Exam 5 NMB Flashcards
depolarizing muscle relaxant
succinylcholine
Succinylcholine MOA
mimics action of ACH by binding to the motor endplate
Phase I block
SUCC
motor endplate closes and cannot reopen until depolarization (can’t happen when depolarizer is bound)
Succincholine is an
ACH receptor agonist
plasma cholinesterase aka
pseudocholinesterase
butylcholinesterase
Succinylcholine unique abilities
fast onset (34 seconds)
short duration (2-4) min
Non-depolarizers are
ACH competitive receptor antagonists
Non-depolarizer MOA
Compete with ACH for motor end plate - bind but do NOT cause conformational change
Reversal of non-depolarizing muscle relaxants concept
whoever has more at synaptic cleft wins
More Ach: conformational change
More non-depolarizing agent: no conformational change = no contraction
Non-depolarizer REVERSALagents are
cholinesterase inhibitors
allows for accumulation of Ach to win battle of who has more wins
Suggammadex MOA and which drugs it works on
selectively binds to NMBD
drugs: rocuronium, vecuronium, pancuronium
Sugammadex considerations
birth control interference - 7 days
Peripheral nerve stimulation indications
used to monitor degree of NMB:
1. assess conditions for endotracheal intubation
2.. asses if degree of block is sufficient for surgery
3. Monitor recover from block and successful extubation
Single twitch (use and energy)
0.1 to 1.0 Hz
compare to baseline twitch before drug administration
Train of four (use, energy, timing)
want ratio of 0.9 (4th twitch is at least 90% of 1st twitch)
four equal 2.0 hz 0.5 sec apart
Double burst stimulation (energy, timing, use)
two short bursts of 50 hx tetanus separated by 0.75 seconds
Similar to train of 4 (may be easier to detect)
Tetanus (energy, timing, use)
rapid 30-50 or 100 Hz for 5 seconds
deep block assessment - painful, use sparingly
Postetanic count (energy, timing, use)
50 Hz for 5 sec, 3 sec pause, single twitches of 1 Hz
used when TO4 is absent, deep block, or prolonged recovery likely
With neuromuscular blockade, what will you see with different twitch stimulation?
Single twitch: Less movement (cannot clinically give much info. need baseline twitch)
TO4: fade
Tetanus: decreased contraction over duration
Post tetanic twitch: fade
Double burst: fade
TO4 use
distinguishes between depolarizing and non-depolarizing blocks
*useful in determining recovery from NONDEPOLARIZING muscle relaxants
wiht TO4, 4 twitches can still be ____% blcoked
70%
with TO4, we want to avoid _____ twitches because ____
avoid 0 twitches because this is a 95% + block, and if we 100% block, we cant reverse fully (residual paralysis)
Most common method in assessing clinical response to NMBs
TO4
It is difficult to detect (visually or tactile) fade when TOF ration exceeds
0.4
need objective quantitative assessment when TO4 exceeds 0.4
Clinical recover form NMB is achieved when TOF ratio is
0.9
Reversal agent is indicated when TOF ration is
<0.9
absence of fade:
does NOT guarantee adequate NMB recovery
can still have residual weakness
Tetanus indication for depolarizing block:
response is depressed in amplitude but is sustained (no fade)
*unless phase 2 block
Tetanus indication for nondepolarizing block
Response is depressed and NOT sustained (fade)
Tetanus assessment with TO4 assessment
TO4 may not be accurate for up to 6 min following tetanus assessment
Posttettanic count block indication
less than 8 twitches = deep block
posttetanic count MOA
mobilizes excess of ACH so that after 3 second pause you can produce a short series of single twitch responses
Posttetanic count of 6-8 means
reversal should occur in less than 10 minp
postetanic count of 1-2 means
reversal will take more than 50 min
Post tetanic count assesses
depth of NMB when no twitches are present in deep block
With no fade during double burst stimulation:
MAY be recovered, but could be up to 70% blocked still
Peripheral nerve stimulation monitoirng sites
- ulnar nerve (thumb adduction)
- facial nerve
- posterior tibial nerve
Order of relaxation with NMB
eyes–>extremities–>trunk (neck then down)–abdominal–>diaphragm
*reversal is opposite
Regions of higher blood flow have
faster onset and faster recovery
diaphragm–>masseter–>laryngeal muscles–>orbicularis oculi
Presence of spontaneous ventilation
NOT a sign of adequate neuromuscular recovery
Diaphragm recover vs upper airway muscle recover
diaphragm recovers much faster than upper airway muscle (i.e. genihyoid)
genihyoid muscle relaxes at same time as
adductor pilus (thumb in TO4)
What nerve is more helpful in determining ONSETof block
facial nerve
What nerve is more helpful in determining strength or fuller RECOVER
ulnar nerve
with adequate TV, a pt can still be (% blocked)
80% blocked
(not adequate for extubation)
with no TO4 fade, a patient can still be (% blcoked)
70-75% blocked
(not adequate for extubation)
with adequate VC, pt can still be (% blcoked)
70%
(not adequate for extubation)
With no tetany fade, pt can still be (% blocked)
70% blocked
(not adequate for extubation)
with adequate inspiratory pressure, pt can still be (% blocked)
50% blocked
(usually adequate for extubation)
strong hand grip for 5 seconds pt can still be (% blocked)
50% (usually adequate for extubation)
5 second head lift, patient can still be
50% blocked
(gold standard for extubation)
The gold standard for extubation is
5 second head left
if a paitnetcan hold tounge blade in mouth angainst force, they can still be
50% blcoked
