Muscle Relaxants Flashcards
What is phase 1 block?
High proportion of Ach (I.e. Succinylcholine) to be activated at once
Acetylcholine binds what receptor at the neuromuscular junction? What subunit?
Nicotinic (2 Ach needed). Alpha subunits
Myasthenia gravis and depolarizing NMB vs. non-depolarizing NMB
Depolarizing: decreased sensitivity
Non-depolarizing: increased sensitivity
Best place to put twitch monitor that mimics diaphragm and larynx muscles?
Occuli orbicularis (innervated by facial nerve)
Absence of 4th twitch on ToF = what percentage of receptors blocked?
3rd twitch? 2nd twitch? No twitches?
75-80%
85%
90%
None: 95%
Twitch monitor on adductor pollicus longus or occuli orbicularis is more resistant to non-depolarizing NMB?
Occuli orbicularis
Succinylcholine duration of action with ecothiophate use? Atropine use? Cirrhosis? Pregnancy?
Cholinesterase inhibitor so prolonged duration
Atropine increases Ach so decreases duration
Decreased pseudocholinesterase so prolongs duration
Dilutional decrease of pseudocholinesterase so prolongs duration
Dibucaine number of 20%? 50% 80%?
20%: Homozygous for abormal pseudocholinesterase so prolonged action of succinylcholine (4-8 hours)
50%: Heterozygous so prolonged action (30 min)
80%: Normal
Time frame and type of injury to worry about with succinylcholine use
24 hours after injury up until 1 year
Burns, prolonged sepsis, spinal cord injuries, myopathies, major trauma
Succinylcholine and what side effect(s) are most associated with fasciculations? Increased ICP, increased IOP, masseter spasms, myalgias, increased abdominal pressures
Increased ICP and abdominal pressures
Effect on duration of non-depolarizing NMB: volatile anesthetics, hypercalcemia, hypermagnesemia, hyperthermia, acidosis, hyperkalemia.
Prolonged Shortened/normal Prolonged Shortened/normal Prolonged Shortened/normal
General side effects of benzylisoquinolone muscle relaxants (-curium) vs. steroid muscle relaxants (-curonium)
Curium: histamine release (mostly atracurium and mivacurium)
Curonium: vagolytic (mostly pancuronium)
Non-depolarizing NMB and left sided hemiparesis, myasthenia gravis, cerebral palsy, 3rd degree burns 2 weeks ago, SLE.
Resistance to non-depolarizing NMB on left (proliferation of extra-junctional AchR)
Increased sensitivity to depolarizing and resistance to non-depolarizing
Resistance to non-depolarizing and normal to depolarizing
Resistance to non-depolarizing, hyperkalemia with succ
Sensitivity to both
What do you worry about with atracurium & cisatracurium?
Laudanosine is a breakdown product metabolized by the liver and excreted by kidneys; can results in CNS excitation if built up (atracurium is more likely to cause problems because you need larger doses than cis-)
What NMB can cause a polyneuropathy with weakness with prolonged drip usage?
Vecuronium
Non-depolarizing NMB with the most liver metabolism
Pancuronium
Non-depolarizing NMB with the greatest renal excretion
Pancuronium