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Lesson 36. Myasthenia Gravis

2-36. MYASTHENIA GRAVIS

a. Definition. Myasthenia Gravis is an autoimmune disorder affecting the neuromuscular transmission of impulses in the voluntary muscles of the body. In normal individuals, transmission of impulses from the nerve to the motor end plate of the muscle is accomplished by the transmitter substance acetylcholine.

(1) Acetylcholine is released at the nerve ending and moves to the muscle end plate, causing muscle contraction.

(2) Acetylcholine is then broken down into acetate and choline by the substance cholinesterase.

(3) In myasthenia gravis, one of three physiological abnormalities may exist:

(a) There may be too much cholinesterase present, and acetylcholine is destroyed too quickly.

 (b) There may be too little acetylcholine released from the nerve fiber, resulting in inadequate depolarization of the motor end plate.

(c) The motor end plate is not sensitive to the action of acetylcholine.

b.     Signs and Symptoms.

(1) Diplopia (double vision).

(2) Ptosis (dropping of one or both eyelids).

(3) Abnormal muscle weakness; characteristically worse after effort and improved by rest.

(4) Sleepy, mask-like facial expression with difficulty smiling.

(5) Speech weakness (high-pitched nasal voice).

(6) Difficulty swallowing.

(7) Choking, aspiration of food.

c.      Medical and Nursing Management.

(1) Primary drug therapy (anticholinesterase drugs to enhance the action of acetylcholine at the myoneural junction).

(a) Drug must be given exactly on time to control symptoms.

(b) After initial medication adjustments are made, patient learns to take his medication according to his/her needs.

(2) Patient needs explicit instructions regarding medications.

Actions.

Reasons for timing.

Dosage adjustment.

Symptoms of overdosage and actions to take should crisis occur.

(d)

(3) Have mealtimes coincide with peak effect of anticholinergics, when ability to swallow is best.

(4) Obtain medic alert bracelet signifying that patient has myasthenia gravis.

 

(5) Wear an eyepatch over one eye (alternating from side to side) if diplopia occurs.

(6) Control factors which lead to fatigue.

(7) Emphasize importance of avoiding contact with individuals with colds or respiratory infections, since these conditions could be devastating to the myasthenic patient.

(8) Instruct patient to inform dentist of myasthenia condition since Novocaine is usually poorly tolerated.

(9) Instruct patient to rest at frequent intervals and avoid fatigue. d. Management of the Crises of Myasthenia.

(1) Myasthenic crisis may result from natural deterioration of the disease, emotional upset, upper respiratory infection, surgery, or steroid therapy.

(2) Patient may be temporarily resistant to anticholinesterase drugs or need increased dosage.

(3) Cholinergic crisis may result from overmedication with anticholinergic drugs.

(4) Patient must be placed in an intensive care unit for continuous monitoring of the patient's respiratory status.

(5) Provide ventilatory assistance, endotracheal intubation, mechanical ventilation, if required.

(6) Administer appropriate medications, as determined by patient's status and cause of the crisis.

(7) Support patient's fluid and nutritional needs, as ordered and indicated by patient's condition.

(8) Give continued psychological support during crisis period, as patient is still alert.

David L. Heiserman, Editor

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Revised: June 06, 2015