13. PNS Flashcards
1
Q
nerve stimulators cause what to be released
A
Ach from the presynaptic nerve
2
Q
what prevents Ach stockpile depletion
A
prejunctional Ach receptors
3
Q
when will a muscle be unable to contract?
A
when 100% of the receptors are blocked
4
Q
muscle relaxants ant Ach _________ bind __________ receptors
A
muscle relaxants and Ach competitively bind postjunctional receptros
5
Q
what drug is better at reversing deeper levels of muscle relaxation?
A
sugammadex
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
7
Q
factors that cause direct muscle stimulation
A
> 80 mA current
pulse duration >500micro sec
electrodes on muscle instead of nerve
8
Q
what is the pulse duration on nerve stimulatiors?
A
200 micro secs
9
Q
what is the max current on nerve stimulators?
A
60-80mA
10
Q
which nerve is it more common to incorrectly place electrodes?
A
facial nerve
11
Q
5 types of nerve stim
A
single twitch
TOF
tetanus
post tetanic count
double burst stimulation
12
Q
how are nerve stimulation patterns defined?
A
by the frequency in which they stimulate the motor nerve
13
Q
single twitch
A
1 Hz (1/second)
or
0.1 Hz (1/10 seconds)
14
Q
TOF
A
2 Hz
4 stimuli over 2 seconds
15
Q
how long is each TOF stimuli?
A
0.2msec
16
Q
how long is between each TOF stimuli?
A
500msec
17
Q
tetanus
A
continuous nerve stimulation at 50-100Hz
flood NMJ w/max Ach resulting in sustained contraction
18
Q
Post Tetanic Count
A
50Hz tetanus
5 seconds
3 second pause
single twitch at 1 Hz
19
Q
Double Burst Stimulation
A
3 impulses at 50Hz
750 msec pause
either 2 impulses at 50Hz
or
3 impulses at 50 Hz
20
Q
DBS 3,3
A
3 bursts at 50 Hz
750 msec pause
3 at 50 Hz
21
Q
DBS 3,2
A
3 bursts at 50 Hz
750msec pause
2 bursts at 50 Hz
22
Q
nerve stimulation frequency ranking
A
SLOWEST
Single Twitch
TOF
Tetanus
FASTEST
23
Q
how long does each pulse duration (twitch) last?
A
0.2 msec
or
200 microsec
24
Q
faster nerve stimulation frequencies ==
A
more Ach into NMJ
25
fade
something is causing less and less Ach to be released from the presynaptic nerve with each subsequent twitch
26
absence of fade
equal amount of Ach is released from presynaptic nerve on all twitches
27
fade requirements
partial neuromuscular block
must be non-depolarizing
faster nerve stim pattern
28
fade: Zero neuromuscular block
no fade
all twitches strong
29
fade: Total neuromuscular block
no fade
no twitches
30
what do nondepolarizers block?
presynaptic
and
postsynaptic
31
what do depolarizers block?
postsynaptic only
32
nondepolarizing block
less Ach released
fade observed
33
depolarizing block
equal Ach released
no fade released
overall twitch height decreased
34
what nerve patterns can show fade?
TOF
Tetanus
DBS
PTC
35
what nerve pattern cannot show fade?
single twitch
36
what frequency do you need to show fade?
>=2Hz
37
what does fade tell you?
how paralyzed the pt is
38
no fade means
pt is completely reversed
39
presence of fade means
pt is partially paralyzed
40
what is the gold std in assessment of recovery of neuromuscular blockade?
fade
41
is fade referring to onset or recovery or both?
recovery only
42
what nerve stim pattern can differentiate between depolarizing and nondepolarizing block?
