Neuromuscular blockers Flashcards
There are 2 types of nicotinic-R at the NMJ. What are they?
Prejunctional Nn receptor: on presynaptic n. (n = nerve)
Postsynaptic Nm receptor: at the motor end plate on the m. cell (m=muscle)
5 subunits of the postsynaptic nictonic-R. What are they?
alpha x 2
beta x 1
delta x 1
epsilon x 1
Extrajunctional-R come in 2 different forms. What are they?
1: 5 alpha subunits
2: gamma subunit replaces the epsilon
How much does K increase after Sch and for how long?
0.5-1.0
15 min
Do patients with upregulation of extrajunctional-R require more or less nondepolarizing relaxant?
MORE! More -R –> more drug required
Fade has to do with blockade of presynaptic or postsynaptic Ach-R?
PRE!
Ach is made up of what 2 things in the presence of what enzyme?
Choline
Acetyl coA
acetyltransferase
What role dose Ca++ play in Ach release?
Ca ++ entering the nerve terminal leads to Ach at the rim of the neuron being released
What role does Ach binding to prejunctional-R play in Ach being released?
Allows the stock pile to be moved down closer to the edge of the neuron
Do NDMB bind to presynaptic or postsynaptic neuron -R? What is the significance of that?
Presynaptic!
That means no more Ach can be mobilized down to be released, all that is available is what is sitting at the edge ready for immediate release.
Why do we see fade with NDMB but not Sch?
Fade is seen with Roc because NDMB bind to presynaptic Ach -R therefore not allowing mobilization of additional Ach down to the edge of the neuron for release. When the nerve is activated due to an action potential, Ach is released but with each subsequent twitches, there is less and less available Ach.
Does Sch work on the presynaptic or postsynaptic neuron?
Both!
Presynaptic: activates the Ach -R so that Ach continues to be mobilized and pushed down to the edge for immediate release (**This is why fade is not seen with TOF!)
Postsynaptic: activates the Ach -R to produce mibility but then it is unable to depolarize again until Sch is gone
What is a phase 1 block and does it happen with NDMB or Sch? Why?
When all twitches are equal even if diminished. There is no fade. Sch. Because there is plenty on Ach available in the presynaptic neuron that can be mobilized and released to bind to available Ach R
What is a fade 2 block?
Fade. Occurs with NDMB.
Recovery after muscular blockade should be measured where? Central or peripheral?
peripheral (because recovers late)
Which m. are more resistant to muscular blockade? (central or peripheral) Which recover quicker?
Central are more resistant
Central recover first
Do laryngeal muscles get blocked before or after diaphragm
before
Best place to test for onset of block (intubating condition)
What n. does it test
orbicularis oculi (eyelid)
corrugator supercilii (eyebrow)
Nerve = 7
Best place to measure recovery of nmblockade (return of upper airway m. function)
Adductor pollicis (thumb adduction)
Flexor hallucis (big toe flexion)
Ulnar n.
Post. tib. nerve
There is residual blockade after NMB drug is given if TOF ratio is less than _
0.9
What is the MOST accurate acceptable clinical test that can be done to determine neuromuscular function has returned?
Holding tongue blade in the mouth while you try to pull it out
What are 3 other tests that also indicate 50% of -R are occupied like with the tongue blade test?
head lift
hand squeeze
inspiratory better than -40
80% of -R are still blocked when you see what on your vent?
> 5 mL/kg Vt
Even with TOF no fade how many -R are still blocked
70
