Neuromuscular Blockers

Question 1

Where is the best place to measure onset of blockade?

Answer 1

• muscle = orbicularis occult (closes lid) or corrugator supercilii (eyebrow twitch)
• nerve = facial nerve

Question 2

Where is the best place to measure recovery of blockade?

Answer 2

• muscle = adductor pollicis (thumb adduction) or flexor hallicus (big toe flexion)
• nerve = ulnar nerve or post tibial nerve

Question 3

How does succs cause bradycardia?

Answer 3

stimulates the M2 receptor on the SA node

Question 4

Does succs cause tachycardia?

Answer 4

• yes
• it mimics action Ach at the sympathetic ganglia
• can cause tachycardia and HTN
• causes tachycardia in adults more than bradycardia

Question 5

How does succs affect intraocular pressure?

Answer 5

it increases intraocular pressure by 5-15 mmHg for up to 15 min.

Question 6

How does succs affect intracranial pressure?

Answer 6

• it temporarily increases intracranial pressure

- minimized or prevented by a defasciculating dose

Question 7

How does succs affect intragastric pressure?

Answer 7

• causes contraction of abdominal contents
• increases lower esophageal sphincter tone
• these 2 cancel each other out and therefore the pressure is unchanged

Question 8

Do you cancel the case if the pt has a masseter spasm after succs?

Answer 8

• No, not if it happens in the absence of other s/sx of MH

- succs is a trigger of MH

Question 9

What metabolizes acetylcholine?

Answer 9

• Type 1 cholinesterase
• Acetylcholinesterase
• True cholinesterase
• Specific cholinesterase
• Genuine cholinesterase

Question 10

What metabolizes succs, mivacurium, and ester LAs?

Answer 10

• Type 2 cholinesterase
• Butyrylcholinesterase
• False cholinesterase
• Plasma cholinesterase
• Pseudocholinesterase

Question 11

What are drugs that reduce Pseudocholinesterase activity?

Answer 11

• Metoclopramide
• Esmolol
• Neostigmine (NOT edrophonium)
• Echothiophate
• Oral contraceptives / estrogen
• Cyclophosphamide
• Monoamine Oxidase Inhibitors
• Nitrogen mustard

Question 12

What are co-existing conditions that reduce Pseudocholinesterase activity?

Answer 12

• Atypical PChE
• Severe liver disease
• Chronic renal disease
• Organophosphate poisoning
• Burns
• Neoplasm
• Advanced age
• Malnutrition
• Pregnancy (late stage)

Question 13

Who is at risk for post-op myalgia with Succs?

Answer 13

• young adults undergoing adulatory surgery (women > men)

- those who do not engage in routine strenuous activity

Question 14

How can post-op myalgia from Succs be reduced?

Answer 14

• it may be reduced by pretreatment with a NDNMB
• on tenth of the ED95 of a NDNMB can reduce fasciculations
• should be administered 3-5 min before succs

Question 15

What is Hoffman Elimination dependent upon?

Answer 15

• normal blood pH and temperature
• rxn is faster w/ alkalosis and hyperthermia
• rxn is slower w/ acidosis and hypothermia

Question 16

Does mivacurium produce an active metabolite?

Answer 16

No

Question 17

What drugs potentiate NMBs?

Answer 17

• volatile anesthetics (Des>Sevo>Iso>N2O>Propofol)
• Antibiotics (Aminoglycosides, Polymyxins, Clindamycin, Lincomycin, Tetracycline)
• Antidysrhythmics (verapamil, amlodipine, lidocaine, quinidine)
• local anesthetics (probably all of them)
• Diuretics (furosemide)
• dantrolene, cyclosporine, tamoxifen

Question 18

What electrolyte imbalances potentiate NMBs?

Answer 18

• inc lithium (activates K+ channels)
• inc Mg (dec Ach release from presynaptic nerve)
• dec Ca+2 (dec Ach release from presynaptic nerve)
• dec K+ (dec resting membrane potential)

Question 19

What patient factors potentiate NMBs?

Answer 19

• hypothermia (dec metabolism and clearance)

- women (women are more sensitive to the effects of NMBs compared to men)

Question 20

A patient with what type of condition should not receive pancuronium?

Answer 20

• hypertrophic cardiomyopathy

Question 21

What is the order of highest to lowest likelihood of NMBs that produce anaphylaxis?

Answer 21

succs > atracurium > cisatracurium > rocuronium > vec