Muscular Dystrophy Flashcards
What is the pathophysiology of Duchenne’s muscular
dystrophy?
Patients with Duchenne’s muscular dystrophy produce an
abnormal protein called dystrophin that is found near the
sarcolemma of muscle cells.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 752-753.
What are the physical signs and symptoms of
Duchenne’s muscular dystrophy?
The initial signs of Duchenne’s muscular dystrophy are related
to weakness in the proximal skeletal muscle groups and
manifest as an alteration in gait, difficulty climbing stairs, and
frequent falls. The progressive and symmetric deterioration in
muscle strength is associated with fatty infiltration of the
muscles which results in pseudohypertrophy of the muscles.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 444-445.
What is the incidence of Duchenne’s muscular
dystrophy and what patient demographic does it
affect?
Duchenne’s muscular dystrophy occurs in 3 out of every 10,000
live male births. It is an X-linked recessive disorder that
presents most commonly in children between the ages of 3 and
5 years. By age 12, most patients are confined to a wheelchair.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 752.
What is the most common form of muscular
dystrophy?
Duchenne’s muscular dystrophy is the most common and most
severe form of dystrophy.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 445.
What is the most common cause of death in patients
with Duchenne’s muscular dystrophy?
Death is most often attributed to pneumonia, respiratory failure,
or cardiac failure and usually occurs between the ages of 15
and 25.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 753.
What lab value is typically elevated in patients with
Duchenne’s muscular dystrophy?
Because the skeletal muscle cells are prone to necrosis, serum
creatine kinase levels may be 20 to 100 times higher than
normal.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 445.
What are the cardiac signs of Duchenne’s muscular
dystrophy?
Cardiac muscle is not spared in Duchenne’s muscular
dystrophy. The degeneration of myocardial cells results in a
short PR interval, tall R waves in V1, deep Q waves in the limb
leads, and sinus tachycardia. Papillary muscle dysfunction and
decreased myocardial contractility can lead to mitral
regurgitation and congestive heart failure.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 445.
What are the respiratory complications of
Duchenne’s muscular dystrophy?
Progressive respiratory muscle weakness predisposes the
patient to respiratory insufficiency and recurrent pneumonia.
Sleep apnea often develops and can result in pulmonary
hypertension and the development of kyphoscoliosis contributes
to the already compromised respiratory state.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 445.
What are the general anesthetic implications of
Duchenne’s muscular dystrophy?
Gastric hypomotility and decreased laryngeal reflexes
predispose the patient to pulmonary aspiration. Succinylcholine
is contraindicated due to the risk for rhabdomyolysis,
hyperkalemia, and cardiac arrest. They have an increased risk
for malignant hyperthermia, so regional anesthesia is preferred,
but if a general anesthetic is undertaken, careful monitoring of
capnography and temperature should be performed with
dantrolene readily available. The risk for postoperative
pulmonary complications is high due to skeletal muscle
weakness.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 445.
How does the patient with Duchenne’s muscular
dystrophy respond to succinylcholine and
nondepolarizing muscle relaxants?
Because of the risk of rhabdomyolysis, hyperkalemia, and risk
of cardiac arrest, succinylcholine is contraindicated in patients
with Duchenne’s muscular dystrophy. Also, the risk of
malignant hyperthermia is increased in these patients and
general anesthesia is typically avoided. The response to
NDMRs is normal.
Hines RL, Marschall KE. Anesthesia & Co-Existing Diseases.
6th ed. Philadelphia, PA: Elsevier-Saunders; 2012: 445
What events would be most likely to induce myotonic
contractions in a patient with myotonic dystrophy
In patients with myotonic dystrophy, myotonic contractions can
be so severe that ventilation can become difficult. Agents that
are associated with an increased risk of producing myotonic
contractions include succinylcholine, neostigmine, and
physostigmine. Shivering associated with inhalation anesthesia
can also induce myotonic contractions (small doses of
meperidine can be administered to prevent this). The response
to nondepolarizing muscle relaxants appears to be normal, but
shorter-duration agents such as cisatracurium are
recommended. Reversal of NDMRs is not recommended. If
myotonic contractions become severe, they can be treated with
the injection of procaine directly into the muscle or by
administering 300-600 mg of quinine hydrochloride
intravenously. Regional anesthesia is not contraindicated, but
does not necessarily relieve myotonic contractions.
Butterworth JF, Mackey DC, Wasnick JD. Morgan & Mikhail’s
Clinical Anesthesiology. 5th ed. New York, NY: McGraw-Hill;
2013: 753.
