Final answer:
The nurse's priority is to assist with plasmapheresis.
Step-by-step explanation:
The nurse's priority in this situation is to assist with plasmapheresis. Plasmapheresis is a procedure in which the plasma is separated from the blood and removed, along with the antibodies that are causing the autoimmune reaction in myasthenia gravis. By removing the antibodies from the client's blood, plasmapheresis can help alleviate the symptoms and prevent further muscle weakness.