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Pharmacology 680 > Physiology and Monitoring Neuromuscular Blockade > Flashcards

Physiology and Monitoring Neuromuscular Blockade Flashcards

1
Q

prevents muscle contraction by interfering with the transmission of an action potential from the nerve ending to the muscle

A

action of neuromuscular blockers

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2
Q
  • facilitate intubation
  • decrease muscle tone to provide appropriate operating conditions
  • alleviate muscle activity with ECT
  • allow balance anesthesia w/o pt movement
  • assist in controlled vent pts
A

uses of neuromuscular blockers

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3
Q
  • impulse arrives at the motor nerve terminal
  • Ca influx release ACh into cleft (synapse)
  • ACh diffuses across cleft to nicotinic receptor
  • ACh binds with alpha sites on postsynaptic receptor causing ion channel to open
  • Na and K ions move across channel causing depolarization
  • action potential spreads over surface of muscle fibers causing contraction
  • ACh diffuses away from end plate region or is metabolized by acetylcholinesterase (AChE)
A

normal neuromuscular function

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4
Q

release of acetylcholine is ___ dependent and triggered by increases in concentrations of free ___ ions in nerve terminals

A

Calcium

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5
Q

opens calcium ion channels

A

cyclic adenosine monophosphate (cAMP)

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6
Q

what is the primary neurotransmitter?

A

acetylcholine

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7
Q

the principle site of action of neuromuscular blocking agents
“site of effect”

A

neuromuscular junction

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8
Q

what inhibits release of ACh

A

magnesium

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9
Q

synthesized in the motor nerve ending by acetylation of choline which is controlled by choline acetylase enzyme

A

acetylcholine

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10
Q

what is ACh rapidly (<15 ms) hydrolyzed by turning it into choline and acetic acid where choline is taken back into nerve ending to be used to synthesize more ACh

A

acetylcholinesterase (AChE)

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11
Q
  • on nerve ending
  • affects neurotransmitter release
  • ion channel allow flow of Na
  • activation mobilizes additional ACh for release
A

ACh presynaptic (prejunctional) receptors

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12
Q

blockade of presynaptic (prejunctional) receptors causes a __ in the release of ACh

A

decrease

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13
Q
  • similar to those found in fetus
  • receptors found throughout muscle cell, as call matures, less are formed
  • not involved in neuromuscular transmission
  • sensitive to agonists AND channels remain open 4x longer (hyperkalemia)
  • creating supressed by nerve ending activity
A

extrajunctional (perijunctional) receptors

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14
Q

occurs if the muscle is damaged, diseased or denervated (burns, paralysis, stroke, muscular dystrophies, immobilization)

A

proliferation of extrajunctional receptors

[means there are more places NMB can attach to but will not have same effect]

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15
Q
  • in junctional folds of muscle membrane
  • made of 5 linear protein subunits (2 alpha, beta, delta, and epsilon)
  • form a channel for flow of Na, K, Ca
A

postsynaptic receptors

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16
Q
  • ACh binds to extracellular sites on alpha subunits
  • channel opens
  • Ca and Na flow in, K out
  • depolarization occurs
  • muscle contraction
A

postsynaptic receptor events

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17
Q

attaches to both alpha subunit sites and mimics ACh and causes depolarization

A

depolarizing blockers

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18
Q

attaches to one alpha subunit to prevent ACh from binding and thus prevents depolarization

A

nondepolarizing blocks

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19
Q

can occur with antibiotics (mycins), quinidine, tricyclic antidepressants, and naloxone
physically blocks an open channel or a closed channel around the extracellular entrance

A

closed channel blockade

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20
Q

time from administration to max effect

A

onset time

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21
Q

time from admin to 25% recovery of twitch response (1/4 TOF)

A

clinical duration

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22
Q

time from admin to 90% recovery of twitch respone

A

total duration

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23
Q

time from 25% to 75% recovery of twitch responses

A

recovery index

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24
Q

the dose needed to produce 95% of suppression of single twitch response

A

ED 95

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25
Q
  • titration of dosage of NMB to desired effect
  • monitor for unusual resistance or sensitivity
  • evaluate reversibility
  • determine recovery from block
A

objectives of clinical monitoring

26
Q

how do we know prejunctional receptor activity?

