Myasthenia gravis

Overview

Acquired autoimmune disorder characterized by abnormal fatigability of striated (skeletal) muscles; most commonly the extraocular, pharyngeal, facial, and respiratory muscles Sporadic but progressive weakness Muscle weakness exacerbated by exercise and repetitive movement Initial symptoms related to cranial nerves Possibly life-threatening if there's respiratory system involvement Spontaneous remissions occurring in about 25% of patients Two forms: ocular (weakness limited to eyelids and extraocular muscles) and generalized (ocular weakness in conjunction with variable bulbar, proximal limb, and respiratory muscle involvement) Onset typically mild and intermittent occurring over several years; possible sudden and severe onset

Nursing Considerations-Nursing Diagnoses

Activity intolerance Anxiety Bathing self-care deficit Chronic low self-esteem Disturbed body image Dressing self-care deficit Fatigue Feeding self-care deficit Impaired gas exchange Impaired physical mobility Ineffective airway clearance Risk for aspiration

Diagnostic Test Results-Laboratory

Anti-acetylcholine receptor (AchR) antibody is positive in 80% to 90% of patients with myasthenia gravis. Antistriated muscle (anti-Sm) antibody is present. Muscle specific tyrosine kinase (MuSK) antibody present in about 40% to 50% of patients with generalized myasthenia gravis; is negative in patients with ocular myasthenia gravis.

Treatment-Medications

Anticholinesterase agents such as oral pyridostigmine bromide or subcutaneous neostigmine as first-line agents Corticosteroids such as predniSONE I.V. immune globulin Mycophenolate mofetil, azathioprine, cyclophosphamide, or cycloSPORINE as second-line agents

Treatment-Diet

As tolerated Thickened liquids if dysphagia a problem

Treatment-Activity

As tolerated (exercise and application of heat possibly worsening symptoms; planned rest periods possibly slowing symptoms)

Overview-Pathophysiology

Blood cells and thymus gland produce antibodies that block, destroy, or weaken neuroreceptors (which transmit nerve impulses); primarily acetylcholine; antibodies are present in 80% to 90% of people with myasthenia gravis. The number of acetylcholine receptors in the postsynaptic muscle membrane is decreased. The result is failure in transmission of nerve impulses at the neuromuscular junction.

Diagnostic Test Results-Imaging

Chest X-rays or computed tomography scan results show thymoma.

Nursing Considerations-Nursing Interventions

Ensure a patent airway; be alert for myasthenic crisis as evidenced by increasing respiratory distress and respiratory failure. Have emergency respiratory equipment readily available at the bedside. Provide psychological support; encourage the patient and his family to verbalize their concerns and feelings; allow time for them to ask questions. Provide frequent rest periods; encourage the patient to perform activities earlier in the day when strength is greatest; cluster nursing activities to provide for rest periods. Maintain nutritional management program; encourage the patient to consume nutrient dense foods; encourage the patient to chew slowly and to note changes in his ability to chew; enlist the aid of the dietitian to assist with meal planning; encourage the use of thickened liquids if the patient has difficulty swallowing. Arrange for speech therapy to assist with swallowing if appropriate Encourage the patient to participate in self-care activities to extent possible; provide positive reinforcement. Maintain socialization. Give prescribed drugs; administer pyridostigmine bromide orally or neostigmine subcutaneously. Prepare the patient and his family for possible thymectomy.

Nursing Considerations-Associated Nursing Procedures

Fall prevention IV bag preparation IV bolus injection IV catheter insertion IV pump use Impaired swallowing and aspiration precautions Neurologic assessment Oral drug administration Oxygen administration Pain management Protective environment (PE) guidelines Pulse assessment Pulse oximetry Respiration assessment Venipuncture

Overview-Causes

Idiopathic Autoimmune disorder associated with the thymus gland Other immune and thyroid disorders causing secondary symptoms Rheumatoid arthritis Systemic lupus erythematosus Thyrotoxicosis

Nursing Considerations-Monitoring

Muscle involvement and severity of weakness Neurologic function Respiratory status Airway Chewing and swallowing ability Response to medications

Overview-Incidence

Myasthenia gravis occurs at any age. Males and females are affected equally; incidence in females peaks around ages 30 to 39; incidence in males peaks around ages 60 to 79.

Treatment-General

Plasmapheresis Emergency airway and ventilation management

Patient Teaching-Discharge Planning

Refer the patient to the Myasthenia Gravis Foundation. Refer the patient to social services as appropriate for assistance with chronic condition.

Overview-Complications

Respiratory distress Acute respiratory arrest Atelectasis Pneumonia Dysphagia Aspiration Myasthenic crisis Cholinergic crisis

Diagnostic Test Results-Other

Results of edrophonium or Tensilon test are positive, showing temporary improved muscle function and confirming the diagnosis. Ice pack test (for patients in whom Tensilon test is contraindicated) reveals decreased ptosis after ice applied for 60 seconds to closed eyelid. Electromyography results show a rapid reduction of more than 10% in the amplitude of evoked responses. Repetitive nerve stimulation tests reveal a decremental response to stimuli.

Assessment-Physical Findings

Sleepy, masklike expression; myasthenic sneer (rise of mid-lip without movement of corners of mouth) Drooping jaw Ptosis; worsening with propping of opposite eyelid or with sustained upward gaze Decreased breath sounds Decreased tidal volume Nasal tone of voice Respiratory distress and myasthenic crisis Diplopia Difficulty swallowing or chewing Limb weakness (more commonly upper limb than lower limb)

Treatment-Surgery

Thymectomy

Assessment-History

Varying assessment findings Progressive muscle weakness Extreme muscle weakness and fatigue (cardinal symptoms) Ptosis and diplopia (the most common sign and symptom) Difficulty chewing and swallowing Jaw hanging open (especially when tired) Head bobbing Symptoms that are milder on awakening and worsen as the day progresses Short rest periods that temporarily restore muscle function Symptoms that intensify before the menstrual period, during pregnancy, after emotional stress, after prolonged exposure to sunlight or cold, and with infections

Patient Teaching-General

disorder, diagnosis, and treatment, including possible underlying cause and medications for treatment that early in disease symptoms are transient with asymptomatic periods lasting for days or weeks; with progression, asymptomatic periods lessen or are lost entirely with symptoms fluctuating from mild to severe that many patients experience sustained remissions preoperative and postoperative care measures including what to expect after surgery energy-conservation techniques prescribed medication, including drug name, dosage, frequency, and route of administration and duration of therapy signs and symptoms of adverse effects need to avoid strenuous exercise, stress, infection, and unnecessary exposure to the sun or cold weather nutritional management program swallowing therapy program danger signs and symptoms, especially those of myasthenic crisis and cholinergic crisis and the need to report any to the practitioner immediately.

Nursing Considerations-Expected Outcomes

perform activities of daily living within the confines of the disease process identify strategies to reduce anxiety perform bathing activities to the fullest extent possible voice feelings related to increased self-esteem express positive feelings about body image perform dressing activities to the fullest extent possible verbalize the importance of balancing activity with adequate rest periods perform self-care needs related to feeding to the fullest extent possible maintain adequate ventilation and oxygenation maintain range of motion and joint mobility maintain a patent airway remain free from signs and symptoms of aspiration.