Muscle Relaxants

Question 1

Succinylcholine:
Dose, onset, duration

Answer 1

0.6-1.5mg/kg
Less than 1 minute
5 to 10 mins

Question 2

Succinylcholine phases

Answer 2

• 1 - depolarization with fasciculations
• 2 - repolarization - dose exceeds 2-4mg/kg
  Potassium goes up 0.5mEq/L

Question 3

Succinylcholine metabolism

Answer 3

Pseudocholinesterase

Can be affected by liver disease, anticholinesterases, chemotherapeutic drugs

Atypical plasma cholinesterase can not hydrolyze succinylcholine

Only discovered when more than 1 hour of skeletal muscle paralysis occurs

Question 4

DMR Side effects

Answer 4

Cardiac dysrhythmias
Hyperkalemia
Myalgia
Myoglobinuria
Increased intraocular, intragastric, intracranial pressure
Trismus

Use atropine to decrease the cardiac effects

Question 5

NDMR Classification:

Answer 5

Long - d-tubocurarine, metocurine, gallamine, pancuronium, pipecuronium, doxacurium - 3 to 5 - 60 to 90

Intermediate - atracurium, vecuronium, rocuronium

Short - mivacurium

Question 6

Mivacurium:

Answer 6

6 to 16 min
Plasma cholinesterase
Some histamine release ,- avoid in asthma

Question 7

Why is pancuronium unique?

Answer 7

Increases HR, BP

Question 8

Enhance NDMR effect:

Answer 8

VA, aminoglycosides, magnesium, local anesthetics, cardiac antiarrhythmics, calcium blockers

Hypothermia

Reduced pH

Hypokalemia

Question 9

How to antagonize NMDR?

Answer 9

Anticholiesterases like neostigmine, pyridostigmine

Question 10

Suggamadex:

Answer 10

Reverses NM blockade

Question 11

Suggamadex contraindication:

Answer 11

Renal disease

Question 12

Malignant hyperthermia diagnosis:

Answer 12

Muscle biopsy using the in vitro contracture test:
- femoral nerve block
- remove 8-10 muscle speciments (3-4cm long) from the vastus medialis muscle
- Positive diagnosis if the muscle contracts in response to caffeine or halothane

Question 13

Signs of malignant hyperthermia:

Answer 13

• Sustained jaw rigidity
• Unexplained tachycardia w/ an unexpected rise in ETCO2 or minute volume
• Falling SaO2 despite increased FiO2
• CVS instability
• Generalized rigidity
• Core temperature rise of 2C per hour

Question 14

How to manage a patient with a history of malignant hyperthermia?

Answer 14

• Avoid succinylcholine and volatile anesthetics
• Baseline core temperature and measuring of core temperature
• Dantrolene should be handy

Question 15

One of the more serious effects of succinylcholine is ___________
This effect can be reduced by administration with _______

Answer 15

Cardiac dysrhythmias
Atropine

Question 16

Effects of succinylcholine

Answer 16

Cardiac dyr
INhythmias
Hyperkalemia
Myoglobinuria
Increased intraocular pressure
Increased intragastric pressure
Increased intracranial pressure
Trismus (especially in pediatrics)

Question 17

Pharmacokinetics of NDMR’s:

Answer 17

• Highly ionized and possess limited lipid solubility
• Can not easily pass lipid membranes
• Do not produce CNS effects
• Renal tubular reabsorption is minimum
• Oral administration is not effective
• Maternal administration does not affect the fetus

Question 18

Long-acting NDMR doses:

Answer 18

D-Tubocurarine - 0.51 mg/kg
Metocurine - 0.28mg/kg
Gallamine 1.0mg/kg
Pancuronium - 0.07mg/kg
Pipecuronium - 0.07mg/kg
Doxacurium - 0.25-0.40mg/kg

Question 19

Intermediate-acting NMDR doses:

Answer 19

Atracurium - 0.3-0.6mg/kg
Cisatracurium - 150ug/kg
Vecuronium 80-100ug/kg
Rocuronium - 0.6-1.0mg/kg

Question 20

Mivacurium dose, kinetics

Answer 20

Intubation - 0.07-0.25mg/kg
Infusion- 0.4-0.6mg/kg/h

6-16mins
Some histamine release, avoid in asthma

Question 21

Factors enhancing NDMR effects:

Answer 21

• Drugs - VA’s, AG AB’s, Mg, local anesthetics, antiarrhythmics, CCB’s
• Hypothermia
• Reduced pH
• Hypokalemia

Question 22

Test to determine fi there is no significant NM block:

Answer 22

• Head lift

Question 23

Anticholinesterases like _______ can cause _____ this can be prevented with use of _________

Answer 23

neostigmine
pyridostigmine
bradycardia
atropine

Question 24

Suggamadex use and contraindication

Answer 24

Reversal of NM blockade by NDMR
Do not use with renal disease

Question 25

In vitro contracture test:
Performed under ______
8-10 segments about 3-4cm long are removed from the __________
Diagnosis is considred positive if the muscle contracts in response to________

Answer 25

Femoral nerve block
Vastus medialis muscle
Caffeine or halothane

Question 26

Signs of MH:

Answer 26

• Muscle rigidity
• Jaw rigidity
• Unexpected tachycardia w/ unexpected rise in ETCO2
• Falling SaO2 but increase in FiO2
• Cardiovascular instability
• Generalized rigidity
• Core temperature rises 2C per hour

Question 27

A patient is experiencing symptoms of MH during surgery, what do we do?

Answer 27

Stop giving the causative medication
Give 100% oxygen
Give dantrolene 1mg/kg - usually require 2.4mg/kg, up to 10mg/kg can be used
Reduce core temperature with cold fluid IV
Correct acidosis and hyperkalemia