Neuromuscular Blockade Flashcards
Neuromuscular blocking drugs are used in ___________ to cause muscle relaxation
Anesthesia
Neuromuscular blocking drugs target the _____________ _____________ to enable light anesthesia to be used with adequate relaxation of the abdomen and diaphragm
Neuromuscular junction (NMJ)
Neuromuscular blocking drugs relax the _________ ________ to allow passage of a ____________ _______
Vocal cords
Tracheal tube
Neuromuscular blocking drugs differ from muscle relaxants used in MSK disorders that act on the ________ or ________
Spinal cord
Brain
Patients who have received a neuromuscular blocking drug should always have their __________ assisted or controlled until the drug has been inactivated or antagonised.
respiration
Patients who are given neuromuscular blocking drugs should also receive sufficient concomitant inhalation or IV ____________ or ___________ drugs to prevent _____________
Anesthetic
Sedative
Awareness
What are the two major classes of neuromuscular blocking agents?
- Non-depolarizing (AKA competitive muscle relaxants)
2. Depolarizing
What is the mechanism of action of non-depolarizing neuromuscular blocking drugs?
Non-depolarizing neuromuscular blocking drugs (also known as competitive muscle relaxants) compete with acetylcholine for receptor sites at the neuromuscular junction
Non-depolarizing neuromuscular blocking drugs can be reversed with ________________ such as ___________
AchE inhibitors
Neostigmine
Non-depolarising neuromuscular blocking drugs can be divided into the __________ group and the ___________ group
aminosteroid
benzylisoquinolinium
Aminosteroid non-depolarizing neuromuscular blocking drugs include…? (3)
- pancuronium bromide
- rocuronium bromide
- vecuronium bromide
Benzylisoquinolinium non-depolarizing neuromuscular blocking drugs include…? (3)
- atracurium besilate
- cisatracurium
- mivacurium
Non-depolarising neuromuscular blocking drugs have a __________ (faster/slower) onset of action than suxamethonium chloride (a depolarizing neuromuscular blocking agent).
Slower
Non-depolarizing neuromuscular blocking drugs can be classified by their duration of action as short-acting ( ________ minutes), intermediate-acting ( _______ minutes), and long-acting ( _______ minutes), although duration of action is dose-dependent
15–30
30–40
60–120
Non-depolarizing neuromuscular blocking drugs that have a shorter or intermediate duration of action include…? (2)
- Atracurium
- Vecuronium
*more widely used than those with a longer duration (eg. pancuronium)
Which non-depolarizing neuromuscular blocking drug has a longer duration of action?
Pancuronium
Do non-depolarising neuromuscular blocking drugs have sedative or analgesic effects?
NO
Do non-depolarizing neuromuscular blocking drugs trigger malignant hyperthermia?
NO, unlike depolarizing
For patients receiving intensive care and who require tracheal intubation and mechanical ventilation, a ___________ (depolarizing/non-depolarising) neuromuscular blocking drug is chosen according to its onset of effect, duration of action, and side-effects
Non-depolarizing
______________, with a rapid onset of effect, may facilitate intubation
Rocuronium bromide
_____________ or ___________ may be suitable for long-term neuromuscular blockade since their duration of action is not dependent on elimination by the liver or the kidneys
Atracurium besilate
cisatracurium
Atracurium besilate or cisatracurium may be suitable for long-term neuromuscular blockade since their duration of action _______ (is/is not) dependent on elimination by the liver or the kidneys
Is NOT
Atracurium besilate, a mixture of 10 isomers, is a benzylisoquinolinium neuromuscular blocking drug with an __________ duration of action
intermediate
A non-depolarizing neuromuscular blocking drug
_____________ undergoes non-enzymatic metabolism which is independent of liver and kidney function, thus allowing its use in patients with hepatic or renal impairment
Atracurium besilate
Cardiovascular effects associated with _____________ (non-depolarizing neuromuscular blocking drug) include significant histamine release; histamine release can be minimised by administering slowly or in divided doses over at least 1 minute.
