NMBD's Flashcards
True or False: Nicotinic receptors are located only on the post-synaptic end-plate.
False, located both pre and post synaptic.
Where are acetylcholinesterase molecules found?
Around post synaptic nicotinic receptors and in the synaptic cleft
Acetylcholine is synthesized from _____ and ____ through the action of _____
AcetylCoA and Choline, Choline Acetyltransferase (ChAT)
Release of Ach depends on the entry of ____ in to the terminal
Calcium
What does Calcium do once inside the nerve terminal?
causes vesicles to fuse with nerve cell membrane and exocytosis of Ach
What happens when Ach binds to a pre-synaptic nicotinic Ach receptor?
A positive feedback loop-it increases synthesis and release of Ach.
____ number of molecules of Ach must combine with 2 ____ subunits on the nicotinic receptor.
2, alpha
When both nicotinic subunits are occupied by Ach, the channels snap open and __ and ____ flow into the cell and ____ flows out.
Na and Ca flow into, K flows out
Acetylcholinesterase splits Ach into ___ and ____
acetate and choline
____ is transported back to the pre-synaptic terminal where it’s reconverted to Ach. ____ diffuses away.
Choline, acetate
What are extrajunctional nicotinic receptors?
Proliferate in response to paralysis, dystrophies, upper/lower motor neuron injury, major burns.
What happens as a result of extrajunctional nicotinic receptors?
Channels stay open 4x longer and upregulate-causes hyperkalemia
What are the subunits of a nicotinic receptor?
2 alpha, 1 beta, 1 delta, 1 epsilon
Depolarizing muscle relaxants act as acetylcholine receptor ______
Agonists
Non-depolarizing muscle relaxants act as ____ ____
competitive antagonists
Which medication is a depolarizing muscle relaxant?
Succinylcholine
Which medication is a long acting non-depolarizing muscle relaxant?
Pancuronium
Which medications are intermediate acting non-depolarizing muscle relaxants? (4)
Atracurium, Cisatracurium, rocuronium, vecuronium
Which medication is a short acting non-depolarizing muscle relaxant?
Mivacurium
What is the mechanism of action for Succinylcholine?
It mimics Ach. It works on the pre-synaptic receptors to mobilize ach and works at post synaptic receptors to open channels-Na/Ca enters the cell, K leaves the cell. This creates a prolonged depolarization.
What is the absolute refractory period?
action potentials cannot be initiated in the skeletal muscle until it REpolarizes. Voltage gated sodium channels in the membrane adjacent to the post synaptic terminal (motor end plate) snap in to the inactivated state.
What is the following for Succinylcholine? Dose: Onset: Duration: What is it broken down by?
0.5-1mg/kg
30sec
3-5 min
Plasma Cholinesterase (aka pseudocholinesterase or butyrocholinesterase)
What is the metabolite of succinylcholine?
Succinylmonocholine
What percent of succinylcholine actually reaches the neuromuscular junction? or What percent isn’t metabolized?
10%
What is the name of the enzyme that breaks down succinylcholine?
Pseudocholinesterase (aka plasma cholinesterase, butyrocholinesterase)
What are some example of situations that will have a prolonged blockage by succinylcholine?
Atypical plasma cholinesterase, severe liver disease, use of anticholinesterase medications
What are some drugs that lower plasma cholinesterase, which would prolong the effect of succinylcholine?
Metaclopramide Esmolol Neostigmine & Pyridostigmine Echothiophate Oral contraceptives/estrogen Cyclophosphamide MAOI's N2 Mustard
What are some conditions that lower plasma cholinesterase?
Atypical Anticholinesterase Severe Liver disease Chronic kidney disease burns advanced age Organophosphate poisoning neoplasm malnutrition late pregnancy
What does a dibucaine number tell you?
reflects the percentage of plasma cholinesterase that is inhibited when dibucaine is given. It has NO effect on atypical plasma cholinesterase.
Does a dibucaine number tell you the quantity or quality of the plasma cholinesterase enzyme?
Quality
About how long does it take to recover is your dibucaine number is above 80? 40-60? 20 and below?
above 80: 5-10 min. normal response
40-60: 20-30 min
20 and below: 4-8hr
What is a way to minimize fasciculations that may cause myalgias?
Give 1/10 of the ED 95 dose of a non-depolarizing muscle relaxant. (Ex. Roc, vec.) 3-5 min before giving succinylcholine
What are side effects of succinylcholine?
Bradycardia Tachycardia Hypertension Hyperkalemia Myalgias Myo-globinuria Increased intra gastric pressure Increased intracranial pressure Increased intraocular pressure Malignant Hyperthermia Masseter Spasm Prolonged respiratory paralysis (with atypical plasma cholinesterase)
Which receptors are being stimulated if succinylcholine causes bradycardia?
Muscarinic receptors
Which receptors are being stimulated in succinylcholine causes tachycardia and hypertension?