TOF
Tetanus
PTC
DBS
43
what nerve stim pattern cannot differential between depolarizing and nondepolarizing?
single twitch
44
traditional nerve stimulators provide _______ data
qualitative
45
qualitative nerve stimulator
Max Output
Tetanus
max output: 70mA
tetanus: 100Hz
46
black electrode
negatively charged
depolarizes membrane
47
red electrode
positively charged
hyperpolarizes membrane
48
ulnar nerve electrode placement
red: proximal
black: distal
3-6cm apart
49
facial nerve electrode placement
red: forehead
black: zygomatic arch in front of ear
50
subthreshold stimulus
no motor units respondt
51
threshold stimulus
one motor unit responds
AKA initial threshold for stimulation (ITS)
52
submaximal stimuli
increasing number of motor units respond
53
maximal stimulus
all motor units respond
AKA pre-relaxant control response
54
supramaximal stimuli
all motor units respond
55
if you dont use enough current to stimulate the nerve....
you can produce a lower strength muscle contraction
weak twitches
56
what stimulus do we need to stimulate the nerve for maximum twitch height
supramaximal
57
what current usually stimulates maximum twitches?
40-60mA
58
single twitch stimulation indications
1. muscle relaxant onset
2. determine supramaximal stimulus current
3. post tetanic count
4. continuous nerve stim to decr PONV
59
can single twitch assess recovery of muscle paralysis?
NOPE
60
single twich disadvantage
does not produce fade during recovery
cannot assess NMB recovery
cannot destinguish depolarizing vs nondepolarizing
61
what will happen if you use single twitch to monitor muscle relaxant onset
twitches will gradually fade away
62
what percentage of receptors must be blocked for twitches to start to fade away when monitoring with single twitch?
75%
63
where do you place the PNS for PONV stimulation?
ulnar nerve (61% pts had PONV)
median nerve (45% pts had PONV)
use median nerve
64
what accupuncture site is located on the median nerve?
P6
65
what current should you stimulate for PONV
50mA on the median nerve through single twitch
66
what are you comparing if you use single twitch to assess recovery?
max twitch height at end of case == max twitch height prior to muscle relaxant
67
TOF can tell us
how profound the neuromuscular block is
68
0 twitches
>90% block
69
1 twitch
90% block
70
2 twitches
80% block
71
3 twitches
75% block
72
4 twitches
<75% block
73
TOF ratio
strength of the 4th twitch compared to the first twitch
74
higher TOF ratio
lower fade
stronger muscle function
75
what TOF ratio is indicative of residual neuromuscular blockade?
<0.9
76
TOF disadvantage
not as good at measuring "deep" levels of blockade
77
tetanus advantage
assesses deeper levels of blockade
78
sustained tetanus >5seconds indicates...
that the pts muscle paralysis has been adequately reversed
79
disadvantage of tetanus
pain
80
PTC
assesses deepest level of paralysis
81
lower number of Post tetanic twitches
longer wait for twitch return
15-20 mins
82
higher number of post tetanic twitches
shorter wait for twitch return
83
when can you reverse with neostigmine
PTC of 10+
or 2-3 muscle twitches
84
tetanus increases
total Ach in the synapse
larger contraction
85
double burst stimulation advantage
easier to see fade with naked eye
86
why do you wait between re-stimulating a nerve?
if you dont wait, it will produce a stronger muscle contraction
so you will underestimate the neuromuscular block
87
what pattern do you use for supramaximal stimulus?
single twitch
88
what pattern is good at assessing muscle relaxant onset?
sing twitch
89
what pattern is good at assessing partial blockade and recovery from blockade?
TOF
tetanus
PTC
DBS
90
what pattern differentiates between depolarizing and nondepolarizing?
