PNS Stimulator Flashcards by Veronica Robinson

T/F
The Nerve stimulator is a comprehensive, all-encompassing assessment of muscle relaxation.

False
Highly subjective
prone to errors/misreading
its a tool, not the end all be all

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Feeling for twitches vs. watching

feeling for the twitch is a more accurate assessment

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What affects lead contact?

sweating
hair
edema/gross anasarca
wounds

anything that interferes with conduction of stimulating current

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Adductor Pollicis Muscle
innervation

innervated by ulnar nerve

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When stimulating the adductor pollicis muscle, we see…

thumb adduction/twitching

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Which muscle group is a good indicator that upper airway muscle fxn has recovered?

Adductor pollicis muscle

thumbs UP for UPPER airway

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Adductor pollicis muscles are sensitive to ___ and recovers (before/after) the diaphragm, laryngeal adductors and abd muscles.

NMB
after

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T/F
If our adductor pollicis muscle TOF is 0/4, this is a good indicator the pt is no longer breathing on their own.

False
Addctr pollcs could be zero, but patient could be breathing

the addctr pollcs recovers AFTER the diaphragm, laryngeal adductors and abd muscles.

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Adductor Pollicis muscle residual could indicate….

upper airway obstruction!

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Do we see twitches return faster in the face or in the ulnar region?

Face twitches disappear faster, but they return quicker (than ulnar region)

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Adductor pollicis lead placement

palm up, relaxed
leads are above ulnar nerve’s path
black/distal lead @ level of wrist on ulnar surface of flexor crease
second/proximal/red lead 1-2 cm more proximal; parallel to flexor carpi ulnaris tendon

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Which color is the distal lead?

black

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what color is the proximal lead?

red

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what locations are part of facial nerve stimulation?

orbicularis oculi

corrugator supercilli

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Orbicularis oculi
location
response

covers eyelid

NMB reponse similar to adductor pollicis (thumb)

eyelid squint

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corrugator supercilli
location
response

covers eyebrow

similar to laryngeal adductors, but faster onset and recovery

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What should we stimulate to assess good intubating conditions and profound blocks?

Eyebrows (corrugator supercilli)

(note: orbicularis oculi is better for intubation d/t its onset & recovery being more similar to the laryngeal muscles)

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Cautions when using corrugator supercilli/eyebrow for TOF

it recovers FASTER than the upper airway & addctr pollicis (airway may still be paralyzed!!!)

Full twitches here do NOT indicate full strength has returned

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T/F
4/4 twitches in the corrugator supercilli indicate full muscle strength has returned.

FALSE

cor.supercil recovers faster than the airway

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T/F
TOF assessment is imprecise and subjective.

true

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Facial Nerve lead placement

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T/F
The diaphragm is (more/less) resistant to blockade. It requires ___ the dose to paralyze than the ____.

more resistant
needs 2x dose of addctr pollcs

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T/F
a pt may have no twitches in thumb, but be breathing, coughing or moving their vocal cords.

True
diaphragm requires 2x the dose of paralytic to paralyze than the addctr polcs

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___ and ___ are less sensitive to blocks than the adductor pollicis.

Laryngeal muscles
diaphragm

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Which medication may alter the expected pattern of muscle recovery?

Succinylcholine

The face indicates when we can ___, but not when we can ___.

can indicate when to ETT doesn't indicate if we can ExTT face twitches return faster than spont. breathing (laryngeal/diaphragm); pt may be apneic even if TOF 4/4 on face

T/F Facial nerves paralyze faster but recover slower than peripheral nerves.

False central paralyzes and recovers faster (facial vs ulnar)

T/F Complete recovery at the corrugator supercilli indicates full recovery at the adductor pollicis.

False Can have full recovery of C.S. but incomplete recovery of A.P.

Posterior Tibial Nerve is good for which cases?

No access to face/arms trauma burns

Posterior Tibial nerve location response

Posterior Tibial Nerve is comparable to....

adductor pollicis (ulnar nerve/thumb)

Posterior tibial nerve lead placement

Peripheral nerve stimulator

stimulation of periph nerve and its response

Peripheral nerve stimulator delivers currents at...

