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Sp: PMI > 13. PNS > Flashcards

13. PNS Flashcards

1
Q

nerve stimulators cause what to be released

A

Ach from the presynaptic nerve

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2
Q

what prevents Ach stockpile depletion

A

prejunctional Ach receptors

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3
Q

when will a muscle be unable to contract?

A

when 100% of the receptors are blocked

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4
Q

muscle relaxants ant Ach _________ bind __________ receptors

A

muscle relaxants and Ach competitively bind postjunctional receptros

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5
Q

what drug is better at reversing deeper levels of muscle relaxation?

A

sugammadex

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6
Q

what could happen if we were able to directly stimulate the muscle?

A

would cause an underestimation of how paralyzed a pt is

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7
Q

factors that cause direct muscle stimulation

A

> 80 mA current
pulse duration >500micro sec
electrodes on muscle instead of nerve

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8
Q

what is the pulse duration on nerve stimulatiors?

A

200 micro secs

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9
Q

what is the max current on nerve stimulators?

A

60-80mA

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10
Q

which nerve is it more common to incorrectly place electrodes?

A

facial nerve

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11
Q

5 types of nerve stim

A

single twitch
TOF
tetanus
post tetanic count
double burst stimulation

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12
Q

how are nerve stimulation patterns defined?

A

by the frequency in which they stimulate the motor nerve

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13
Q

single twitch

A

1 Hz (1/second)
or
0.1 Hz (1/10 seconds)

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14
Q

TOF

A

2 Hz

4 stimuli over 2 seconds

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15
Q

how long is each TOF stimuli?

A

0.2msec

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16
Q

how long is between each TOF stimuli?

A

500msec

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17
Q

tetanus

A

continuous nerve stimulation at 50-100Hz

flood NMJ w/max Ach resulting in sustained contraction

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18
Q

Post Tetanic Count

A

50Hz tetanus
5 seconds
3 second pause
single twitch at 1 Hz

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19
Q

Double Burst Stimulation

A

3 impulses at 50Hz
750 msec pause

either 2 impulses at 50Hz
or
3 impulses at 50 Hz

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20
Q

DBS 3,3

A

3 bursts at 50 Hz
750 msec pause
3 at 50 Hz

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21
Q

DBS 3,2

A

3 bursts at 50 Hz
750msec pause
2 bursts at 50 Hz

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22
Q

nerve stimulation frequency ranking

A

SLOWEST
Single Twitch
TOF
Tetanus
FASTEST

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23
Q

how long does each pulse duration (twitch) last?

A

0.2 msec
or
200 microsec

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24
Q

faster nerve stimulation frequencies ==

A

more Ach into NMJ

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25
Q

fade

A

something is causing less and less Ach to be released from the presynaptic nerve with each subsequent twitch

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26
Q

absence of fade

A

equal amount of Ach is released from presynaptic nerve on all twitches

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27
Q

fade requirements

A

partial neuromuscular block
must be non-depolarizing
faster nerve stim pattern

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28
Q

fade: Zero neuromuscular block

A

no fade
all twitches strong

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29
Q

fade: Total neuromuscular block

A

no fade
no twitches

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30
Q

what do nondepolarizers block?

A

presynaptic
and
postsynaptic

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31
Q

what do depolarizers block?

A

postsynaptic only

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32
Q

nondepolarizing block

A

less Ach released
fade observed

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33
Q

depolarizing block

A

equal Ach released
no fade released
overall twitch height decreased

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34
Q

what nerve patterns can show fade?

A

TOF
Tetanus
DBS
PTC

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35
Q

what nerve pattern cannot show fade?

A

single twitch

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36
Q

what frequency do you need to show fade?

A

> =2Hz

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37
Q

what does fade tell you?

A

how paralyzed the pt is

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38
Q

no fade means

A

pt is completely reversed

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39
Q

presence of fade means

A

pt is partially paralyzed

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40
Q

what is the gold std in assessment of recovery of neuromuscular blockade?

A

fade

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41
Q

is fade referring to onset or recovery or both?

A

recovery only

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42
Q

what nerve stim pattern can differentiate between depolarizing and nondepolarizing block?

A

TOF
Tetanus
PTC
DBS

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43
Q

what nerve stim pattern cannot differential between depolarizing and nondepolarizing?

