Peripheral Nerve Stimulator Flashcards
nerve stimulator outline (6)
1-nerve electrically stimulated
2-ach released
3-ach binds nicotinic ach R
4- ach eventually degraded
5-prejunctional ach R allow choline and acetic acid to enter nerve again
6- choline and acetic acid form ach again
how long does each stimulus last?
0.2msec (200 microseconds)
Why wouldn’t you use stimulation durations of >500microseconds?
it would have the ability to cause direct muscle stimulation
when Ach binds to nicotinic R and the R arnt blocked what happens?
twitch occurs
when Ach binds to nicotinic R and the R are blocked what happens?
weaker twitch or no twitch occurs
what is Ach degraded into?
acetic acid and choline
what plays an important role in preventing the stockpiles of Ach inside the nerve from being depleted?
prejunctional Ach R
weak muscle contraction
some of the R are blocked by muscle relaxant
zero muscle contraction
100% of R are blocked
reversing muscle paralysis with neostigmine
muscle relaxants and Ach competitively bind
junction being flooded with Ach then Ach overcomes muscle relaxant
reveral with neostigmine and there is too much muscle relaxant on board
wont be able to overcome the muscle relaxant
need some muscle function before neostigmine
reversal with sugammadex
binding and encapsulates muscle relaxant and removes it from junction
can reverse deeper levels of relaxation
what are the 5 types of nerve stimulation patterns?
single twitch train of four tetanus post tetanic count double burst stimulation
pulse duration
0.2msec
200microseconds
what are the two types of single twitch nerve stimulation
1 Hz (1 stimuation per second) 0.1 Hz (1 stimulation per 10 seconds)
describe train of four nerve stimulation
delivers 4 stimuli (0.2msec each) over 2 second period (2Hz)
what is the amount of time between stimuli for train of four
500msec
if the person is unparalyzed what will TOF show?
four twitches
tetanus
continuous nerve stimulation at 50-100Hz
floods junction with max Ach
sustained muscle contraction
what is the time limit for tetanus?
5 seconds
very painful
post tetanic count (PTC)
50Hz tetanus for 5seconds
3 second pause
single twitch stimulation at 1Hz
Double burst stimulation (DBS)
two short tetanic stimulations separated by 750msec pause
first stimulation DBS
3 impulses at 50Hz
second stimulation DBS
2 options:
two impulses at 50Hz (DBS 3,2)
three impulses at 50Hz (DBS 3,3)
fade
ocurrs when nerve is stimulated multiple times in a row and partial blockade
1st twitch stronger than 2nd
2nd stronger than 3rd
etc
what does fade mean for the ach stockpiles?
less ach is released with subsequent twitch
stockpiles are more and more depleted
muscle contraction smaller
absence of fade
equal amounts of ach released from nerve on all twitches
fade and depolarizers vs nondepolarizers
fade will occur with nondepolarizing block
fade will NOT occur with depolarizing (phase I) block
where do nondepolarizing muscle relaxants block?
presynaptic and postsynaptic Ach R
partial nondepolarizing block with fade explained
presyn Ach R blocked
choline and acetic acid cannot get back in
stockpiles diminish
less ach available for repeated stimuli
how do the stockpiles of Ach get back to normal in partial nondepolarizing block?
nerve rest for short period of time
the greater the degree of muscle paralysis (from partial nondep block) means (4)
1-higher number of presyn R blocked
2- lower amount of ach released on back to back stimuli
3- higher degree of fade
4- longer the nerve will have to rest before stockpiles refill
where do depolarizing muscle relaxants block?
postsynaptic ach R
partial depolarizing (phase I) block
choline and acetic acid can rapidly reenter
stockpiles will NOT diminish
equal amounts of Ach available for repeated stimuli
no fade observed
Will the twitches in a partial depolarizing (phase I) block be even in back to back stimulation? what about will they be the same height (strength) as before the block?
even twitches for partial
the height will be diminished when comparing before block and during block
what are the two things needed in order for fade to occur?
partial nondepolarizing block
nerve stimulated at relatively high frequency
what is the gold standard of assessment of recovery of neuromuscular blockade?
fade
If the patients fourth twitch is as strong as the first twitch what does that mean?
the patient has for sure adequately recovered from neuromuscular blockade
during the onset of a partial nondepolarizing block what will you see?
twitch height gradually decrease or fade away (TOF and single twitch)
during onset of a partial depolarizing block what will you see?
twitch height gradually decrease or fade away (TOF and single twitch)
no fade with each individual train of four pattern
during recovery of partial nondepolarizing block what will you see?
fade with TOF but not single twitch stimulation (bc single isnt fast enough frequencies to deplete stockpiles)
