Myasthenia Gravis Flashcards
What is myasthenia gravis?
Myasthenia gravis is an autoimmune disorder in which
acetylcholine receptors are destroyed or inactivated by
circulating antibodies at the neuromuscular junction.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 448.
Myasthenia gravis most often affects what patient
population?
Myasthenia gravis most often appears in females 20 to 30 years
old.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 448.
What other diseases and conditions have an
increased risk of occurrence in patients with
myasthenia gravis?
Hyperthyroidism is seen in about 10% of patients with
myasthenia gravis. There is also an increased risk for
rheumatoid arthritis, systemic lupus erythematosus, and
pernicious anemia.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 450.
What muscles are especially vulnerable to the
effects of myasthenia gravis?
Skeletal muscles innervated by the cranial nerves are the most
sensitive to the effects of myasthenia gravis. This manifests as
weakness in the ocular, pharyngeal, and laryngeal muscles. As
a result, ptosis, diplopia, and dysphagia are commonly seen as
the earliest symptoms of the disease.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 448.
What is the general response to exertion in patients
with myasthenia gravis?
Patients with myasthenia gravis often exhibit normal strength at
rest, but fatigue quickly with exertion.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 448.
What cardiac abnormality may be associated with
myasthenia gravis?
Myocarditis with atrial fibrillation is associated with myasthenia
gravis.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 450.
What are the principal treatment options for
myasthenia gravis?
The primary therapy is the administration of anticholinesterase
drugs, which enhance neuromuscular transmission.
Thymectomy, immunosuppressive agents, plasmapheresis, and
administration of immunoglobulin are other therapy options.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 450.
What are the indications for plasmapheresis in
patients with myasthenia gravis?
Plasmapheresis is usually reserved for patients with dysphagia
or oropharyngeal weakness as these symptoms place them at
greater risk for aspiration. Patients preparing to undergo
surgical procedures are also considered candidates for
plasmapheresis. Following plasmapheresis, patients with
myasthenia gravis often exhibit normal neuromuscular function.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 750.
What are the anesthetic implications regarding a
patient with myasthenia gravis?
Up to 80% of functional acetylcholine receptors can be lost,
resulting in skeletal muscle weakness, fatigue, and marked
sensitivity to nondepolarizing muscle relaxants.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 450-451.
What preoperative findings correlate with the need
for postoperative mechanical ventilation in patients
with myasthenia gravis undergoing thymectomy?
Because postoperative mechanical ventilation is common in
patients with myasthenia gravis, it is important to warn patients
preoperatively of the possibility. Factors associated with an
increased risk for postoperative ventilation following
thymectomy include: daily pyridostigmine dose greater than
750 mg, disease duration greater than 6 years, COPD, a peak
inspiratory pressure less than -25 cm H2O, and a vital capacity
less than 2.9 L.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 450.
What are the possible interactions with anesthesia
drugs in patients with myasthenia gravis who are
taking anticholinesterase medications?
Because these drugs inhibit plasma cholinesterase, they can
prolong the duration of action in drugs that are metabolized by
plasma cholinesterase. Two examples include ester local
anesthetics and succinylcholine.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 750-751.
How do patients with myasthenia gravis respond to
nondepolarizing muscle relaxants?
They are extremely sensitive to NDMRs and many clinicians
avoid the administration of these drugs whenever possible.
Defasciculating doses of NDMRs have been reported to
produce total paralysis in some patients. If an NDMR is
required, a shorter duration drug such as cisatracurium may be
the best choice.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 750-751.
If succinylcholine is required in the management of a
patient with myasthenia gravis, what pharmacologic
response can you expect to see?
The response of myasthenic patients to succinylcholine is
unpredictable, but commonly, a resistance is seen to the drug
(they may require 2 mg/kg) but the action of the drug will likely
be prolonged.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 750-751.
What antibiotic class is associated with an
aggravation of muscle weakness when administered
to patients with myasthenia gravis?
The administration of aminoglycoside antibiotics is associated
with aggravation of muscle weakness in myathenic patients.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 450.
