Nagelhout Video 1 - Exam 1 Flashcards
Ultra-short neuromuscular depolarizing relaxants
Succinylcholine
Intermediate neuromuscular non-depolarizing relaxants
Vecuronium (Norcuron)
Cis-astracurium (Nimbex)
Atracurium (Tracrium)
Rocuronium (Zemuron)
Long acting non-depolarizing neuromuscular relaxants
pancuronium
Why is succyinylcholine considered depolarizing?
Because it is (essentially) Acetylcholine - it causes the muscle to contract or depolarize once
There is a period of paralysis while waiting for Succs to leave the synapse.
How do non-depolarizing neuromuscular agents work?
Like classic antagonists- they do not cause muscle contraction
What percent of muscle receptors is required for patient to have normal tidal volume / RR?
What are the implications of this?
20% of receptors
-pt could be 80% paralyzed, poor airway reflexes but have normal respirations
-this is why it’s important to know how many receptors are still occupied by a neuromuscular relaxant before extubating
You can’t be more than 100% paralyzed - what are the implications of this?
the more relaxant you give, the harder to get rid of the drug at the end of the case - the less relaxant you use the easier reversal will be
What type of muscle do neuromuscular relaxants work on?
Skeletal muscle only not cardiac or smooth muscle
What OR procedures require patient to be paralyzed?
Abdominal or chest procedures
When you give a neuromuscular blockade will this work on the bowel?
No because it is smooth muscle - but it will work on sphincter causing them to open up
*Which makes a patient susceptible to aspiration
Single Twitch test
single supramaximal electrical stimulus ranging from 0.1-1.0 Hz
Which Nerve stimulation test provides the least amount of information?
Single-twitch
What does the single twitch test require and what type of information does it represent?
requires a baseline assessment
QUALITATIVE not quantitative
- If they move they’re not paralyzed
- IF they don’t they are
Which Nerve stimulation test is the most popular?
Train-of-four
Train of Four (TOF)
-timing
-results
A series of 4 twitches at 2 Hz. every half-second for 2 seconds
Train-of-four ratio is determined by comparing T1-T4 (looking for fade)
Reflects blockade from 70-100%
Double burst stimulation
two bursts of 50 hz tetanus separated by 0.75 seconds
Compare the first and second twitch - look for fade (fade may be easier to detect than TOF)
Tactile evaluation
Tetanus
-energy used, process of
Rapid delivery of a 30, 50, or 100- Hz.
Stimulus for 5 seconds.
Should be used sparingly for deep block assessment - painful
Post- tetanic count
-Energy used and process
50-Hz. tetanus for 5 seconds, a 3-second pause, then single twitches of 1 Hz.
Tetantic should only be used when which two tests are absent?
Used only when TO4 or double-burst stimulation response is absent;
Tetanic: less than 8 indicates
<8 indicates a deep block and likely prolonged recovery.
Onset
time from drug administration to maximum effect
Clinical Duration of NMBD is usually
time from drug administration to 25% recovery of the twitch response
-DOA of a NMBD = time of recovery of 1/4 TOF twitches
Recovery index
Time from 25% to 75% recovery of the twitch response
Total Duration
Time from drug administration to 90% recovery of the twitch response
*This is the number we use to determine recovery time!
Train of Four Ratio (TOFR)
Compares the 4th twitch of a TOF with the 1st twitch.
When the 4th twitch is 90% of the first, recovery is indicated
Electricity flows from positive to negative, so it flows from what color electrode to what color electrode?
Flows from the red electrode to the black electrode.
Red electrode should be closest to…
the body (proximal)
The black lead should be closest to..
the twitch site (distal)
Think red goes closest to heart
Ulnar nerve
electrodes just above posterior wrist, pinky side.
*Goal is thumb adduction.
Which is the best site to monitor recovery?
ulnar nerve
Tibial, deep peroneal, and posterior tibial nerves
electrodes over posterior tibial nerve or behind knee
Facial nerve- electrode placement
front of the tragus of the ear and below and slightly posterior
-avoids direct stimulation of either the orbicularis oculi and frontalis muscles.
Best site to measure onset
facial nerve
Goal of facial nerve stimulation
eyelid movement
Facial nerve stimulation is the most relevant in
RSI
When stimulating the facial nerve - why do you not put the electrodes near the eyelid?
because then you are sending the electricity directly into the muscle, and it will contract (even if the patient is 100% paralyzed).
You are not actually paralyzing the muscle, but rather the nerve-to-muscle connection. With enough stimulation, the muscle can still depolarize.
The orbicularis oculi response to facial nerve stimulation reflects the extent of neuromuscular blockade of the_________________ better than does the response of the adductor pollicis to ulnar nerve stimulation
why is this?