0-70 miliamp (mA)

Peripheral nerve stimulator contains _________ to decrease resistance.

stimulating electrodes w/ silver-silver-chloride interface

P. Nerve stimulators use ____ current.

direct curent (DC) current goes to and from (instead of going in one direction)

What battery can we put in the PN stimulator?

9 volt

⭐️ T/F The PNS is a quantitative measuring tool.

False QUALitative

Why is the PNS assessment considered subjective and variable?

interpretation amongst providers

TOF assessment when giving succinylcholine

assess TOF after giving and before providing additional doses Pt may have unknown pseudocholinesterase deficiency & if twitches don't return, we won't know what caused it

Limitation of surface electrodes

don't always stimulate all nerve fibers may take several mins until optimal effect subject to resistance -aren't close to nerve -improper placement -obesity -hair

Which has greater ability to stimulate all nerves? surface electrodes needle electrodes

needle

How much current and frequency can we use to asses TOF without inducing muscle fatigue?

0.1 Hz once Q10 secs increase to brief tetanic stimulation, 50 Hz

___ Hz will cause sustained muscle contraction, known as ___. Fade will be (present/absent)

50 Hz tetanus no fade

Supramaximal PNS stimulation occurs at ___ Hz and causes...

>70 - 200 muscle fatigue/fade

What contributes to the presence of fade on TOF?

muscle fatigue (excessively high Hz and/or overly frequent TOF assessment)

T/F Increased frequency of stimulation can restrict blood flow to the area.

False dont spam the button

T/F We can stimulate the nerve as desired without it affecting our assessment of block depth.

False It can Again...don't spam the button

Five main patterns of stimulation

0.1 Hz means we stimulate every....

10 seconds

Which pattern of stimulation is least precise?

single twitch

Single twitch frequency range

0.1 Hz (1 stimulus every 10 secs) 1.0 Hz (1 stimulus per second)

Single twitch requirements

needs baseline comparison (perform before giving paralytic)

Can single twitch be used to determine recovery?

No determines onset of a block but not recovery

TOF ____ stimuli @ ___ Hz

4 repetitive stimuli at 2 Hz (2/sec)

⭐️ Even with TOF 4/4, ___ receptors may be still be ____.

75% blocked TOF is not very accurate!

Which type of NMB agent is associated with fade in TOF?

non-depolarizing

minimum TOF to determine extubation readiness

TOFr >0.9

T4/T1 definition

fade ratio size of fourth twitch/size of first

Fade ratio of 1.0 occurs when...

no muscle relaxant given

Fade ratio of 0 occurs when...

full muscle relaxation. (4/0 = 0; went from from 4 to 0; fully relax)

Can TOF detect a phase II block?

Yes!

Your patient's fade ratio is 0.5. What does this mean?

first 2 twitches are equal; 50% of twitches are equal considered partial block bottom example in picture

T/F TOF 3/4 twitches means the ratio is .75

No Twitch height determines ratio, however, we cannot determine this by naked eye.

What is the TOF ratio here?

0.40 or 40% T4/T1

What type of NMB?

nondepolarizing

What type of NMB?

depolarizing succinylcholine (phase I)

No twitches but diaphragm might move ___% blocked

___% blocked 1/4 TOF w/ relaxed abd muscles

TOF Pt can sustain head lift & hand grasp. What % blockage?

30 this does not guarantee pt won't fall back asleep and become apneic

Normal VC and TV are restored at ____% blockage.

70-75 accompanied by 4/4 TOF

T/F Fade is never exhibited with succinylcholine

False Depends on phase Phase II = fade

Tetanic (TET) Stimulation is a sensitive indicator to...

residual NMB

Tetanic (TET) Stimulation how does it work?

TET fades/fatigues at (full/partial/no) block.

partial

Posttetanic Count (PTC)

helps predict with TOF twitches will return 1) 5 second, 50 Hz tetanic stimulus 2) 3 second break 3) single twitch stimuli @ 1 Hz. “PTC predicts”

One of the best ways to use TET stimulation is...

in combination with TOF to assess for residual NMB TOF could be 4/4, but a fade on TET shows residual NMB

When should we use Posttet count (PTC)?

profound block with 0/4 TOF “Use PTC for Profound”

PTC Less twitches in the single-twitch portion means that...

longer time until TOF response returns (PTC: profound block; predicts TOF return TET: test for residual block)

PTC is used to guide ___ especially with ___.

reversal sugammadex

What effect does the tetanus of PTC cause?

