Neuromuscular Blocking Agents (Barash Ch 11)

Question 1

Only depolarizing NMBA

Answer 1

Succinylcholine

Question 2

Succinylcholine side effects

Answer 2

• Bradycardia and asystole
• Fasciculations (80-90%) pretreat with non-depol to prevent
• Myalgias (50-60%) prevent with NSAID pretreatment
• Increased ICP (not as bad as DL with light sedation) and IOP
• Hyperkalemia (0.5 mEq/L), avoid in kids burns, paraplegics, infection, sepsis, etc

Question 3

What drug is responsible for more anaphylactic reactions than any other anesthetic drug (1 in 10,000)?

Answer 3

Succinylcholine

Question 4

Clinical indications for succinylcholine

Answer 4

Biggest is RSI

Question 5

Succinylcholine dosing for RSI, adults and kids…

Answer 5

Adults: 1.0 mg/kg, children: 1.5-2.0 mg/kg (kids more resistant)

Question 6

Contraindications for succinylcholine

Answer 6

• Pseudocholinesterase deficiency
• History of malignant hyperthermia (SCh + inhaled anesthetic = 20x risk)
• Critical care patients, immobilized patients, paraplegic pts, acidotic and hypovolemic patients (those at risk for lethal hyperkalemia)
• NOTE: renal failure is not a contraindication if K+ is normal

Question 7

Benzylisoquinolinium non-depolarizing NMBAs

Answer 7

Atracurium, cisatricurium, mivacurium

Question 8

Aminosteroid non-depolarizing NMBAs

Answer 8

pancuronium, vecuronium, rocuronium

Question 9

Dosing change of non-depolarizing NMBAs in hypervolemic state, why

Answer 9

Increase the dose initially. Due to positive charge the are distributed in ECF meaning lower concentrations will be present.

Question 10

Pancuronium, short or long acting?

Answer 10

Long (1-2 hours), not used much any more because of potential for residual post-operative neuromuscular weakness.
- Accumulates due to active metabolite (50% potency of parent drug)

Question 11

Vecuronium, duration of action?

Answer 11

• Intermediate duration, no CV effects
• More potent than rocuronium, thus slower onset
• Metabolite has 60% potency of parent drug so can accumulate similar to pancuronium

Question 12

Redeeming properties of Rocuronium?

Answer 12

Low potency means high plasma to active site gradient and quick onset. Given rapid onset and very few allergic reactions as well as lack of CV side effects it is now a good choice for RSI.

Question 13

Rocuronium is used in high doses 1.0-1.2 mg/kg for RSI, what are some things to be aware of when giving Rocuronium at high doses?

Answer 13

• Onset is fast ~60 seconds but is quite variable so may have difficult intubating conditions due to incomplete effect at 60 sec.
• Duration is long at high doses >1 hr

Question 14

What is suggammadex and why is it important?

Answer 14

Drug that forms complex with NMBA, reducing binding availability to nicotinic receptors. Can Give after Rocuronium if a failed RSI to decrease the duration of paralysis.

Question 15

Why is atracurium not optimal for induction/intubation?

Answer 15

At high doses it causes histamine release causing skin flushing, tachycardia, and hypotension.

Question 16

Why was CIS-atracurium developed?

Answer 16

To decrease the propensity for histamine release

Question 17

Cisatracurium’s positive qualities?

Answer 17

• intermediate duration
• no renal clearance
• higher potency than atracurium so lower doses mean no histamine release

Question 18

What affect does propofol have on NMBAs? And local anesthetics?

Answer 18

• Propofol has no effect on NMBAs

- Local causes increased duration (minimal) but no change to onset time