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Myasthenia Gravis
- -a neuromuscular disease characterized by weakness and abnormal fatigue of the voluntary muscles.
- -(+)defect in the transmission of nerve impulses at the myoneural junction occurs.
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Causes of MG:
- -insufficient secretion of acetylcholine.
- -excessive secretion of cholinesterase.
- -unresponsiveness of the muscle fibers to the acetylcholine.
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Assessment of MG:
- ~weakness and fatigue
- ~diff chewing and swallowing
- ~ptosis, diplopia
- ~weak, hoarse voice
- ~DOB
- ~diminished breath sound
- ~resp paralysis and failure
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Intervention for MG:
- >MONITOR: RR and status, ability to cough; resp failure
- -deep breath accurately
- -maintain SUCTIONING and EMERGENCY equipment @ bedside
- >MONITOR: speech and ability to swallow (px aspiration)
- -SIT UP when eating
- >assess muscle status
- -conserve strength (plan short activities)
- >WOF: myathenia crisis and cholinergic crisis
- >AVOID: stress, infection and OTC meds
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Antimyasthenic meds: anticholinesterase meds
- -relieve muscle weakness by BLOCKING Act breakdown at the neuromuscular junction.
- -used to tx or dx MG or to distinguish CC frm MC.
- -MEDS: ambenonium chloride (mytelase), endrophonium chloride (tensilon), neostigmine bromide (prostigmin), pyridostigmine (mestinon)
- INT:
- ~assess neuromuscular status (reflex, muscle strength and gait)
- ~WOF s/sx of med overdose (CC) or underdose (MC)
- ~take meds on time to maintain therapeutic blood level, thus px weakness
- ~take meds with SMALL amount of food (px GIT sx)
- ~eat 45-60 mins after taking meds to decrease risk of aspiration
- ~lifelong therapy
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Myasthenia crisis:
- -an acute exacerbation of the disease
- >CAUSE: rapid, unrecognized progression of the disease, inadequate amt of meds, fatigue or stress
- S/SX:
- ↥ PR, RR and BP
- Dyspnea, anoxia and cyanosis
- ↧ UO
- (-)cough and swallow reflex
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INT for Myasthenic crisis:
- WOF s/sx.
- ↥ anticholinesterase meds
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Cholinergic crisis:
- -results in depolarization of the motor end plates.
- >CAUSE: overmedication with anticholinesterase.
- S/SX:
- (+)abdominal cramps
- N&V,diarrhea
- blurred vision
- pallor
- facial muscle twitching
- hypotension
- pupillary miosis
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INT for Cholinergic crises:
- !WITHHOLD anticholinesterase meds
- ANTIDOTE: atropine sulate
*have atropine sulfate available when performing TENSILON TEST.
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Endrophonium test: tensilon test
- -used to dx MG and used to differentiate MC and CC.
- -@ risk for: ventricular fibrillation and cardiac arrest.
- TO DX MG:
- -(+) pt shows improvement in muscle strength after administration (muscle tone: 30-60 sec; muscle improvement lasts: 4-5mins)
- -(-) pt shows NO improvement in muscle strength, and strength may deteriorate after injection.
- TO DIFF CRISIS:
- >MG: strength IMPROVES, pt needs more meds.
- >CC: weakness is more severe, the pt is overmedicated; give atropine sulfate (antidote)
- -given IV
- -can CAUSE: bronchospasm, laryngospasm, hypotension, bradycardia and cardiac arrest
- -ATROPINE SULFATE-antidote for overdose
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N/I for MG:
- -conserve energy
- -rest before meals
- -sit upright during meals
- -soft foods with gravy or sauce; (+) choking-pureed foods with a pudding like consistency.
- -suction available @ home
- -tape eyes for short intervals and instill artificial tears
- -AVOID factors that exacerbate sx: emotional stress, infections (resp), vigorous physical activity, some meds, and high environmental temp.
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