A

single twitch

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44
Q

traditional nerve stimulators provide _______ data

A

qualitative

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45
Q

qualitative nerve stimulator
Max Output
Tetanus

A

max output: 70mA
tetanus: 100Hz

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46
Q

black electrode

A

negatively charged
depolarizes membrane

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47
Q

red electrode

A

positively charged
hyperpolarizes membrane

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48
Q

ulnar nerve electrode placement

A

red: proximal
black: distal

3-6cm apart

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49
Q

facial nerve electrode placement

A

red: forehead
black: zygomatic arch in front of ear

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50
Q

subthreshold stimulus

A

no motor units respondt

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51
Q

threshold stimulus

A

one motor unit responds

AKA initial threshold for stimulation (ITS)

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52
Q

submaximal stimuli

A

increasing number of motor units respond

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53
Q

maximal stimulus

A

all motor units respond

AKA pre-relaxant control response

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54
Q

supramaximal stimuli

A

all motor units respond

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55
Q

if you dont use enough current to stimulate the nerve….

A

you can produce a lower strength muscle contraction

weak twitches

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56
Q

what stimulus do we need to stimulate the nerve for maximum twitch height

A

supramaximal

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57
Q

what current usually stimulates maximum twitches?

A

40-60mA

58
Q

single twitch stimulation indications

A
  1. muscle relaxant onset
  2. determine supramaximal stimulus current
  3. post tetanic count
  4. continuous nerve stim to decr PONV
59
Q

can single twitch assess recovery of muscle paralysis?

A

NOPE

60
Q

single twich disadvantage

A

does not produce fade during recovery
cannot assess NMB recovery
cannot destinguish depolarizing vs nondepolarizing

61
Q

what will happen if you use single twitch to monitor muscle relaxant onset

A

twitches will gradually fade away

62
Q

what percentage of receptors must be blocked for twitches to start to fade away when monitoring with single twitch?

A

75%

63
Q

where do you place the PNS for PONV stimulation?

A

ulnar nerve (61% pts had PONV)

median nerve (45% pts had PONV)

use median nerve

64
Q

what accupuncture site is located on the median nerve?

A

P6

65
Q

what current should you stimulate for PONV

A

50mA on the median nerve through single twitch

66
Q

what are you comparing if you use single twitch to assess recovery?

A

max twitch height at end of case == max twitch height prior to muscle relaxant

67
Q

TOF can tell us

A

how profound the neuromuscular block is

68
Q

0 twitches

A

> 90% block

69
Q

1 twitch

A

90% block

70
Q

2 twitches

A

80% block

71
Q

3 twitches

A

75% block

72
Q

4 twitches

A

<75% block

73
Q

TOF ratio

A

strength of the 4th twitch compared to the first twitch

74
Q

higher TOF ratio

A

lower fade
stronger muscle function

75
Q

what TOF ratio is indicative of residual neuromuscular blockade?

A

<0.9

76
Q

TOF disadvantage

A

not as good at measuring “deep” levels of blockade

77
Q

tetanus advantage

A

assesses deeper levels of blockade

78
Q

sustained tetanus >5seconds indicates…

A

that the pts muscle paralysis has been adequately reversed

79
Q

disadvantage of tetanus

A

pain

80
Q

PTC

A

assesses deepest level of paralysis

81
Q

lower number of Post tetanic twitches

A

longer wait for twitch return

15-20 mins

82
Q

higher number of post tetanic twitches

A

shorter wait for twitch return

83
Q

when can you reverse with neostigmine

A

PTC of 10+
or 2-3 muscle twitches

84
Q

tetanus increases

A

total Ach in the synapse

larger contraction

85
Q

double burst stimulation advantage

A

easier to see fade with naked eye

86
Q

why do you wait between re-stimulating a nerve?

A

if you dont wait, it will produce a stronger muscle contraction
so you will underestimate the neuromuscular block

87
Q

what pattern do you use for supramaximal stimulus?

A

single twitch

88
Q

what pattern is good at assessing muscle relaxant onset?

A

sing twitch

89
Q

what pattern is good at assessing partial blockade and recovery from blockade?

A

TOF
tetanus
PTC
DBS

90
Q

what pattern differentiates between depolarizing and nondepolarizing?

A

TOF
tetanus
PTC
DBS

91
Q

what patter can assess deep levels of blockade?

A

tetanus
PTC
DBS

92
Q

time between TOF stimulations

A

10-30s

93
Q

time between DBS stimulations

A

12-15s

94
Q

time between tetanic stimulations

A

2 mins

95
Q

time between PTC stimulations

A

6 mins

96
Q

recovery of muscles order

A
  1. diaphragm
  2. rectus abdominus
  3. laryngeal adductors
  4. orbicularis oculi
  5. adductor pollicis
97
Q

which nerve site is the best for determining onset time for intubation?

