Lecture 4 Test 3 Flashcards
If you want to keep tabs on your paralytics and check how deep your NM block is, what can you do?
Neuromuscular monitoring (TOF)
How does neuromuscular monitoring work?
Place 2 electrodes on top of a nerve and when you run a current through these, it should cause a depolarization.
How can you generate an action potential externally?
TOF
What does it mean when you see a reaction after running a current through the ulnar nerve?
Your paralytic on board isn’t that deep.
What does it mean when you don’t see a reaction after running a current through the ulnar nerve?
Your block is deep
What does it mean when you see a minimal reaction after running a current through the ulnar nerve?
Your block may be wearing off.
What happens when you run a current of electrons outside of the cell.
Generate an action potential.
What does polarity mean?
There’s a charge difference between inside and outside the cell.
If there’s no difference between the charges inside and outside of a cell, this mean….
It is depolarized!
Are EKG’s looking at the current inside or outside of the heart cells?
Outside of the heart cells
What is the required voltage needed to dial in for your neuromuscular monitoring called?
Supramaximal stimuli
Term for “strong enough to recruit all the motor neurons in the underlying nerve”.
Supramaximal stimuli
TOF setting
2Hz / 2 secs = 2 impulses/1 sec = 4 impulses / 2 secs
How can you tell if you’re using a non depolarizing block based on the TOF?
The first twitch is stronger and gets weaker each time.
How can you tell if you’re using a Depolarizing neuromuscular blocker?
Equal strength on all 4 twitches.
What is Tetanic contractions?
High frequency stimulation for a short period of time. More than 4 impulses.
Causing continuous depolarizations for a period of time.
Unable to fully relax between depolarizations.
Checking for impulses the muscle generates after High frequency impulses to see the health of the synapse
Post tetanic count
What is double burst stimulation?
High frequency stimulation for a couple of secs, lay off and then do it again. In order to check for different characteristics of the neuromuscular block.
What happens when the ulnar nerve is stimulated?
Thumb comes forward and pinky twitches.
What does the ulnar nerve innervate when stimulated?
Adductor pollicis muscle
What other sites for TOF
Facial nerve
Peroneal nerve
Posterior tibial nerve
Which blocking agent takes into effect faster? NDMR or DMR
DMR (Succs)
What’s another reason why Succs is good to use?
It’s fast onset, short acting and it’s cheap! per Dr. Schmidt
Based on NDMR meds, how does your twitches return as the meds wear off?
You get one twitch at a time, first being stronger and the others get weaker and weaker until all 4 twitches are equal.
B/A is closer to 1 = recovered
As the drugs wear off for an NDMR agent how do you measure the ratio of each twitch?
The first twitch is labeled as A and the 4th twitch is B. Initially, the B over A ratio is very small. As the drug wears off, the ratio gets closer to 1.
Why’s is the first twitch of the TOF always stronger in a NDMR?
The first twitch has enough ACh to release on the first depolarization while the next subsequent depolarizations have lesser and lesser ACh being released from the neuron.
What’s the difference between the B over A ratio of a DMR block vs NDMR?
DMR: It is always closer to 1 since the A and B twitches are the same.
NDMR: Has a B/A ratio that’s less than 1 and it gets closer to 1 the closer the meds wear off.
What is the target of an NDMR?
Motor neuron and skeletal muscle.
What does an a3 b2 receptor do?
3 places to bind ACh, and 2 beta subunits. ACh is released and binds to the skeletal muscle and the others bind back to the ACh auto receptor to help complete with VP1 to VP2.
When NDMR binds to the skeletal muscle receptor and also bind to the auto receptor (a3b2) it will prevent VP1 from becoming VP2…..
leads to a weaker subsequent contraction.
Why’s does each contraction get weaker during each TOF when NDMR is used?
The first twitch had more time to figure out how to replace VP2 and have fewer storage vesicles available for the other twitches.
Effects of DMR on TOF.
DMR affects the skeletal muscle to be constantly depolarized and no effect on the presynaptic neuron so VP1 and VP2 aren’t affected. Once the drug wears off, there’s a constant supply of VP2 for each twitch.
