Nondepolarizing NMBD Reversal Agents Flashcards
What is the Enzyme responsible for rapid acetylcholine hydrolysis?
Acetylcholinesterase
How many molecules of acetylcholine are hydrolyzed per second?
Very efficient-4,000 molecules
Where is Acetylcholinesterase highly concentrated?
within the neuromuscular junction
What is another name for Anticholinesterases?
Acetylcholinesterase Inhibitors
What is the mechanism of action of Anticholinesterases?
Inhibition of acetylcholinesterase increases the amount of acetylcholine in the neuromuscular junction
Anticholinesterases: What effect does Increased acetylcholine have?
competes with residual neuromuscular blocking drug molecules for a binding site on the nicotinic receptors
What causes the side effects of Anticholinesterases?
Concomitant increase of acetylcholine at muscarinic receptors (results in the side effects)
What are some examples of Acetylcholinesterase inhibitors? (3)
neostigmine, edrophonium, pyridostigmine
Why are Acetylcholinesterase inhibitors used clinically?
to antagonize the residual effects of neuromuscular blockers and to accelerate recovery from nondepolarizing neuromuscular blockade
What effects recovery of muscle relaxation?
induced by nondepolarizing neuromuscular blockers ultimately depends on the elimination of the neuromuscular blocker from the body
What should dosing anticholinesterases be based on?
DEPTH OF BLOCK
How is depth of block determined?
MONITORING NEUROMUSCULAR EVOKED RESPONSES: TRAIN OF FOUR (TOF)
What is an objective monitoring system for nerve block?
acceleromyography (gold standard)
What is another example of block depth monitoring?
measured TOF ratio number (0.1-1.0)
What is subjective block monitoring?
Subjective monitoring: visual/tactile evoked responses observed to stimulation of a peripheral nerve using a peripheral nerve stimulator
Objective ________, use subjective if not available
preferred
What is the train of four count for intense (profound) block and deep block?
0
What is the train of four count for moderate block?
1-3
What is the train of four count for light (shallow), minimal (near recover) and full recover (normal function) block?
4
What is the measured train of four count (objective) for moderate, intense (profound) block and deep block?
0
What is the measured train of four count (objective) for light (shallow) block?
0.1-0.4
What is the measured train of four count (objective) for minimal (near recovery) block?
> 0.4 and <0.9
What is the measured train of four count (objective) for full recovery (normal function) block?
> 0.9-1.0
What is the only measured train of four reading where reversal is not needed?
> 0.9-1.0
What is the most common acetylcholinesterase inhibitor?
Neostigmine (Prostigmine)
What does Neostigmine (Prostigmine) also inhibit?
inhibits plasma cholinesterase
What is the IV dose of Neostigmine (Prostigmine) for moderate neuromuscular blockade (TOF >2)?
0.05-0.07 mg/kg for antagonism of moderate neuromuscular block
What is the IV dose of Neostigmine (Prostigmine) for light-minimal neuromuscular blockade (TOF of 4 with tactile or visual fade)?
0.02-0.03 mg/kg
What is the maximum dose of Neostigmine (Prostigmine)?
5 mg
What is the onset of Neostigmine (Prostigmine)?
Slower acting (7-11 minutes)
What is Neostigmine (Prostigmine) usually paired with? Why?
with glycopyrrolate (7-15 ug/kg) due to onset timing (attenuate muscarinic side effects)
Why is additional doses of neostigmine not recommended?
Administering additional doses of neostigmine are not recommended because the concentration of acetylcholine that can be produced at the neuromuscular junction is finite
What can the anticholinesterases not antagonize?
Because of this ceiling effect, the anticholinesterases CANNOT effectively antagonize profound or deep levels of neuromuscular blockade
Moderate nondepolarizing blockade with a TOF ________ should not be reversed with neostigmine
below 2
What can happen with a neostigmine dose of >5mg?
may actually prolong degree of blockade
What is the drug class of Edrophonium (Enlon, Tensilon)?
Acetylcholinesterase inhibitor
When was Edrophonium (Enlon, Tensilon) discontinued?
Discontinued in 2018
What is the onset of Edrophonium (Enlon, Tensilon)?
Rapid acting, faster onset than neostigmine (1-2 minutes)
What is the potency of Edrophonium (Enlon, Tensilon)?
1/12 the potency of neostigmine
What is the dose of Edrophonium (Enlon, Tensilon)?
1-1.5 mg/kg
What is Edrophonium (Enlon, Tensilon) usually paired with?
atropine (7-10 ug/kg) due to onset
What is Enlon Plus?
edrophonium plus atropine mixed
What is the elimination half-life of Edrophonium (Enlon, Tensilon)?
Elimination half life of edrophonium is similar to neostigmine (approximately 50-100 minutes)
What is the excretion of Edrophonium & Neostigmine?
Renal excretion accounts for about 50% of the excretion of neostigmine and 75% of edrophonium
What effect is seen with renal failure for those given Edrophonium & Neostigmine?
Renal failure decreases the plasma clearance of neostigmine and edrophonium
What does inhibition of acetylcholinesterase do?
increases the concentration of acetylcholine at the neuromuscular junction (nicotinic site) and to all other synapses that acetylcholine acts as a transmitter (muscarinic)
What are the cardiovascular muscarinic effects of anticholinesterases? Why is this caused?
Bradycardia due to activation of the muscarinic and nicotinic acetylcholine receptors in the parasympathetic nervous system
What are the two most common anticholinesterases?
Edrophonium & Neostigmine
What can be administer to minimize the cardiovascular muscarinic effects of anticholinesterases?
Administer an anticholinergic agent to minimize muscarinic CV side effects
What are the pulmonary muscarinic effects of anticholinesterases? (5)
Bronchoconstriction, bronchospasm, Increased airway resistance, increased salivation, and increased bowel (attenuated by administering an anticholinergic)
What is a caveat to administration of Anticholinesterases?
Unnecessary (too much) administration of anticholinesterase can cause muscle weakness
What is the MOA of muscle weakness from too much) administration of anticholinesterase ?
Weakness of the airway dilator muscle genioglossus can lead to upper airway collapse during inspiration
Unnecessary administration of neostigmine can also cause ____________
diaphragmatic dysfunction
Reversal Guide: What is the neostigimine dose for posttentanic count <2?
Delay reversal
Reversal Guide: What is the Sugammadex dose for posttentanic count <2?
4-16 mg/kg
Reversal Guide: What is the Sugammadex dose for posttentanic count >2?
2-4 mg/kg
Reversal Guide: What is the neostigimine dose for posttentanic count >2?
Delay reversal
Reversal Guide: What is the neostigimine dose for TOF count of 2-4?
0.05-0.07 mg/kg
Reversal Guide: What is the Sugammadex dose for TOF count of 2-4?
1-2 mg/kg