A

TOF monitoring

27
Q

how long do you do the tetunus

A

5 seconds is standard up to 10

28
Q

how do you monitor NMB?

A

by electrical stimulation of the peripheral motor nerve to observe the muscular contractions in response

29
Q

Two most common locations to check TOF?

A

ulnar nerve and facial nerve

30
Q
  • located lateral to the flexor carpi ulnaris tendon and medial to the ulnar artery
  • when stimulated causes adduction of thumb via adductor pollicis brevis muscle
A

ulnar nerve

31
Q

located behind medial maleolus of the tibia and posteromedial to the pt artery
-causes plantar flexion of big toe when stimulated

A

posterior tibial nerve

32
Q
  • located behind the head of the fibula and around neck of fibula
  • foot will dorsiflex
A

lateral popliteal or peroneal nerve

33
Q

lies within the parotid gland after it emerges from the stylomastoid foramen

A

facial nerve

[place electrodes close to the tragus of the ear]

34
Q

stimulation of facial nerve causes response in

A

orbicularis oculi

35
Q

greater density of ACh receptors causes less dense block and more rapid recovery

A

orbicularis oculi

36
Q

onset time

A
  • small rapidly moving muscles (eyes, fingers)
  • trunk, abdominal muscles, long muscles
  • intercostal and diaphragm
37
Q

recovery time

A
  • diaphragm first to recover
  • rapidly moving muscles
  • long muscles
38
Q
  • inability to focus vision, keep eyelids open, double vision
  • inability to swallow
  • inability to phonate
  • hearing acuity intensified
A

first signs of relaxation

39
Q

the delivery of four stimuli at a frequency of 2 Hz (4 stimuli in 2 seconds)

A

train of four (TOF)

40
Q

technique relies on the reduction of ACh release with rapid rates of stimulation
must wait 10 seconds before repeat

A

TOF

41
Q

TOF Recovery of 2/4 means ___ receptors blocked

A

90%

42
Q

TOF recovery 3/4 means ___ receptors blocked

A

80%

43
Q

TOF recovery of 4/4 means __ receptors blocked

A

70-75% (still potentially clinically blocked)

44
Q

clinical relaxation requires what % blocked

A

75-90%

45
Q

difficult to detect TOF fade when ratio is __ or >

A

0.4

46
Q

if no fade, only 50% chance that true TOF is >__

A

0.6

[pt could still have signs of residual block post extubation]

47
Q

all 4 twitches are reduced, will not see a fade

A

depolarizing block

48
Q

TOF ratio decreases or fades and is inversely proportionate to the degree of of block
[if TOF 4/4 less blocked then 1/4]

A

nondepolarizing block

49
Q

when administering SCh, fade occurs

A

phase II block

50
Q

two short bursts of 3 stimuli at frequency of 50 Hz
prob wont do clinically
easier to detect fade

A

double burst

51
Q
  • stimulation of 50 Hz to 100 Hz
  • used to assess recovery
  • wait 10 mins between assessments
A

tetanic stimulation, or tetanus

52
Q

what is appropriate TOF to give reversal

A

1/4

53
Q

consists of 3 sec 50 Hz tetanus, 3 sec pause, twitch stimuli at 1 Hz
can determine time it will take to get to 1/4 TOF
[would not do if you had 1/4> reading TOF]

A

posttetanic twitch

54
Q

how many posttetanic twitches coincide with 1/4 TOF

A

10

55
Q

requires baseline before drug admin, generally used as qualitative and not quantitative

A

single twitch

56
Q

reflects blockage from 70-100%, useful during onset, maintenance, and emergence but really maintenance best

A

TOF

57
Q

should be used sparingly for deep block assessment

A

tetanus

58
Q

used only when TOF or double burst stim response is absent, count <8 indicated deep block and prolonged recovery

A

posttetanic

59
Q

adequate reversal may take as long as 30 mins

A

1/4 TOF

60
Q

recovery may take 4-12 mins

A

2/4 or 3/4 twitches

Pharmacology 680 (19 decks)

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