Autonomic ganglia nicotinic receptors
What are factor that prolong the depolarizing block of succinylcholine?
Antibiotics (especially aminoglycosides) local anesthetics Anticholinesterase agents (increases Ach Hyperkalemia Hypermagnesemia Inherited pseudo-cholinesterase effect Lithium
What are potential conditions that accentuate succinylcholine -induced hyperkalemia?
Undiagnosed muscular dystrophy burn (7-10 days post acute burn) Severe abdominal infections Severe metabolic acidosis Conditions with up-regulation of extra-junctional acetylcholine receptors (para/hemipalegia, muscular dystophies, gullain-barre, upper motor neuron lesions/injuries, CVA, etc)
What are the subunits on an extra-junctional nicotinic receptor?
7 alpha subunits and a gamma subunit (instead of an epsilon)
What is the mechanism of action for non-depolarizing muscle relaxants at the pre-synaptic area?
Inhibits mobilization of acetylcholine to be ready for exocytosis. This causes FADE
What is the mechanism of action for non-depolarizing muscle relaxants at the post-synaptic area?
Binds to Ach receptors, competitively blocking Ach from attaching. Channels stay CLOSED, no electrolyte influx/eflux. No depolarization of the muscle.
Are non-depolarizing muscle relaxants hydrophilic or lipophilic?
Hydrophilic
Are non-depolarizing muscle relaxants ionized or non-ionized?
ionized
T or F? Non-depolarizing muscle relaxants cross the blood brain barrier and can cross the placenta.
False
How are non-depolarizing muscle relaxants excreted?
Renal and liver
What are the two classes of non-depolarizing muscle relaxants?
Steroidal and Benzylisoquinolinium
What are the 3 non-depolarizing muscle relaxants classified as steroidal?
Pancuronium, Vecuronium, Rocuronium
Of the following, which are short, intermediate, and long acting?
Pancuronium (long), Vec & Roc (intermed)
What are the 3 non-depolarizing muscle relaxants classified as benzylisoquinolinium?
Atracurium, Cisatricurium, Mivacurium
Of the following, which are short, intermediate, and long acting?
Atracurium (Intermed), Cisatricurium (intermed), Mivacurium (short)
How are atracurium and cisatricurium metabolized?
Atracurium: 66% ester hydrolysis, 33% Hoffman
Cisatricurium: 77% Hoffman, no ester hydrolysis
Which category of non-depolarizing muscle relaxants is dependent on hepatic/renal function for elimination?
Aminosteroids
Where are benzylinsoquinoliniums metabolized?
by enzymes in the plasma
What is the metabolite of atracurium?
Laudanosine
With what condition should you not give atracurium to a patient? Why?
Hx of seizures because of laudanosine.
Which steroid non-depolarizing muscle relaxant should not be given with liver disease? What percent is eliminated by the liver?
Rocuronium, >70%
Which steroid non-depolarizing muscle relaxant should not be given with renal disease? What percent is eliminated by the kidneys?
Pancuronium, 85%
What percent of vecuronium in metabolized by which organ?
30-40% by the liver
Which non-depolarizing muscle relaxants have the primary route of elimination of metabolism?
Succinylcholine, atracurium, cisatricurium
Which non-depolarizing muscle relaxants have the primary route of elimination of the liver?
Vecuronium, Rocuronium
Which non-depolarizing muscle relaxant has the primary route of elimination of the kidneys?
Pancuronium
Which non-depolarizing muscle relaxant releases histamine?
Atracurium
Which two non-depolarizing muscle relaxants are metabolized by ester hydrolysis and Hoffman elimination, thus not affected by kidney or liver impairment?
Atracurium (ester) and Cisatracurium (Hoffman)
Which two non-depolarizing muscle relaxant rely on biliary excretion?
Roc and Vec
Which non-depolarizing muscle relaxant is excreted by the kidneys?
Pancuronium
Which non-depolarizing muscle relaxant has the most affect on the vagal blockade? Which one has an affect but not as strong?
Pancuronium, Rocuronium
If Hoffman elimination:
Alkalosis and hyperthermia=
Acidosis and hypothermia=
faster metabolism, shorter duration of action
slower metabolism, longer duration of action
What are the side effects of the histamine release from atracurium?
hypotension, tachycardia
Which non-depolarizing muscle relaxant is most associated with tachycardia?
Pancuronium (vagal blockade)
Which non-depolarizing muscle relaxant is most associated with anaphylaxis?
Succinylchloline
Which two non-depolarizing muscle relaxant release histamine?
succ and atracurium
Which paralytic would you avoid in a patient with idiopathic hypertrophic sub-aortic stenosis? Why?
Pancuronium. The tachycardia can cause the leaflet to block the left ventricular outflow tract, thus decreasing cardiac output and blood pressure.
Your patient is undergoing a stone extraction with a urinary stent and has Stage 3 kidney disease. Which paralytic would you use?
