Skeletal Muscle Relaxants Flashcards
what are neuromuscular blockades
- depolarizing blocker: succinylcholine
- non depolarizing blocker: benzylisoquinolines and ammonio steroids
what are the benzylisoquinolines and the ammonio steroids
Benzylisoquinolines: Cisatracurium, Atracurium, Mivacurium, Tubocurarine
Ammonio Steroids (curoniums) - Pancuronium, Vecuronium, Rocuronium
mechanism of action of non depolarizing blockers
- competitive antagonist of nicotonic receptors
- large doses, enter the pores of ion channels for a more intense motor blockade
- block prejunctional Na channels –> reducing release of acetylcholine
how can non depolarizing blockade be reversed
using acetylcholinesterase inhibitors – neostigmine and edrophonium –> increase amount of acetylcholine in the cleft
what is the phase I block or depolarization block of succinylcholine
bind to nicotinic receptors –> depolarize as acetylcholine would –> not metabolized effectively –> muscle unresponsive to additional impulses –> flaccid paralysis
what hydrolyzes succinylcholine/ reverses phase I or depolarization block of succinylcholine
plasma butyrylcholinesterase aka pseudocholinesterase
what is the phase II block or desensitization block of succinylcholine
single large dose, repeated doses, or prolonged infusion of succinylcholine repolarizes the membrane –> membrane can’t become depolarized because it is desensitized –> channel act like in prolonged closed state
what can reverse phase II block or desensitization block of succinylcholine
acetylcholinesterase inhibitors – neostigmine and edrophonium
which of the non depolarizing blocker has a metabolite that can cause hypotension and seizures
Atracurium –> metabolite is Laudanosime –> transient hypotension and seizures (if higher doses)
how is Atracurium inactivated
non specific plasma esterases and by spontaneous reaction called Hoffman elimination –> hence duration not altered by absence of renal function
Cisatracurium (stereoisomer)
only non depolarizing blocker classified as short acting and its significance
Mivacurium –> hydrolyzed by butyrylcholinesterase –> not dependent on liver or kidney for elimination
most rapid onset among all the non depolarizing blocker and can replace succinylcholine
Rocuronium
AE of non depolarizing blockers
Histamine Release (Tubocurarine) Ganglion blockade (Tubocurarine) --> hypotension and tachycardia Cardiac Muscarinic Receptor blocker (Pancuronium) --> moderate tachycardia
AE of depolarizing blocker
-succinylcholine stimulates nicotinic receptors in sympathetic and parasympathetic and muscarinic in heart
Malignant Hyperthermia (esp with halogenated hydrocarbons anesthetics)
Bradycardia
Histamine Release
Muscle pain
Hyperkalemia (loss of tissue K during depolarization)
Increased intraocular pressure
Increased intragastric pressure
how do you treat malignant hyperthermia
dantrolene - prevents release of Ca from sarcoplasmic reticulum
signs of histamine release
erythema of face and upper chest
transient hypotension
increased HR
how can tetracyclines produce neuromuscular blockade
chelating calcium so no calcium release for action potential
how can antibiotic aminoglycoside cause neuromuscular blockade
inhibiting ACh release from preganglionic terminal by competing with calcium
types of patients that are resistant to non depolarizing muscle relaxants and require additional non depolarizing relaxants
severe burn and UMN disease
what disease increases neuromuscular blockade caused by non depolarizing muscle relaxants
Myasthenia Gravis
contraindication of succinylcholine
- family or personal history of Malignant Hyperthermia, Skeletal Muscle Myopathies, and Hypersensitivity to drug
- major burns, multiple trauma, extensive denervation of skeletal muscle, UMN injury because succinylcholine can cause hyperkalemia and this results in cardiac arrest in these patients
muscarinic antagonist used post surgery and why
Atropine or Glycopyrrolate –> used together with neostigmine and edrophonium (used to reverse the non depolarizing blockade) –> prevent stimulation of muscarinic receptors and avoid bradycardia
what is succinylcholine mainly use for
endotracheal intubation
ECT
Spasmolytics that work in the CNS
Diazepam
Baclofen
Tizanidine
when is diazepam used as a spasmolytic
muscle spasm of any origin –> produces sedation in most patients in doses required to reduce muscle tone
mechanism of Baclofen
GABA agonist –> hyperpolarization due to increased K conductance
when is Balcofen used
spasticity in Multiple Sclerosis
Spinal cord injuries and diseases
mechanism and use of Tizanidine
alpha 2 agonist in the CNS –> MS and spinal cord injury
spasmolytics that work on skeletal muscle
Dantrolene
Botulinum Toxin
when is dantrolene used
Malignant Hyperthermia
when is Botulinum Toxin used
Blepharospasm - persistent and disabling eyelid spasm
Local muscle spasm
Cerebral Palsy
spasmolytics used for acute local spasm
Cyclobenzaprine
what is cyclobenzaprine used for
acute, painful, musculoskeletal conditions
AE of cyclobenzaprine
sedation, confusion, and transient visual hallucinations
