Muscle Relaxants Flashcards
What are 3 ways to cause muscle relaxation?
- increase volatile anesthetic
- regional anesthesia
- NMBA
Classes of NMBAs
- depolarizing
- nondepolarizing (aminosteroids & benzylisoquinolines)
What drug(s) are depolarizing NMBAs?
succinylcholine
What drug(s) are nondepolarizing aminosteroids?
- rocuronium
- vecuronium
- pancuronium
What drug(s) are nondepolarizing benzylisoquinolines?
- mivacurium
- atracurium
- cisastracurium
How does succinylcholine work?
binds to 2 alpha subunits of nicotinic cholinergic receptors (like ACh), allowing Na+ and Ca++ to flow in, K+ to flow out, and causing depolarization of the muscle
Succinylcholine mimics the action of __________
acetylcholine
When administered succinylcholine, the muscle remains depolarized until ________________
succinylcholine diffuses away from the receptor
When is succinylcholine used?
- rapid muscle relaxation
- routine intubation
- very short cases
- OB
- RSI
- laryngospasm
T/F: There is a reversal agent for succinylcholine
false
there is no reversal agent for succinylcholine; just has to diffuse away
Which NMBA has the potential to trigger malignant hyperthermia?
succinylincholine
Succinylcholine has potential to __________ HR due to _____________ stimulation
- decrease HR
- muscarinic stimulation
What is Phase I of succinylcholine administration?
normal expected phase from proper dosing; no fade on TOF
What is Phase II of succinylcholine administration?
happens from large or repeated doses of SCh; fade will be seen on TOF
The most common side effect of succinylcholine
fasciculations
Fasciculations can cause _____________
myalgia (muscle pain)
T/F: Succinylcholine has minimal histamine release
true
What are the potential side effects in children when given succinylcholine?
- hyperkalemia
- bradycardia
- cardiac arrest
How is succinylcholine metabolized?
hydrolyzed in plasma by buyrylcholinesterase aka plasma cholinesterase aka psuedocholinesterase
Succinylcholine Dosing
1 - 1.5 mg/kg for RSI
20 mg for laryngospasm
Succinylcholine onset and duration
Onset: 30-60 sec
Duration: < 10 min
Succinylcholine IM Dosing
3-5 mg/kg
Succinylcholine IM onset and duration
Onset: 2-5 min
Duration: 10-30 min
____________ is a weak active metabolite of succinylcholine
succinylmonocholine
What can prolong blocking effects of succinylcholine?
anything that can cause decreased levels of pseudocholinesterase (pregnancy, liver disease) and pseudocholinesterase abnormality
T/F: Pregnancy can prolong blocking effects of succinylcholine
true
pregnancy decreases pseudocholinesterase levels, causing decreased metabolism of SCh
What are the triggers for MH?
- succinylcholine
- volatile inhalational agents
T/F: Nitrous oxide can trigger MH
false
What are the first signs of MH?
- unexplained increase in CO2
- unexplained increase in temp
- masseter spasm/rigidity
- unexplained sudden tachycardia
How do nondepolarizing NMBAs work?
compete with and block ACh at the alpha subunits of the nicotinic receptors on the motor endplate, inhibiting depolarization