Skeletal neuromuscular blockers

Question 1

what do skeletal NM blockers do?

Answer 1

produce profound skeletal muscle relaxation useful for many medical purposes

• an on NM receptors
• block nicotinic receptors in muscles

Question 2

first NM blocker

Answer 2

curare

-put in bamboo tubes-> tubocurarine

Question 3

medical use of NM blockers

Answer 3

surgery (especially abd/eye), min anesthetic needed

Orthopedic procedures: overcome muscle spasms which can sometimes occur in compound fractures

Bronchoscopy, laryngoscopy
-done under general anesthesia, blockers overcome gag reflex

Question 4

electroshock therapy

Answer 4

NM blockers in electroshock to treat severe depression

-eliminate possible injury during convulsive episode

Question 5

NM blockers in artificial respiration

Answer 5

• eliminates any respiratory drive which would interfere with artificial rhythm
• infants and elderly

Question 6

two types of NM blockers

Answer 6

1. Competitive -> curare type
   - newborn and myasthenics sensitive
   - reversed by neostigmine
2. Non-competitive
   - succinylcholine
   - new born and myasthenics resistant
   - NOT REVERSED by neostigmine (initially)
   - cause a depolarizing block at first but then block becomes “curare like”
   - associated with transient muscle twitch and postoperative muscle soreness

Question 7

monitoring NM blockers

Answer 7

transderm. electrical stimulation of hands or face
- Train of Four (TOF) impulses
- response of 4th twitch relative to 1st is TOF ration

Question 8

when does the fade occur

Answer 8

non-depolarizing block

• recovery to .7 needed for spontaneous ventilation
• .9 for full clinical recovery

Question 9

when is there no fade

Answer 9

depolarizing block

-can occur with phase II block with succinylcholine

Question 10

curare type drugs

Answer 10

d-tubocurarine

mivacurium

Question 11

d-tubocurarine

Answer 11

excreted in urine

• 50 mins
• blocks histamine release
• is a ganglionic block

Question 12

mivacurium

Answer 12

hydrolysis-> spontaneous and plasma esterases

• 15 min duration
• blocks little histamine release
• NOT a ganglionic blocker

Question 13

succinylcholine

Answer 13

lasts about 4 mins

• two molecules of acetylcholine stuck together
• hydrolysed by pseudocholinesterase

Question 14

sequence of muscle paralysis by curare

Answer 14

muscle of eye, speech first-> then eyelids-> then fingers/toes-> then limbs become heavy-> then intercostal affected-> lastly the diaphragm

• arms, legs, neck first
• face not affected much initially
• respiration last

Question 15

precautions for neuromuscular blockers

Answer 15

• always given IV or IM
• much individual variation in response
• apparatus for artificial respiration must be available
• some drugs increase the effects (some antibiotics, streptomycin, general anesthetics, enflurane)
• succinylcholine hydrolysed to choline which stimulates ganglia-> increase BP
• succinylcholine muscarinic effect, bradycardia
• succinylcholine and malignant hyperthermia-> especially with halothane, isoflurane
• involves congential myopathy-> defective ryanodyne receptor-> excess Ca release in muscle
• use dantrolene