How is succs broken down?
Plasmacholinesterase from the liver.
Do autoreceptors have gates?
No, it opens when an ion binds to it.
Are there L type calcium channels in the presynaptic cell?
Yes
Does the CCBs work on L type channels in the presynaptic cell?
No
T/F : If you’re hungover and shaky the L type ca channel can help settle it down.
True
What happens when you give succs to a stroke Pt?
Prolonged depolarizations due to Fetal n-ACh-R causing increased surface area and hyperkalemia in the ECF.
Less important muscle i.e. Adductor Pollicis muscle req. 40mcg/kg to be paralyzed.
Diaphragm (more important skeletal muscle) starts at 40mcg up to 90mcg/kg to be paralyzed.
Less important muscles requires less meds to be paralyzed.
The more important muscles require more drugs to block d/t more receptors.
Which spinal nerves control the diaphragm???
Spinal nerves C3, C4, C5 (Phrenic nerve)!!!!!!!!!!!!!
Can you still breathe if you have a complete lesion at T1
Yes
As the block wears off, which will recover first? Diaphragm or adductor pollicis?
Diaphragm
How do you know if the patient is going to be able to breathe on their own?
Diaphragm recovers faster than the adductor pollicis.
If the adductor pollicis has 4 strong twitches. Diaphragm has completely recovered way before the twitches occur.
What does it mean if you have 3 of 4 TOF?
75%-80% nACh-R blocked
What does it mean if you have 2 of 4 twitches?
85% nACh-R blocked
What does it mean if you have 1 of 4 twitches?
85% - 90% nACh-R blocked
How many % of nACh-r blocked if the Pt can lift their head?
70% and all 4 twitches should be present as well.
What does it mean if all twitches are gone?
90% - 95% nACh blocked
How many mA is the Stimulator settings?
50-80 mA
The ocular system has several motor neurons and if paralyzed with a depolarizing muscle block it can…..
cause ca++ influx, increase IOP. risk for vision loss
What is GABA used for?
Limit neural activity
Inhibitory neurotransmitter in the spinal cord
Glycine
What are the 2 inhibitory neurotransmitter in the spinal cord?
Gaba and Glycine
What else is acetylcholine used for?
Makes us more awake/aware in the brain
Increase CNS; neuronal activity
What happened when ACh is blocked in the CNS?
drowsiness (anticholinergic)
ex. m-ACh-R antagonist
Benadryl (Anticholinergic, antihistamine)
What can you give someone with Alzheimer’s to be more aware?
To increase ACh (inhibit AChesterase), give stigmines = more awareness/active
If you give AChesterase inhibitor, one side effect could be
Bradycardia d/t m-Ach-R in the heart.
If you don’t want to wake someone up but want to reverse a paralytic…
Might want to give an AChesterase that doesn’t cross the BBB
What else can cause a similar affect on CNS like ACh?
Histamine
Ex. of Stimulatory CNS neurotransmitter that’s also involved with pain sensors
Glutamate
Potent motor inhibitor
Dopamine
Disease with low dopamine = overactive motor system
Parkinson’s Disease
5 ex. that increase awareness in CNS
Norepi
ACh
Dopamine
Glutamate
Histamine
Acid base balance and CNS activity
(acidosis) low pH = low CNS activity
(alkalosis) high pH = increase CNS activity but decrease cerebral blood flow! (Co2 increases cerebral blood flow!)
Body buffers acids in the blood with bicarb to cause CO2 and water release
H+ (+) HCO3- = H2CO3 = CO2 (+) H2O
Hypoventilation (acidosis) Albumin in the blood binds to more protons H+ causing…
increase free Ca++ reduce CNS activity
Hyperventilation (alkalosis). Albumin in the blood binds to more Ca++ causing…
decrease Ca++ in ECF > ICF is more + > increase CNS activity.
*Increase neuronal activity; decreased oxygenation to the brain d/t co2 causing increased cerebral blood flow.