Atracurium besilate
_____________ is a single isomer of atracurium besilate. It is more potent and has a slightly longer duration of action than atracurium besilate and provides greater cardiovascular stability because it lacks histamine-releasing effects
Cisatracurium
Cisatracurium is a single isomer of atracurium besilate. It is ________ (more/less) potent and has a slightly ________ (longer/shorter) duration of action than atracurium besilate and provides _________ (greater/less) cardiovascular stability because it lacks histamine-releasing effects
More
Longer
Greater
Mivacurium, a benzylisoquinolinium neuromuscular blocking drug, has a _______ (long/short) duration of action
Short
___________ (a benzylisoquinolimium neuromuscular blocking drug) is metabolised by plasma cholinesterase and muscle paralysis is prolonged in individuals deficient in this enzyme.
Mivacurium
Mivacurium ______ (is/is not) associated with vagolytic activity or ganglionic blockade; histamine release can occur, particularly with rapid injection
Is NOT
Pancuronium bromide, an aminosteroid neuromuscular blocking drug, has a ________ (long/short) duration of action and is often used in patients receiving long-term mechanical ventilation in intensive care units
Long
Pancuronium bromide, an aminosteroid neuromuscular blocking drug, has a long duration of action and is often used in patients receiving long-term ___________ in _____________
mechanical ventilation
intensive care units
Pancuronium _______ (does/does not) cause a histamine-releasing effect, but __________ (does/does not) cause vagolytic and sympathomimetic effects
Does NOT
DOES; may cause tachycardia and hypertension
________________, an aminosteroid neuromuscular blocking drug, exerts an effect within 2 minutes and has the most rapid onset of any of the non-depolarising neuromuscular blocking drugs
Rocuronium bromide
Rocuronium bromide, a non-depolarizing neuromuscular blocking drug, has a/an _________ duration of action
Intermediate
*But most rapid onset (within 2 min)
Does rocuronium have CV and/or vagolytic effects?
Minimal CV effects
High doses may produce mild vagolytic activity
Vecuronium, an aminosteroid neuromuscular blocking drug, has a/an ________ duration of action
Intermediate
Does vecuronium produce histamine release or CV effects?
Generally no histamine release
Lacks CV effects
What is the mechanism of action of depolarizing neuromuscular blocking drugs?
Binding to ACh receptors to generate an action potential; because they are not metabolized by AChE, the binding of this drug to the receptor is prolonged resulting in an extended depolarization of the muscle end-plate
Depolarizing neuromuscular blocking drugs first cause _______ then ________
Muscle contraction
Paralysis
What is the most commonly-used depolarizing neuromuscular blocking agent?
Suxamethonium chloride (aka succinylcholine)
Suxamethonium chloride (succinylcholine) should be given _______ (before/after) anaesthetic induction because paralysis is usually preceded by painful muscle fasciculations
After
_________________ has the most rapid onset of action of any of the neuromuscular blocking drugs and is ideal if fast onset and brief duration of action are required, e.g. with tracheal intubation
Suxamethonium chloride (succinylcholine)
Unlike the non-depolarising neuromuscular blocking drugs, the action of suxamethonium (succinylcholine) ________ (can/cannot) be reversed
Cannot; recovery is spontaneous
Anticholinesterases such as neostigmine ____________ (reverse/potentiate) the neuromuscular block generated by suxamethonium (succinylcholine)
Potentiate
Unlike non-depolarizing neuromuscular blocking drugs which are reversed by agents like neostigmine that increase the amount of ACh in the synaptic cleft leading to displacement of these drugs from receptors
While ____________ (bradycardia/tachycardia) occurs with single use of suxamethonium (succinylcholine), ____________ (bradycardia/tachycardia) may occur with repeated doses in adults and with the first dose in children
Tachycardia
Bradycardia
*Premedication with atropine reduces bradycardia as well as the excessive salivation associated with suxamethonium chloride use
____________ may occur in dual block, which occurs with high or repeated doses of suxamethonium chloride and is caused by the development of a non-depolarising block following the initial depolarising block
Prolonged paralysis
Prolonged paralysis may occur in __________, which occurs with high or repeated doses of suxamethonium chloride and is caused by the development of a non-depolarising block following the initial depolarising block
dual block
Prolonged paralysis may occur in dual block, which occurs with _________ or ________ doses of suxamethonium chloride and is caused by the development of a non-depolarising block following the initial depolarising block
High
repeated
Prolonged paralysis may occur in dual block, which occurs with high or repeated doses of suxamethonium chloride and is caused by the development of a ____________ (depolarizing/non-depolarising) block following the initial ___________ (depolarising/non-depolarizing) block
Non-depolarizing
Depolarizing
Individuals with _____________ are resistant to suxamethonium chloride but can develop dual block resulting in delayed recovery.
