily located along the region of the medial malleolus

Assess the response of the flexor hallucis brevis (Big toe flexion)

18
Q

What muscle to you observe during Facial Nerve (CN VII) neuromuscular electrical stimulation?

A
  • Observe the corrugator supercilli muscle which causes the brow to furrow
  • Observe the orbicularis oculi that encircles the eye and causes the lid to close
  • NMB is similar to the adductor pollicus at the orbicularis oculi, but the supercilli muscle is much more resistant to NMDAs
  • Risk for direct stimulation as much less current is needed (use ~20 mA)
19
Q

List the relative sensitivity of muscle groups to non-depolarizing muscle relaxants from most resistant to most sensitive

A 
Most Resistant
     -Vocal Cord
     -Diaphragm
     -Orbicularis Oculi
     -Abdominal Rectus
     -Adductor Pollicis
     -Masseter
     -Pharyngeal (recovery doesn't occur until TOF >0.9)
     -Extraocular
Most Sensitive
20
Q

What are the different types of NMT Monitoring Technology?

A
  • Visual or Tactile (qualitative)
  • Accelormyography: measures how fast the muscle moves
  • Kinemyography: measures muscle movement
  • Electomyography: measures electrical activity
  • connect device before induction so you can get a baseline after the pt is asleep
  • dry electrode site free of hair
21
Q

Describe Accelomyography NMT monitoring

A

Measures how fast the muscle moves

  • Thin piezoelectrical transducer is fixed to the digit (thumb), when the digit moves a voltage proportional to the acceleration of the movement is generated
  • Easy to use, better than tactile estimate of the twitch
  • Hand needs to be IMMOBILIZED
22
Q

Describe Kinemyography NMT monitoring

A

Measures muscle movement

  • Flexible piezoelectric film sensor (between thumb and index finger)
  • When the material changes shape, the electrical charges change
  • The flow of charges is directly proportional to the amount of distortion
  • Hand does not need to be immobilized
  • Can measure TOF and anesthesia machines have the capability to display the results on the monitor
  • Only can be used for ULNAR nerve at the thumb
23
Q

Describe Electromyography NMT monitoring

A

Measures electrical activity – measures and relays action potential

  • Requires 3 electrodes over the insertion and/or the belly of the muscle
  • Used for research purposes
  • Susceptible to artifacts
  • More complex to use
24
Q

What is the dose of Sugammadex if there is no response to TOF?

A

16 mg/kg if the Post Tetanic Count is 0

4 mg/kg if the Post Tetanic Count is 1-15

25
Q

What is the dose of Sugammadex with a TOF count of 1-4 (with or without fade)?

A

2 mg/kg

26
Q

What is the dose of Sugammadex with a TOF ratio < 1.0?

A

2 mg/kg if TOF ratio < 0.9

No reversal if TOF ratio >/= 0.9

27
Q

What is the dose of Neostigmine with a TOF of 0-1?

A

Delay reversal till there is a TOF count of 2

28
Q

What is the dose of Neostigmine with TOF ratio <0.4 or TOF count 2-3?

A

0.05 mg/kg

29
Q

What is the dose of Neostigmine with TOF ratio 0.4 - 0.9?

A

0.02 mg/kg

30
Q

What is the dose of Neostigmine with TOF ratio >/= 0.9?

A

No reversal

31
Q

What is the dose of Neostigmine with TOF count 4?

A
  1. 04 mg/kg (with fade)

0. 02 mg/kg (with no fade)

Scientific Principles (16 decks)

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