Exam 2 - Myasthenia Gravis

Question 1

myasthenia gravis

Answer 1

• autoimmune disease
• characterized by fluctuating weakness of certain muscle groups
• course: short-term remission, stabilization, severe progression

Question 2

risk factors of MG

Answer 2

• age 10 to 65 years
• women

Question 3

pathogenesis

Answer 3

• antibodies attach ACh receptors
• decrease in EACh receptor sites at the neuromuscular junction
• this prevents ACh molecules from attaching and stimulating muscle contraction

Question 4

clinical manifestations

Answer 4

• fluctuating weakness of skeletal muscle
• strength comes back after resting
• muscles involved: eyes/eyelids, facial, speaking, breathing

Question 5

myasthenic crisis

Answer 5

• acute exacerbation of muscle weakness
• triggered by a stressor: infection, surgery, emotional distress, pregnancy/menses, inadequate pharmacotherapy or other drugs
• major complication: breathing muscle weakness

Question 6

pharmacotherapy

Answer 6

• immunosuppressants (steroids)
• cholinesterase inhibitors

Question 7

how to cholinesterase inhibitors work

Answer 7

• prevent inactivation of Ash by cholinesterase
• intensify the effects of Ash released from motor neurons and increases muscle strength
• give 30-40 minutes prior to eating to strengthen swallowing muscles

Question 8

cholinesterase inhibitor

Answer 8

neostigmine

Question 9

neostigmine MOA

Answer 9

• enhances cholinergic action by facilitating transmission of impulses across neuromuscular junctions
• in therapeutic doses, this drug affects both muscarinic and nicotinic receptors

Question 10

cholinergic effects (neostigmine)

Answer 10

• GI: increased motility, diarrhea
• mouth: increased secretions
• bladder: urinary urgency
• heart: bradycardia
• lungs: bronchial constriction
• eyes: miosis (constriction)

Question 11

anticholinergic effects (atropine)

Answer 11

• GI: decreased motility, constipation
• mouth: dry mouth
• bladder: urinary retention
• heart: tachycardia
• lungs: bronchodilation
• eyes: mydriasis (dilation)

Question 12

neostigmine muscarinic adverse effects

Answer 12

• increased secretions, GI motility
• urinary urgency
• bradycardia
• bronchial constriction
• miosis, near-sightedness

Question 13

neostigmine neuromuscular (nicotinic) adverse effects

Answer 13

• therapeutic doses = increased muscle contraction
• toxic doses = reduced contraction
• toxicity can lead to cholinergic crisis

Question 14

cholinergic crisis

Answer 14

• extreme muscle weakness or paralysis
• s/s of excessive muscarinic stimulation
• always wear medic alert bracelet

Question 15

treatment of cholinergic crisis

Answer 15

• mechanical ventilation
• antidote for muscarinic sx: atropine

Question 16

MG crisis

Answer 16

• not enough stimulation or acetylcholine
• muscles are not stimulated and weak
• leads to respiratory failure

Question 17

cholinergic crisis

Answer 17

• too much acetylcholine or nystigmine
• overstimulation of muscles and muscles are worn out
• leads to respiratory failure

Question 18

how to differentiate between MG and cholinergic crisis

Answer 18

• give EDROPHONIUM: a short acting cholinesterase inhibitor and it temporarily increases acetylcholine

Question 19

what will happen in MG crisis after edrophonium

Answer 19

they will improve because there is an increase in acetylcholine

Question 20

what will happen in cholinergic crisis after edrophonium

Answer 20

they will worsen because they already have too much acetylcholine