Nursing 4 Lecture 13 Myasthenia Gravis
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- Peak age at onset between 20 and 30
- Women affected 3X more often than men
- Chronic, sporadic, progressive
- -weakness, fatigue
- -has remissions and exacerbations
Occurs when the immune system makes antibodies that damage or block many of the muscles ACh receptors on the surface of muscle cells. This prohibits ACh from binding to the damaged receptors and acting on the muscle, which reduces muscle contractions, leading to weakness and fatigue.
Caused by a defect in the transmission of nerve impulses to muscles.
because the immune system which normally protects the body from foreign organisms, mistakenly attacks itself.
Onset is usually slow although some instances of fairly rapid development may be caused by infection, emotional upset, pregnancy or anesthesia.
Some patients have thymoma- most of the remaining cases show hyperplasia of the thymus.
-Ask if the patient has noticed rapid onset of fatigue, note reports of muscle weakness that increases on exertion or as day wears on and improves with rest
-Any history of ptosis (drooping eyelids), diplopia (double vision), or dysphagia and the type of diet best tolerated
Thymus Gland Tumor:
The thymus gland which lies in the upper chest area beneath the breastbone, plays an important role in the development of the immune system in early life. It cells from a part of the body's normal immune system. The gland is somewhat large in infants, grows gradually until puberty, and then gets smaller and is replaced by fat with age. In adults with myasthenia gravis, the thymus gland is abnormal. It contains certain clusters of immune cells indicatie of lymphoid hyperplasia- a condition usually found only in the spleen and lymphnodes during an active immune response. Some individuals with myasthenia gravis develop thymomas or tumors of the thymus gland. Generally thymomas are benign, but they can become malignant.
The relationshop between the thymus gland and myasthenia gravis is not yet fully understood. Scientists believe the thymus gland may give incorrect instructions to developing immune cells, ultimately resulting in autoimmunity and the production of the acetylcholine receptor antibodies, thereby setting the stage for the attack on neuromuscular transmission.
For most patients the muscles of facial expressions, chewing, and speech are affected
May need to assess nutritional intake and any recent weight loss- may have difficulty eating after talking, neck weakness may be mild or severe.
Because incidence is rare, dx may be delayed. MG may be immediatley confirmed by patients response to cholinergic drugs- thyroid function should be tested because thyrotoxicosis (excessive thyroid hormone) is present in a small number of MG pts.
Serum protein electrophoresis evaluates pt for immunologic disorders.
Testing for acetylcholine receptor antibodies- important diagnostic criterion becaues they are elevated in most pts with MG- positive results confirms the dx but negative does not rule out the disease.
- Tensilon testing is used most often for testing because its rapid onset and brief duration of action- differentiates with myasthenic crisis (too little cholinesterase inhibitor drugs) from cholinergic crisis (too much cholinesterase inhibitor drugs)
- *Has effect on respiratory and cardiac causing V-fib need atropine available
measures electrical potential of muscle cells- amplitude of moto units falls off with continued use. Muscle contractions decrease with each test reflecting fatigue.
