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21 Cards in this Set
- Front
- Back
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What is the cause of myasthenia gravis?
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decreased available acetylcholine receptors on the postsynaptic site on the NMJ due to destruction by circulating antibodies
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What are some of the hallmark findings in myasthenia gravis?
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muscle weakness w/
1. respiratory insufficiency, 2. aspiration, 3. cardiomyopathy 4. cardiac failure |
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How is muscle weakness manifested in myasthenia gravis?
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1. ptosis,
2. diplopia, 3. dysphagia, 4. increased risk of respiratory failure and aspiration, 5. cardiomyopathy, (smooth muscle is not affected) |
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What are the types of myasthenia gravis?
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-type 1: limited to extraocular muscles
-type 2a: mild form with respiratory muscles spared -type 2b: more rapidly progressive with involvement of respiratory muscles -type 3: acute onset, rapid progression, high mortality -type 4: severe form resulting from progression of 1 or 2 |
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what conditions are consistent with cholinergic crisis?
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SLUDE + BBC
Salivation, Lacrimation, Urination, Defecation, Erection Bradycardia Bronchoconstriction Ciliary constriction |
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How is cholinergic crisis treated?
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maintain oxygenation and ventilation, and atropine 2mg should be given
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How is myasthenic crisis treated?
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maintain oxygenation and ventilation and give neostigmine
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What is the tensilon test used for?
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distinguish myasthenic from cholinergic crisis
-tensilon/edrophonium is a very short acting anticholinesterase that inhibits acetycholinesterase which normally breaks downacetycholine and results in the buildup of Ach at the NMJ -if weakness is from myasthenic crisis strength improves -if weakness is from cholinergic crisis symtoms will worsen |
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What tests should you get preop in a patient with suspected myasthenia?
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ABG and PFTs,
-consider tensilon test to distinguish myasthenic from cholinergic crisis |
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What preop sedation should you give a patient with myasthenia gravis?
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typically no preop sedation is required
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What should you inform patients with myasthenia gravis about prior to general anesthesia?
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possible need for prolonged mechanical ventilation postop
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How should you change your doses of neuromuscular blockers in myasthenia gravis patients?
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-possible resistance to SCh (less receptors to cause muscle stimulation),
-decreased dose of nondepolarizer (1/5 normal dose) |
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When do patients with myasthenia gravis get a thymectomy?
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drug resistant disease
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What different should you do in pregnant patients with myasthenia gravis in labor?
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continue anticholinesterase medications during labor, use great caution when giving sedatives
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How are neonates of mothers with myasthenia gravis affected?
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-neonatal myasthenia gravis is present in 20-30% of newborns,
-generalized weakness is most important manifestation, -anticholinesterase therapy is generally needed for 3-4 weeks, -higher risk of developing respiratory therapy |
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What is the mechanism of myasthenia syndrome (lambert-eaton)
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decreased acetylcholine release following nerve stimulation
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How are patients with myasthenic syndrome affected by NMBDs
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-marked sensitivity to both depolarizers (decreased ACh leads to increased sites for SCh to bind) and nondepolarizers (decreased ACh leads to more competitive inhibition from nondepolarizers)
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How is myasthenic syndrome affected by removal of bronchial cancer?
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temporary but not permanent improvement
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What are the manifestations of myasthenic syndrome?
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1. muscular weakness, associated with bronchial carcinomas,
2. increased muscle strength with exercise, 3. no improvement following administration of anticholinesterases, 4. involves proximal muscles of the limbs and not the bulbar muscles 5. may occur in pts with thyroid disease and SLE |
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In the myasthenic pt, what can precipitate a crisis?
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1. inadequate pyridostigmine
2. steroid muscle relaxant 3. excessive neostigmine 4. intubating dose o succinylcholine |
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What are the anticholinesterase drugs used in myasthenia gravis? What is the difference between the 2?
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1. pyridostigmine - lasts longer and produces fewer muscarinic side effects; PO = 60 mg, IM or IV = 2 mg
2. neostigmine 3. phospholine iodide - extremely potent, reserved for pts with severe myasthenia |