myasthenia gravis
Individuals with myasthenia gravis are resistant to __________________ but can develop dual block resulting in delayed recovery.
suxamethonium chloride (succinylcholine)
Individuals with myasthenia gravis are resistant to suxamethonium chloride but can develop dual block resulting in ____________
delayed recovery
Prolonged paralysis may occur in those treated with suxamethonium (succinylcholine) with _________ or _________ plasma cholinesterase
Low
Atypical
*Assisted ventilation should be continued until muscle function is restored
How is dose calculated when prescribing non-depolarizing neuromuscular blocking drugs?
Based on ideal body-weight
Non-depolarizing neuromuscular blocking drugs should be prescribed with caution in which patients? (6)
Patients with:
- Burns (resistance can develop)
- CVD (reduce rate of administration)
- Fluid and electrolyte disturbances (response unpredictable)
- Hypothermia (activity prolonged, lower dose required)
- MG (activity prolonged, lower dose required)
- Neuromuscular disorders (response unpredictable)
What are the side effects of non-depolarizing neuromuscular blocking drugs? (8)
- Flushing (histamine release)
- Hypotension (histamine release)
- Bronchospasm (histamine release)
- Circulatory collapse (histamine release)
- Muscle weakness and myopathy (after prolonged use in ICU)
- Shock
- Cardiac arrest
- Seizures
**pancuronium lacks histamine-releasing effects, but vagolytic and sympathomimetic effects can cause tachycardia
What are the symptoms of histamine release associated with rapid administration of non-depolarizing neuromuscular blocking agents? (4)
- Flushing
- Hypotension
- Bronchospasm
- Circulatory collapse
Manufacturer advises minimising effects of histamine release by administering over 1 minute in patients with cardiovascular disease or sensitivity to hypotension.
Do non-depolarizing neuromuscular blocking drugs cross the placent?
No; Non-depolarising neuromuscular blocking drugs are highly ionised at physiological pH and are therefore unlikely to cross the placenta in significant amounts
What side effects are associated with pancuronium bromide specifically? (5)
- Apnea
- Arrhythmia
- Hypersalivation
- Increased CO
- Miosis
**lacks histamine-releasing effects, but vagolytic and sympathomimetic effects can cause tachycardia
What are the contraindications to use of suxamethonium (succinylcholine)? (9)
- Hyperkalemia
- Low plasma-cholinesterase activity (including severe liver disease)
- Major trauma
- Neurological disease involving acute wasting of major muscle
- Personal or family history of malignant hyperthermia
- Personal or family history of congenital myotonic disease
- Prolonged immobilisation (risk of hyperkalemia)
- Severe burns
- Skeletal muscle myopathies (eg Duchenne MD)
What is malignant hyperthermia?
A severe reaction to all inhalation anesthetics EXCEPT nitrous oxide AND depolarizing neuromuscular junction blocking agent, suxamethonium chloride (succinylcholine)
What is the cause of malignant hyperthermia?