- 2 Categories:
- -Affects the symptoms of MG without influencing the actual course of the disease
- -Therapeutic effort for inducing remission
Administration of immunosuppressive drugs of corticosteriods, plasmapheresis, and thymectomy
Not all patients have respiratory compromise
- -Ongoing assessment is a priority
- -Dysphagia may result which worsen respiratory problems, may be suctioning, chest PT, postural drainage
- -Mental status and emotional status
- -May need mechanical ventilation but BiPAP should be tried first in pts with acute respiratory failure form MG while awaiting IVIG therapy or plasma exchange
Interventions: Drug therapy
- 2 groups of drugs are typically prescribed for treatment of MG: anticholinesterase and immunosuppressants
- *give these meds on time to maintain blood levels and so will improve muscle strength
- Cholinesterase Inhibitor Drugs:
- -First line management of MG
- -AKA anticholinesterase drugs or antimyasthenics
- -Administering with food helps alleviate GI s/e
- *Instruct the patient to eat meals 45 minutes to 1 hour after taking these drugs to avoid aspiration; this is very important if the patient has bulbar involvement
- -Potential adverse effect is a cholinergic crisis: sudden increases in weakness and the inability to clear secretions, swallow, or breathe adequately indicate that the patient is experiencing the crisis
- -May be accomplished with the use of corticosteroids or chemotherapeutic agents
- -Prednisone is given initially to produce remission and to controland improve symptoms
- -Tapered over a period of weeks to months
- -IVIG may also be used for acute disease management or as a long term option for disease refractory to other tx
- -Exacerbation caused by not enough anticholinesterase meds
- -May be caused by an infection
- -Priority of care is maintaining adequate respiratory function
- -Increased pulse and respirations
- -Rise in blood pressure
- -Bowel and bladder incontinence
- -Decreased urine output
- -Absence of cough and swallow reflex
-When an increase in muscle weakness leads to an overdose of anticholinesterase meds
- -Dysphagia (difficulty swallowing)
- -Dysarthria (painful joints)
- -Increased lacrimation (tearing)
- -Increased salivation
- -Generalized weakness
- -Acute exacerbation of muscle weakness caused by too many anticholinesterase meds
- -Do not give anticholinergic drugs while patient is maintained with mechanical ventilator
- -Abdominal cramps
- -Blurred vision
- -Pallor-Facial muscle twitching
- -Pupillary miosis
Tensilon test important diagnostic becuase may have a temporary improvement in myasthenic crisis but will show no or worsening of symptoms in cholinergic crisis
Atropine 1 mg IV may be given and repeated if necessary- need to observe patient carefully because secretions can be thickened; more difficult with airway clearance and possible mucous plug (for cholinergic crisis)
- **Rest is critical because increased fatigue can precipitate a crisis
Difficulty maintaining adequate intake of food and fluid- muscles for chewing and swallowing become weakened and tire easily- small frequent meals, increased calorie snacks often well tolerated
To check for effectiveness of calorie count: I&O, prealbumin, daily weights
Surgical Management: Thymectomy
- Removal of the thymus gland
- -Usually performed early in the disease
- -Not always immediately effective, may take several years if at all
- -Those who have surgery within 2 years of onset of symptoms show most improvement
- Pre-op Care:
- -Important to be optimistic but do not make promises since remission or improvement are not predictable
- -Immediatley before surgery Mestinon may be given with a small amount of water to keep the patient stable during and after surgery
- -If steroids have been used they need to be given before surgery and tapered off after
- -Antibiotics administered immediatley before or during surgery
- -Plasmapheresis may be used before and after surgery to decrease circulating antibodies more quickly
- 2 different approaches to surgery: transcervical incision
- -Minimal access technique
- -More popular
- -Allows more rapid recovery with less discomfort especially if used with VATS technique (video assisted thorascope)
- -BUT is only for patients who do not have a thymoma
- -Small dressing change and IV
- Sternal Split:
- -Older procedure that is preferred when a patient has a thymoma
- -Allows the surgeon to see directly into the mediastinum and areas around the thymus
- -Patient is usually admitted to ICU after surgery
- -Presence of myasthenic weakness canstill complicate the management
- -Most patient require gradual weaning from ventilator
- -Suctioning is performed as necessary and need to pay attention for the respiratory hygiene
- -Observe carefully for signs of pneumothorax or hemothorax (chest pain, sudden SOB, diminished or absent breath sounds, restlessness or change is VS) and report these signs immediatley
- -Provide O2 and raise the HOB to atleast 45 degrees
- -Provide chest tube care and assess for s/s of an infection
Community Based Care:
- Home Care:
- -Little preparation of the home setting
- -May need assistive devices
- -Team must make sure all needs can be met
May need collaboration with PT/OT to check on any necessary modifications to the home
The more the patient and family know about the disease and meds used for treatment the less likely that complications will happen. Discuss factors that increase the rist of exacerbation, teach the importance of collaborating with the health care team to monitor muscle strenght, ability to perform ADL's and the need to adjust meds. Stress the importance of lifestyle adaptations and knowing and reporting the signs of exacerbation (need to plan activities that allow rest periods to conserve energy)
Provide drug regimen in written format and the importance of maintaining therapeutic blood levels by taking meds on time and as prescribed and not missing or postponing doses- side effects of anticholinesterase drugs- NEED to encourage family members to learn resuscitation
- Health Teaching:
- -Encourage patient and family to ask questions
- -Stress importance of lifestyle adaptations such as avoiding heat, crowds, overeating, erratic changes in sleep habits, or emotional extremes
- -Teach signs of exacerbation
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