A

facial nerve
(orbicularis oculi)

98
Q

facial nerve approximates

A

laryngeal adductors

99
Q

which nerve site gives best confidence that breathing muscles are recovered?

A

ulnar nerve

100
Q

direct muscle stimulation is most likely on what nerve

A

facial nerve

101
Q

alternate nerve monitoring site

A

posterior tibial nerve

102
Q

neostigmine dosing: 4 twitches w/o fade

A

0-1 mg neostigmine

103
Q

neostigmine dosing: 4 twitches w/fade

A

1-2 mg neostigmine

104
Q

neostigmine dosing: 2-3 tiwtches

A

2-3 mg neostigmine

105
Q

neostigmine dosing: 1-2 twitches

A

4-5 mg neostigmine

106
Q

sugammadex dosing: 4/4 w or w/o fade

A

1mg/kg

107
Q

sugammadex dosing: 2/4 or 3/4

A

2 mg/kg

108
Q

sugammadex dosing: 1/4

A

3 mg/kg

109
Q

sugammadex dosing: 0/4 w/1 twitch post tetanus

A

4 mg/kg

110
Q

sugammadex dosing: 0/4 and no post tetanic twitch

A

wait

111
Q

what dose of Roc is needed to re-paralyze the pt?

dose of sugammadex: <4mg/kg
>= 4 hrs ago

A

0.6mg/kg

112
Q

what dose of Roc is needed to re-paralyze the pt?

sugammadex: 4 mg/kg
<= 5 mins

A

1.2 mg/kg

113
Q

when do you have to wait 24 hrs after sugammadex to re-use Roc?

A

if 16 mg/kg dose was used
renal insufficiency/failure pts

114
Q

what can you use instead of Roc to re-paralyze the pt?

A

Cisatracurium (nimbex)

115
Q

indicators of adequate reversal

A

sustained head lift (5 sec)
sustained tetanus (>5 sec)
tidal volume (5-10 mL/kg)
strong grip
NIF (-50 to - 100 cmH2O)
TOF ratio

116
Q

NIF

A

the greatest negative pressure a pt can generate during inspiration

117
Q

what NIF means a pt is extubatable?

A

-20 to -30 cmH2O

118
Q

what NIF indicates adequate reversal but no airway protection?

A

-25cmH2O

119
Q

what NIF indicates adequate reversal w/airway protection?

A

-30 cmH2O

120
Q

what is the most reliable indicator of adequate reversal

A

TOF ratio

121
Q

TOF ratio >0.75

A

5 sec head lift
sustained tetanus >5 s
cough
NIF -25 cm/H2O

122
Q

TOF ratio >0.9

A

pts can sit up unassisted
normal pharyngeal function

123
Q

TOF ration <0.9

A

risk of aspiraiton

124
Q

Physiologic factors that prolong duration of MR

A

hepatic disease
renal disease
hypothermia
increased age
MG
premature neonates
acidosis

125
Q

electrolyte abnormablites that prolong duration of MR

A

hypocalcemia
hypercalcemia
hypomagnesemia
hypermagnesemia
hypokalemia
hypernatremia

126
Q

meds that prolong duration of MR

A

aminoglycoside antibiotics (gentamicin)
inhalational agents
local anesthetics
ca channel blockers (verapamil)
antiarrythmics (diltiazem)
lithium (prolongs sux)
sux (prolongs NDMR)

127
Q

phase II block

A

depolarizing block that resembles a nondepolarizing block

128
Q

causes of phase II block

A

larger dose of sux (>6mg/kg)
sux redosing or infusion

129
Q

how do you reverse a phase II block

A

neostigmine
or waiting

130
Q

awake extubation advantages

A

less risk of obstruction
less risk of laryngospasm
protected airway

131
Q

awake extubation disadvantages

A

coughing
bronchospasm
slow turn over time

132
Q

awake extubation criteria

A

spotaneous ventilation
strong enough to breath
responds to commands

133
Q

deep extubation

A

extubates when pt is spontaneously breathing but fairly anesthetized

134
Q

deep extubation advantages

A

less likely to cough
faster OR turnover time

135
Q

what surgeries might you want a deep extubation?

A

hernia
nasal septoplasty
tonsillectomy

136
Q

deep extubation disadvantages

A

airway not protected
airway obstruction
laryngospasm

137
Q

deep extubation absoluted contraidications

A

uncontrolled GERD
full stomach
hiatal hernia
difficult airway
airway edema

138
Q

deep extubation criteria

A

sponteneously breathing
adequate tidal volumes
truly deep
thoroughly suctioned

139
Q

deep extubation relative contraindications

A

obesity
OSA

140
Q
A

Sp: PMI (18 decks)

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