Pharm: neuro blocks (week 9)

Question 1

ED95 for NMB agents

Answer 1

• 95% twitch height suppression (from baseline)

- usually give 2-3x for intubation

Question 2

contraindications for succinylcholine use

Answer 2

absolute: difficult airway, allergy, suspected MH, burns, muscular dystrophy, spinal cord injury, denervation (due to hyperkalemia risk with extrajunctional receptors)
relative: raised ICP, glaucoma/open eye injury, hyperkalemia, severe trauma, neurl. diseases, bradycardia, pseudocholinesterase deficient

Question 3

relationship between potency and onset for NMB

Answer 3

more potent = slower speed of onset

Question 4

Depolarizing NMB agent examples

Answer 4

succinylcholine=short acting

• rapid onset (60-90s), rapid ester hydrolysis=short duration (8-12min)
• pseudocholinesterase deficiency = much longer half life

Question 5

Non-depolarizing NMB agents

Answer 5

-Pancuronium = long acting
-Roncuronium, Atracurium, cisatracurium = intermediate acting
Mivacurium = short acting (but not used because unreliable)

Question 6

succinylcholine pharmodynamins (3 mech, 3 sites)

Answer 6

mech: nAChR agonism, Na+ channel inactivation, nAChR desensitizaion
sites: postsynaptic (MAIN), presynaptic and extrajunctional nAChR

Question 7

side effects of succinylcholine at postsynaptic nAChR

Answer 7

• hyperkalemia (if pre-existing hyperkalemia then deadly, normally ok): caused my channels opening
• muscle contraction (warning sign of MH)
• extraoccular muscle contraction raises intraoccular P

Question 8

side effects of succinylcholine at presynaptic nAChR

Answer 8

• muscle fasciculations: damage, increased O2 consumption/ CO2 production. (note CO2 increases intracranial P), Catecholamine release (HR and BP up), raised intragastic P
• *small defasiciulating dose of nondepolarizer may prevent

Question 9

side effects of succinylcholine at extrajuctional nAChR

Answer 9

• severe K+ increase –> cardiac arrest
• note: normally expn of R suppressed by neural activity, but denervation, burns, lesions, severe trauma or muscular dystrophy may increase numbers

Question 10

Miscellaneous side effects (not at 3 main sites) of succinylcholine

Answer 10

• trigger for MH
• rhabdomolysis
• bradycardia via vagus nerve

Question 11

NMB uses

Answer 11

• facilitate intubation, mechanical intubation
• reduce anesthetic requirements’
• create idea surgery conditions + prevent mvmt
• **No analgesic/hypnotic properties!!

Question 12

reversal of NMB

Answer 12

• depolarizing = have to wait it out!!
• non-depolarizing: give AChE inhibitor to increase endogenous ACh (reversible antagonists)

aside: steroids: suggamadex? soon?

Question 13

side effects of non-depolarizing agents

Answer 13

-cardio: bradycardia/sinus arrest
-pulmonary: broncospasm, increased bronchial secretions
-cerebral mAChR
“cholerginc side effects”

Question 14

BASIC mechanism difference btw depolarizing and non-depolarizing muscle agents

Answer 14

• Depol: nAChR agonist

- non-depol: nAChR competitive antagonist