-mobilizes Ach at prejunctional membrane -more is available at endplate to get PT (post-tetanic) twitches

Double Burst Stimulation (DBS)

Double burst stimulation (DBS) has a (greater/lesser) muscle response than TOF.

greater

In Double burst stimulation, fade is detected...

In partial blocks -second burst - if TOF ~0.6

What causes muscle fasciculations

-pre jxnal action of suxx -stimulating ACh receptor on motor nerves -repetitive firing -release NT

recovery of Phase I block

suxx diffuses away from NMJ metab by plasma cholinesterase

Phase II block is caused by...

prolonged exposure of suxx in NMJ (infusion, repeated dosing)

Phase I block twitches

4 equal twitches before giving and after administration

Depolarizing block is characterized by...

Decreased twitch tension no fade on tetanic or TOF(repeated stimulation) No post-tet potentiation

Phase I or II? Symmetrical decreased in size of all responses to TOF

Phase I

Phase I or II? No fade

Phase I

Phase I or II? T4/T1 ratio is 1.0 until ALL twitches disappear together

Phase I

Phase I or II? TOF acts like NDMR

Phase II

Phase I or II? Fade develops in response to TOF

Phase II

Phase I or II? results from too much/repeated depolarizer

Phase II

Which muscles face faster onset and recovery of blocks?

central muscles with good blood supply

Upper airway muscles & pharynx behave as (central/peripheral) muscles at onset. Their recovery is (fast/slow) d/t to their (sensitivity/resistance) to NMB drugs)

central slow recovery b/c they're sensitive to NMB drugs

**ideal** muscle to monitor during induction/intubation why?

-orbicularis oculi -more similar to central muscle onset similar to laryngeal/diaphragm muscles (note: the corrugator supercili is also good, but not *as* good b/c its onset & recovery is faster than the laryngeal muscles) | orbicularis is optimum for onset!

most valuable stimulation pattern at induction why?

TOF disappearance of TOF corresponds to optimal intubation conditions (use single twitch stimulation to allow max stimulation level)

T/F TOF 0/4 is needed for induction

False not necessary for induction but it is for surgical conditions

T/F Using the adductor policis for TOF during maintenance of anesthesia can indicate good diaphragm paralysis.

False Adductor policis may be 0/4 TOF, but the diaphragm may not be paralyzed. The diaphragm is resistant to blocks. The adductor policis is more sensitive.

Which site should be monitored during the maintenance of anesthesia?

orbicularis oculi reflects diaphragm more closely

Most useful measurements during profound NM block

PTC and TOF

TOF should be at least ___ before administering NM **antagonist**

1 or 2 more is better! d/t waiting times for reversal agents to start working

during reversal and recovery, which location should be monitored?

adductor policis (peripheral muscles) face recovers faster than diaphragm/laryngeal muscles

T/F Head lift is considered subjective monitoring.

True feeling and looking = subjective hard numbers = objective

Acceleromyography (AMG) mechanism

ulnar nerve measure acceleration of a muscle response --> ratio TOFR based

AMG requirements

thumb must be allowed to move (cannot tuck) susceptible to pt movement

drugs that can potentiate NMB action (7)

antiBx (aminoglycosides) **loop diuretics (furosemide)** mag sulfate lithium salts Ca Ch blockers **quinidine** procainamide | CALM People Love Questions

Besides drugs, what can potentiate NMB drugs?

hypothermia acid-base imbalance

If residual NMB is not recognized and we extubate, what could happen?

Evidence of inadequate NM recovery

T/F Sedatives should not be used when attempting to manage an extubation in the presence of residual NMB.

False sedatives are part of the management plan "you may have to sedate the pt as you try to wake them up" Dr Rogers

Management of extubation w/ residual NMB

**can use LMA if pt not full stomach

PNS Stimulator Flashcards

(114 cards)