Diaphragm
this is because the facial nerve receives similar blood flow/cardiac output to the diaphragm.
Which muscles are more sensitive to the nerve stimulation tests: upper airway or peripheral muscles?
upper airway muscles
T/F: · No difference in sensitivity exists between the arm (adductor pollicis muscle) and the leg (flexor hallicus brevis) muscles
True
Placement of electrodes when using temporal branch of the facial nerve-
Negative electrode should be placed over the nerve, and the positive electrode should be somewhere else on the forehead.
Neuromuscular relaxant sequence
- Eyelids - this is different than the facial muscles.
- Extremities
- Chest- intercostals - from strap muscles in neck and downward
- Abdominal muscles
- Diaphragm: hardest muscle in the body to paralyze!
**The muscles regain function in the opposite order!
What is the minimal current output that a peripheral nerve stimulator should provide?
30 mA
What type of neuromuscular function monitoring do we WANT to use when possible?
Quantitative
Tactile evaluation of TOF / DBS fade reduces but DOES NOT eliminate ______________________
post-op residual paralysis compared with the use of clinical criteria to assess readiness for tracheal extubation.
What should be established before pharmacologic antagonism of NMBD block with anticholinesterases - does not apply to sugammdex?
adequate spontaneous recovery.
T/F: Protective reflex muscles of the pharynx and upper esophagus recover later than the diaphragm, larynx, hands, or face.
True
Monitoring of the offset and recovery from neuromuscular blockade is probably better
at the ulnar nerve
Monitoring of which nerve for determination of onset and readiness for intubation may be preferable to monitoring of the ulnar nerve
Facial
When there is only one response to TOF stimulation, successful reversal may take as long as _____ minutes.
30
At a TOF count of two or three responses, recovery usually takes _________ minutes after intermediate-acting drugs and may take up to ______ minutes after administration of the long-acting relaxant Pancuronium
4- 15 minutes
30 minutes
When the fourth response to TOF stimulation appears, adequate recovery can be achieved within ____ minutes of reversal with neostigmine or 2 to 3 minutes after use of edrophonium.
5 minutes
The timing of tracheal extubation should be guided by monitoring tests such as
TOF >0.9
or
DBS3, 3 >0.9.
1 response TOF
90-95% blockade
**This is the ideal place to carry a patient in the OR!
2 responses TOF
80 - 85% blockade
0 response TOF
100% blockade (TOFR < .9 or 90%)
3 responses TOF
75%-80%
4 responses TOF
70 - 75% blockade (TOFR > .9 or 90%)
Does fade occur in non-depolarizing or depolarizing agents?
non-depolarizing because they affect both post-synaptic ACh receptors as well as the positive feed back loop of ACh at the pre-synaptic receptors
Is there fade with succinylcholine?
No because succinylcholine does not affect pre-synaptic ACh receptors only post-synaptic ACh receptors
TOFR becomes meaningless because 4:1 is always 100%
Normal response - tetanus contraction
Normal means you push the button and the hand should contract for 5 seconds (i.e. sustained contraction). If you get no response, you have 100% paralysis.
How to initiate a PTC
Apply tetanus at 50 Hz for 5 seconds Pause (wait) for 3 seconds
Apply single twitches every second up to 20
A PTC of “1” means that the time of the appearance of T4 in a TOF will be about
30 minutes for a Pancuronium and
8 minutes for either atracurium or vecuronium.
PTC = 10 was found to correlate with
appearance of the T, in the TOF.
Benefits of PTC
- It is helpful in assessing the level of blockade
- It is helpful in determining when and with what agent to reverse NM blockade.
Train of four tells us how paralyzed a patient is between
70-100%
Single twitch is all or nothing! Patient is either
- 100% or 0% paralyzed.
Tetanus is the strongest. If there is fade, patient is still
paralyzed
If all else fails, we can use the PTC. The lower the number
the more paralyzed the patient is. If PTC=2, call for a ventilator in the PACU!
Characteristics of depolarizing (phase I) blockade
Muscle fasciculation PRECEDES paralysis
sustained response to tetantic stimulation
No post-tetantic potentiation
No fade in TOF / DBS
Antagonized by pre-treatment with non-depolarizing agent (requires 20% more succinylcholine)
Potentiated by anticholinesterase drug
Characteristics of depolarizing (phase 2) blockade
No muscle fasciculation
Tetantic fade
Post-tetanic potentiation, stimulation, or fasciculation.
TOF and double-burst fade
Rare cases- may be produced by an overdose and desensitization with succinylcholine >6mg/kg
Reversal with anticholinesterase drug