Cisatricurium. Both benzlisoquinoliniums do not rely on liver or kidney elimination, they are metabolized by ester hydrolysis and hoffman elimination. Cisatricurium is 16% renal elimination, atracurium is 10-40%.
What is the following for Pancuronium? Dose: -Intubating dose: -Maintenance dose: Onset: Duration: Metabolite: Elimination:
-Intubating dose: 0.1mg/kg
-Maintenance dose: .01 mg/kg
Onset: 3-5 min
Duration: 45-90 min
Metabolite: 3-OH
Elimination: 85% kidneys
What is the following for Vecuronium? Dose: -Intubating dose: -Maintenance dose: Onset: Duration: Metabolite: Elimination:
-Intubating dose: 0.1mg/kg
-Maintenance dose: 0.01mg/kg
Onset: <3 min
Duration: 25-30 min
Metabolite: 3-OH
Elimination: liver 50-60%
What is the following for Rocuronium? Dose: -Intubating dose: -Maintenance dose: Onset: Duration: Metabolite: Elimination:
-Intubating dose: 1mg/kg
-Maintenance dose: .1 mg/kg
Onset: 45-90 sec
Duration: 15-30 min (dose dependent)
Metabolite: ??
Elimination: liver 70%
What is an alternative paralytic to use for RSI instead of succinylcholine?
Rocuronium but longer duration of action (15-30 min)
What does it mean by a “priming dose”?
Give 10% of of the total dose, give induction med, then remaining 90% of the dose
What is the following for Atracurium? Dose: -Intubating dose: -Maintenance dose: Onset: Duration: Metabolite: Elimination:
-Intubating dose: .5mg/kg
-Maintenance dose: .1mg/kg
Onset: <3 min
Duration: 20-35 min
Metabolite: Laudanosine (CNS excitation)
Elimination: 66% ester hydrolysis, 33% hoffman elimination
What are 3 scenarios where you would NOT use atracurium due to the histamine release?
Hypertrophic cardiomyopathy (b/c of tachycardia) Aortic Stenosis (because of hypotension) Sever asthmatics (increases airway pressures)
What is the following for Cisatracurium? Dose: -Intubating dose: -Maintenance dose: Onset: Duration: Metabolite: Elimination:
-Intubating dose: .2mg/kg
-Maintenance dose: .1mg/kg
Onset: <3 min
Duration: 30-60 min
Metabolite: ??
Elimination: Hoffman elmination 77%. Smallest amount of renal clearance compared to others.
*Good for renal impairment pts
What are drugs that potentiate NDMR’s?
Drugs: aminoglycoside abx (polymyxins, clindamycins) local anesthetics (large doses) volatile gases (des, sevo, iso, N2O) mag sulfate lithium loop diuretics antiarrhythmic agents (quinidine, propranolol, procainamide)
What are patient factors that potentiate NDMR’s?
hypothermia female gender (from make-up)
What are electrolyte conditions that potentiate NDMR’s?
high magnesium
low calcium
low potassium
What are factors that decrease the effects of NDMR’s?
Chronic anticonvulsant therapy
Hyperparathyroidism and hypercalcemia
hyperkalemia
What response to paralytics will people with Myasthenia Gravis have?
They have less functional Ach receptors due to damage from antibodies-this makes them more sensitive to non-depolarizing muscle relaxants. They will be resistant to succinylcholine
What response to paralytics will people who have muscle denervation injuries have?
they have a chronic decrease in Ach release with a compensatory increase in Ach-nicotinic post-synaptic receptors (up regulation)
Resistance to NDMR’s (they have more Ach receptors that need to be blocked)
Exaggerated response to succ (more Ach receptors being depolarized)
What is the best location to check twitches for onset?
Facial nerve
What is the best location to check twitches for recover?
Ulnar nerve
What muscles are you checking with twitches at the facial nerve? What’s the action it causes?
Orbicularis Oris (closes eyelid) Corregator Supercilii (furrows brow)
What muscle are you checking with twitches at the ulnar nerve? What’s the action it causes?
Adductor Pollicis (Adducts thumb)
What is the pneumonic to remember the order in which muscles recover after paralytic is given? What do the letters stand for?
Vocal Cords Die Out After Adding Muscle Paralysis Externally Vocal Cords Diaphragm Orbicularis Oris Abdominal Rectus Adductor Pollicis Masseter Pharyngeal Extra-ocular
In order of 1st to recover, last to block
How can you distinguish between a Phase 1 or Phase II Succinylcholine block?
Phase II has fade
What train of four ratio is needed for safe extubation?
> 0.9
What percentage of receptors are blocked with the following train of four responses: 0 twitches 1 twitch 2 twitches 3 twitches 4 twitches
0=100% 1=90% 2=80% 3=75% (3 twitches present and still 75%blocked) 4=<70%
Which test most closely indicates a train of four ratio of 0.9?
Sustained jaw clench on tongue blade