Muscle Blockers Flashcards
why don’t muscle blockers effect the brain or CNS?
polar compounds can’t go thru BBB so must give IV
how long do short acting non depolarizing neuromuscular blockers work? long acting? what is the only long acting neuromuscular blocker?
short: 30-60 minutes
long: 60-120 minutes
only long acting: pancuronium
increasing the length of use of non depolarizing muscle blocker does what to duration of action?
prolongs it
remember for ICU
how to reverse effects of non depolarizing agent?
acetylcolinesterase inhibitors to increase ACh concentration
what mm is last affected by non depolarizing blockers?
diaphragm
DOA of succinylcholine?
5-10 minutes
MOA of succinylcholine
binds & activates the nicotinic receptor once causing one transmission of an impulse to the muscle.
Doesn’t transmit anymore and doesn’t leave the receptor either.
It sits there blocking the channel
Normal closure of the gate is prevented and the blocker moves in and out rapidly
Muscle stays in depolarized state, unable to repolarize while succinylcholine sits there.
how long do fasciculations last after dosing succinylcholine? how long until paralysis?
30 seconds of fasciculations
90 seconds until paralysis
CVS affects of nondepolarzing blockers?
hypotension (prevent with antihistamines)
tachycardia
CVS affects of depolarizing blockers?
arrhythmia when given with other anesthetics
what drug causes hyperkalemia? who does it happen to?
succinylcholine if given to pt with burns, nerve damage, neuromuscular disease, or trauma
what drug causes most mm pain after paralysis?
succinylcholine
succinylcholine + volatile anesthetics =
malignant hyperthermia from abnormal release of Ca from stores in skeletal mm
treatment: dantrolene
muscular blockers + aminoglycosides (Abx) =
increased blockade
Abx decrease the release of ACh and can lead to respiratory depression
increased age + NM blockers =
increased effect (decrease dose if older than 70)
NM+ myasthenia gravis =
increased effect
NM + severe burn or UMNL =
decreased effect
benefits of NM blockers in ventilation
increases O2
decreases atelectasis
NM blocker + intubation =
upper airway muscle relaxation
safer to put tube down first
cause of muscle spasticity?
increased tonic stretch of reflex (DTR) or flexor mm spasm (increased tone)
often get with mm weakness
caused by spinal injury
CP
MS
stroke
MOA of spasmolytics
change stretch reflex arc (DTR) or act on mm directly (dantrolene)
decrease pain but don’t fix dysfunction
Diazepam MOA
increases GABA which hyper polarizes cell (decreases excitability of mm)
use of diazepam?
any spasticity (spinal cord transection, CNS origin) q
SE of diazepam as spasmolytic?
CNS sedation
Baclofen MOA?
agonizes GABA (decreases excitatory NT in brain and substance P in spinal cord)
clinical use of baclofen?
given PO (intrathecal if severe)
as effective as diazepam w/o sedation
no effect on mm strength like dantrolene
addiction or spasms
SE of baclofen?
drowsiness (tolerance occurs)
anticholinergic effects
increased seizure potential when drug is stopped (if epileptic)
- withdraw dose slowly
MOA of tizanidine?
CNS alpha 2 adrenergic agonist (like clonidine)
use of tizanidine?
spasticity from cerebral or spinal injury (equally effective to the others)
SE of tizanidine?
drowsiness
hypotension
dry mouth
asthenia (perceived loss of strength)
MOA of dantrolene?
works in mm fibers
prevents release of calcium in skeletal mm (prevents contraction)
little effect on cardiac/smooth mm
clinical uses of dantrolene?
spams (CNS or spinal cord), and malignant hyperthermia
SE of dantrolene
generalized mm weakness, sedation, symptomatic hepatitis (with >800mg/d)
what is malignant hyperthermia?
prolonged release of Ca from mm leads to massive contraction
increased lactic acid
fever
death
use of cyclobenazprine and its look alikes
acute mm spasm caused by tissue trauma or strain (not for spasms from spinal cord or brain injuries)
usually nonspecific back pain
SE of cyclobenazprine and its look alike?
strongly anticholinergic
drowsy
confusion
visual hallucinations
drugs used for severe mm spasms due to euro injury?
diazepam
baclofen
tizanidine
dantrolene
drugs used for mm pain/injury syndromes where spasms is cause of pain or secondary to local mm:
ophenadrine carisoprodol cyclobenzaprine metaxalone methocarbamol
what population do u need to be careful with, with spasmolytics?
elderly (increased SE)