TOF
tetanus
PTC
DBS
91
what patter can assess deep levels of blockade?
tetanus
PTC
DBS
92
time between TOF stimulations
10-30s
93
time between DBS stimulations
12-15s
94
time between tetanic stimulations
2 mins
95
time between PTC stimulations
6 mins
96
recovery of muscles order
1. diaphragm
2. rectus abdominus
3. laryngeal adductors
4. orbicularis oculi
5. adductor pollicis
97
which nerve site is the best for determining onset time for intubation?
facial nerve
(orbicularis oculi)
98
facial nerve approximates
laryngeal adductors
99
which nerve site gives best confidence that breathing muscles are recovered?
ulnar nerve
100
direct muscle stimulation is most likely on what nerve
facial nerve
101
alternate nerve monitoring site
posterior tibial nerve
102
neostigmine dosing: 4 twitches w/o fade
0-1 mg neostigmine
103
neostigmine dosing: 4 twitches w/fade
1-2 mg neostigmine
104
neostigmine dosing: 2-3 tiwtches
2-3 mg neostigmine
105
neostigmine dosing: 1-2 twitches
4-5 mg neostigmine
106
sugammadex dosing: 4/4 w or w/o fade
1mg/kg
107
sugammadex dosing: 2/4 or 3/4
2 mg/kg
108
sugammadex dosing: 1/4
3 mg/kg
109
sugammadex dosing: 0/4 w/1 twitch post tetanus
4 mg/kg
110
sugammadex dosing: 0/4 and no post tetanic twitch
wait
111
what dose of Roc is needed to re-paralyze the pt?
dose of sugammadex: <4mg/kg
>= 4 hrs ago
0.6mg/kg
112
what dose of Roc is needed to re-paralyze the pt?
sugammadex: 4 mg/kg
<= 5 mins
1.2 mg/kg
113
when do you have to wait 24 hrs after sugammadex to re-use Roc?
if 16 mg/kg dose was used
renal insufficiency/failure pts
114
what can you use instead of Roc to re-paralyze the pt?
Cisatracurium (nimbex)
115
indicators of adequate reversal
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
NIF
the greatest negative pressure a pt can generate during inspiration
117
what NIF means a pt is extubatable?
-20 to -30 cmH2O
118
what NIF indicates adequate reversal but no airway protection?
-25cmH2O
119
what NIF indicates adequate reversal w/airway protection?
-30 cmH2O
120
what is the most reliable indicator of adequate reversal
TOF ratio
121
TOF ratio >0.75
5 sec head lift
sustained tetanus >5 s
cough
NIF -25 cm/H2O
122
TOF ratio >0.9
pts can sit up unassisted
normal pharyngeal function
123
TOF ration <0.9
risk of aspiraiton
124
Physiologic factors that prolong duration of MR
hepatic disease
renal disease
hypothermia
increased age
MG
premature neonates
acidosis
125
electrolyte abnormablites that prolong duration of MR
hypocalcemia
hypercalcemia
hypomagnesemia
hypermagnesemia
hypokalemia
hypernatremia
126
meds that prolong duration of MR
aminoglycoside antibiotics (gentamicin)
inhalational agents
local anesthetics
ca channel blockers (verapamil)
antiarrythmics (diltiazem)
lithium (prolongs sux)
sux (prolongs NDMR)
127
phase II block
depolarizing block that resembles a nondepolarizing block
128
causes of phase II block
larger dose of sux (>6mg/kg)
sux redosing or infusion
129
how do you reverse a phase II block
neostigmine
or waiting
130
awake extubation advantages
less risk of obstruction
less risk of laryngospasm
protected airway
131
awake extubation disadvantages
coughing
bronchospasm
slow turn over time
132
awake extubation criteria
spotaneous ventilation
strong enough to breath
responds to commands
133
deep extubation
extubates when pt is spontaneously breathing but fairly anesthetized
134
deep extubation advantages
less likely to cough
faster OR turnover time
135
what surgeries might you want a deep extubation?
hernia
nasal septoplasty
tonsillectomy
136
deep extubation disadvantages
airway not protected
airway obstruction
laryngospasm
137
deep extubation absoluted contraidications
uncontrolled GERD
full stomach
hiatal hernia
difficult airway
airway edema
138
deep extubation criteria
sponteneously breathing
adequate tidal volumes
truly deep
thoroughly suctioned
139
deep extubation relative contraindications
obesity
OSA
140
