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Pharmacology 680 > Physiology and Monitoring Neuromuscular Blockade > Flashcards

Physiology and Monitoring Neuromuscular Blockade Flashcards

(60 cards)

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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
- titration of dosage of NMB to desired effect - monitor for unusual resistance or sensitivity - evaluate reversibility - determine recovery from block
objectives of clinical monitoring
26
how do we know prejunctional receptor activity?
TOF monitoring
27
how long do you do the tetunus
5 seconds is standard up to 10
28
how do you monitor NMB?
by electrical stimulation of the peripheral motor nerve to observe the muscular contractions in response
29
Two most common locations to check TOF?
ulnar nerve and facial nerve
30
- 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
ulnar nerve
31
located behind medial maleolus of the tibia and posteromedial to the pt artery -causes plantar flexion of big toe when stimulated
posterior tibial nerve
32
- located behind the head of the fibula and around neck of fibula - foot will dorsiflex
lateral popliteal or peroneal nerve
33
lies within the parotid gland after it emerges from the stylomastoid foramen
facial nerve [place electrodes close to the tragus of the ear]
34
stimulation of facial nerve causes response in
orbicularis oculi
35
greater density of ACh receptors causes less dense block and more rapid recovery
orbicularis oculi
36
onset time
- small rapidly moving muscles (eyes, fingers) - trunk, abdominal muscles, long muscles - intercostal and diaphragm
37
recovery time
- diaphragm first to recover - rapidly moving muscles - long muscles
38
- inability to focus vision, keep eyelids open, double vision - inability to swallow - inability to phonate - hearing acuity intensified
first signs of relaxation
39
the delivery of four stimuli at a frequency of 2 Hz (4 stimuli in 2 seconds)
train of four (TOF)
40
technique relies on the reduction of ACh release with rapid rates of stimulation must wait 10 seconds before repeat
TOF
41
TOF Recovery of 2/4 means ___ receptors blocked
90%
42
TOF recovery 3/4 means ___ receptors blocked
80%
43
TOF recovery of 4/4 means __ receptors blocked
70-75% (still potentially clinically blocked)
44
clinical relaxation requires what % blocked
75-90%
45
difficult to detect TOF fade when ratio is __ or >
0.4
46
if no fade, only 50% chance that true TOF is >__
0.6 [pt could still have signs of residual block post extubation]
47
all 4 twitches are reduced, will not see a fade
depolarizing block
48
TOF ratio decreases or fades and is inversely proportionate to the degree of of block [if TOF 4/4 less blocked then 1/4]
nondepolarizing block
49
when administering SCh, fade occurs
phase II block
50
two short bursts of 3 stimuli at frequency of 50 Hz prob wont do clinically easier to detect fade
double burst
51
- stimulation of 50 Hz to 100 Hz - used to assess recovery - wait 10 mins between assessments
tetanic stimulation, or tetanus
52
what is appropriate TOF to give reversal
1/4
53
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]
posttetanic twitch
54
how many posttetanic twitches coincide with 1/4 TOF
10
55
requires baseline before drug admin, generally used as qualitative and not quantitative
single twitch
56
reflects blockage from 70-100%, useful during onset, maintenance, and emergence but really maintenance best
TOF
57
should be used sparingly for deep block assessment
tetanus
58
used only when TOF or double burst stim response is absent, count <8 indicated deep block and prolonged recovery
posttetanic
59
adequate reversal may take as long as 30 mins
1/4 TOF
60
recovery may take 4-12 mins
2/4 or 3/4 twitches

Pharmacology 680 (19 decks)

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