Neuromuscular blockers 4 Flashcards
What are the two classes of nondepolarizing neuromuscular blockers?
aminosteroid compounds: rocuronium, vecuronium, pancuronium
benzylisoquinolinium compounds: atracurium, cisatracurium, mivacurium
Hofmann elimination is base-catalyzed reaction that’s dependent on
normal blood pH & temperature
Benzylisoquinolinium compounds undergo
spontaneous degradation in the plasma (Hofmann elimination & non-specific plasma esterases)
___________ is a metabolite of both atracurium and cisatracurium
Laudanosine (more so w/ atracurium)
Laudanosine can produce
seizures (CNS stimulant)
The termination of action for aminosteroid neuromuscular blockers depends on
hepatic metabolism
biliary excretion
and/or renal excretion
________________ compounds are better choices for patients with hepatic or renal dysfunction.
Benzylisoquinolinium
Atracurium is hydrolyzed by
Hofmann elimination (33%) & non-specific plasma esterases (66%)
Cisatracurium metabolism is dependent on
Hofmann elimination
Mivacurium is metabolized by
pseudocholinesterase (explains it’s relatively short DOA)
Hofmann elimination is faster with
alkalosis & hyperthermia
Hofmann elimination is slower with
acidosis and hypothermia
Is the metabolite laudanosine a concern in the OR?
no; only concerned with prolonged infusion in the ICU
Rocuronium is eliminated through
biliary excretion as an unchanged molecule
Vecuronium undergoes
hepatic deacetylation to 3-OH vecuronium (1/2 as potent as parent compound but rapidly metabolized)
Pancuronium undergoes
hepatic deacetylation to 3-OH pancuronium (1/2 as potent as parent compound)
Rocuronium is metabolized
it’s not!
eliminated via the liver >70% & renal elimination 10-25% & biliary excretion
Vecuronium is metabolized
via the liver (30-40%)
Pancuronium is metabolized via the
liver (10-20%)
List 4 neuromuscular blockers that undergo organ-independent elimination?
atracurium
cisatracurium
mivacurium
succinylcholine
Which drugs potentiate neuromuscular blockade? select 3
a. desflurane
b. gentamycin
c. phenytoin
d. mannitol
e. dantrolene
f. hydrocortisone
a. desflurane
b. gentamycin
e. dantrolene
Factors that potentiate neuromuscular blockade increase
the difficulty of reversal as well as the risk of residual weakness
What are the three groups of potentiating factors for neuromuscular blockade?
drugs
electrolytes
patient factors
Patient factors that potentiate neuromuscular drugs include?
hypothermia (decreases metabolism & clearance)
gender (women are more sensitive to the effects of NMBs)
Electrolytes that potentiate neuromuscular drugs include:
increased lithium
increased magnesium
decreased calcium
decreased potassium
Drugs that potentiate neuromuscular drugs include
volatile anesthetics
antibiotics
antidysrhythmics
local anesthetics
diuretics
other drugs: dantrolene, cylcosporin, tamoxifen
Which local anesthetics potentiate neuromuscular drugs?
probably all of them
Which diuretics potentiate neuromuscular drugs?
furosemide
What other drugs potentiate neuromuscular drugs?
dantrolene, cyclosporin, tamoxifen
Which antidysrhythmics potentiate neuromuscular drugs?
verapamil, amlodipine, lidocaine, quinidine
Which antibiotics potentiate neuromuscular durgs?
aminoglycosides
polymyxins
clindamycin
lincomycin
tetracycline
Which inhaled anesthetic potentiates NMBs the most?
desflurane
Which inhaled anesthetic potentiates NMBs the least?
nitrous oxide
Which condition precludes the use of pancuronium?
a. aortic regurgitation
b. hypertrophic cardiomyopathy
c. first degree AV block
d. bradycardia
b. hypertrophic cardiomyopathy
Pancuronium is a _____-
vagolytic (it increases heart rate)
________, ___________, ____________ release histamine
succinylcholine, atracurium, & mivacurium
The release of histamine leads to
tachycardia & vasodilation
Patients who are ___________________ should not receive histamine-releasing drugs unless the clinical benefits outweighs the risk.
sensitive to a higher heart rate or reduced afterload
Succinylcholine stimulates ________________ which can produce tachycardia
autonomic ganglia
Succinylcholine can also stimulate ______________ which can produce bradycardia
M2 receptors in the SA node
Pancuronium is unique in that it has a _________ effect in the SA node
vagolytic effect & stimulates the release of catecholamines
The patient with ___________ should not receive pancuronium
hypertrophic cardiomyopathy
Which neuromuscular blocker is MOST likely to cause anaphylaxis?
a. atracurium
b. cisatracurium
c. succinylcholine
d. rocuronium
c. succinylcholine
__________________________ are the most common cause of perioperative allergic reactions
Neuromuscular blockers
Which NMBs are associated with the highest incidence of anaphylaxis?
succinylcholine & rocuronium
Do neuromuscular blocker drugs have cross-sensitivity?
yes, may occur in up to 70% of those who have experienced a previous allergic response
How do allergic reactions develop as a result of NMBs?
the structures of NMBs contain one or more antigenic quaternary ammonium groups that interact with IgE causing mast cell and basophil degranulation
It’s possible that sensitivity to any NMBs can develop following
exposure to soaps or cosmetics (because they contain antigenic quaternary ammonium groups)
What enzyme is measured to diagnose an anaphylactic reaction?
tryptase (an elevated tryptase level reflects mast cell and basophil degranulation (peaks between 15-120 minutes after exposure
