Flashcards in Muscle Relaxants Deck (43)
Acetylcholine binds what receptor at the neuromuscular junction? What subunit?
Nicotinic (2 Ach needed). Alpha subunits
What is phase 1 block?
High proportion of Ach (I.e. Succinylcholine) to be activated at once
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?
Twitch monitor on adductor pollicus longus or occuli orbicularis is more resistant to non-depolarizing NMB?
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)
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.
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?
Non-depolarizing NMB with the most liver metabolism
Non-depolarizing NMB with the greatest renal excretion
How is rocuronium metabolized and excreted?
No metabolism, cleared by the liver via bile
How is vecuronium excreted?
25% renal, 75% bile
Which NMB can precipitate with thiopental?
Rocuronium and vecuronium
Full dose of naloxone?
Which would you not see with glycopyrrolate? Bronchodilation, tachycardia, decreased GI motility, decreased salivation, mydriasis?
Mydriasis; glycopyrolate has a quaternary structure and cannot cross the BBB
What is recurization?
Rocuronium is excreted via bile with no metabolism and can reabsorbed again, causing residual NMB actions
Neostigmine onset time and peak effect time?
Onset: 5 min
Peak: 10 min
Does neostigmine cross the placenta? Can glycopyrolate cross the placenta?
75yo male given scopolamine is confused and disoriented, what is the treatment?
Physostigmine (crosses the BBB to increase Ach - since scopolamine is an anti-cholinergic)
Most hemodynamically stable non-depolarizing NMB?
Vecuronium (no vagolysis and no histamine release) - Rocuronium has vagolysis
Intubating dose of Succinylcholine?
Intubating dose of Rocuronium?
1.2 mg/kg (RSI)
Intubating dose of Cisatracurium?
Intubating dose of Vecuronium?
Intubating dose of Pancuronium?
Non-depolarizing NMB with the longest duration of action?
Non-depolarizing NMB with the most vagolytic side effect?
When should you avoid succ in children?
Men younger than 5 years (undiagnosed Duchenne muscular dystrophy)
Difference in cardiac side effects seen with succinylcholine in adults vs. children?
Children: sympathotonic so they will brady after succ
Adults: vagotonic so they will become tachy
What is the best clinical indicator of adequate muscle function after NMB use?
Sustained head lift (at least 70% function has returned)
What T4/T1 ratio ensure the patient can maintain adequate ventilation?
What is the gold standard of monitoring NMB?
How is the duration of action of esmolol affected by a patient with a dibucaine number of 20%?
Not affected at all. Esmolol is metabolized by esterases in the RBCs (different from pseudocholinesterase that breaks down succinylcholine in this homozygous)
How are NMB's affected by Lambert-Eaton Syndrome?
Increased sensitivity to depolarizing and non-depolarizing NMBs (decreased ACh at the junction -> increased sensitivity to non-depolarizing -> increased extra-junctional receptors -> increased sensitivity to depolarizing)
Does cerebral palsy increase the risk of hyperkalemia with succinylcholine use?
No since there is no increase in the extra-junctional receptors