Genetic defect leading to an abnormal ryanodine receptor in skeletal muscle
This abnormality interferes with regulation of calcium in the muscles, leading to buildup of calcium in skeletal muscles and a clinical syndrome of hypermetabolism
What are the symptoms of malignant hyperthermia? (7)
- Severe muscle rigidity or spasm
- Rapid shallow breathing and secondary respiratory failure
- Tachycardia
- Arrhythmia
- Hyperthermia
- Excessive sweating
- Mottled skin
What is the route of administration of neuromuscular blocking drugs?
IV
In which patients should suxamethonium (succinylcholine) be administered with caution? (5)
Patients with:
- Cardiac disease
- Neuromuscular disease
- Raised IOP (avoid in penetrating eye injury)
- Respiratory disease
- Severe sepsis (risk of hyperkalemia)
What are the side effects of suxamethonium chloride (succinylcholine)? (14)
- Arrhythmias
- Bradycardia (with repeated doses)
- Flushing
- Involuntary muscle contractions
- Myoglobinemia
- Myoglobinuria
- Post-procedural muscle pain
- Rash
- Apnea
- Cardiac arrest
- Hypersensitivity
- Malignant hyperthermia
- Respiratory disorders
- Trismus
Premedication with ________ reduces bradycardia associated with suxamethonium use.
atropine
How does pregnancy affect the effect of suxamethonium?
Mildly prolonged maternal neuromuscular blockade
Does hepatic impairment affect the effect of suxamethonium (succinylcholine)?
Yes, increased risk of prolonged apnoea due to reduced hepatic synthesis of plasma cholinesterase
Manufacturer advises caution, particularly in end stage hepatic failure
Anticholinesterase inhibitors reverse the effects of ______________ (depolarizing/non-depolarizing) neuromuscular blocking drugs such as ___________ but they prolong the action of ____________ (depolarizing/non-depolarizing) neuromuscular blocking drugs such as _____________.
non-depolarising (competitive); pancuronium
depolarising; suxamethonium chloride
____________ is used specifically for reversal of non-depolarising (competitive) blockade
Neostigmine
Neostigmine acts within ___________ of intravenous injection and its effects last for __________; a second dose may then be necessary
one minute
20 to 30 minutes
_______________ or alternatively _________, given before or with neostigmine, prevent bradycardia, excessive salivation, and other muscarinic effects of neostigmine.
Glycopyrronium bromide
atropine sulfate
____________ is a modified gamma cyclodextrin that can be used for rapid reversal of neuromuscular blockade induced by rocuronium bromide or vecuronium bromide
Sugammadex; in practice, sugammadex is used mainly for rapid reversal of neuromuscular blockade in an emergency.
What is the mechanism of action of neostigmine?
AChE inhibitor
In the context of non-depolarizing neuromuscular blockade reversal, inhibition of AChE leads to build-up of ACh at the NMJ and displacement of muscle relaxants from ACh receptors
In addition to reversing the action of non-depolarizing neuromuscular blockade, neostigmine is also used in the treatment of ___________
Myasthenia gravis
AChE inhibitors, including neostigmine, are contraindicated in ___________ and ____________
Intestinal and urinary obstruction
AChE inhibitors, including neostigmine, should be used with extreme caution in which patients? (10)
Patients with:
- Arrhythmias
- Asthma (extreme caution)
- Bradycardia
- Epilepsy
- Hypothyroidism
- Hypotension
- Parkinsonism
- Peptic ulceration
- Recent MI
- Vagotonia
Why isn’t atropine given routinely with neostigmine?
Because it may mask signs of overdosage
What are the signs and symptoms of ACh toxicity (AChE inhibitor overdose)? (11)
- Cramps and muscle weakness
- Hypersalivation
- Lacrimation
- Paralysis
- Muscle fasciculations
- Diarrhea, involuntary defecation
- Blurry vision, miosis, nystagmus
- Bradycardia, hypotension
- Bronchospasm, increased bronchial secretions
- Excess sweating
- Involuntary micturition
May be remembered by DUMBBEELLS or SLUDGE
(Think parasympathetic hyperstimulation)
___________ or ____________ should also be given when reversing neuromuscular blockade with IV neostigmine
Glycopyrronium
atropine