A patient exhibits ptosis of both eyes and the provider orders edrophonium (Tensilon). The nurse notes immediate improvement of the ptosis.
The nurse understands that this patient most likely has which disorder?

Choice A rationale

Magnesium plays a role in muscle relaxation but is not primarily responsible for muscle contraction. It helps in stabilizing the muscle membrane by acting as a natural calcium blocker. Deficiency in magnesium can lead to muscle cramps and spasms, but it does not directly cause muscle contraction and relaxation processes.

Choice B rationale

Chloride is an essential electrolyte involved in maintaining fluid balance and acid-base balance, but it does not directly influence muscle contraction and relaxation. It works in conjunction with sodium to regulate osmotic pressure and acid-base balance.

Choice C rationale

Calcium is crucial for muscle contraction. It is released from the sarcoplasmic reticulum within the muscle cells and binds to troponin, causing a conformational change that allows actin and myosin to interact and generate contraction. During relaxation, calcium ions are pumped back into the sarcoplasmic reticulum.

Choice D rationale

Hydrogen ions are involved in pH balance and acid-base regulation but do not directly affect muscle contraction and relaxation. Excess hydrogen ions (acidosis) can impair muscle function, but they are not the primary factor in muscle contraction processes.

Choice A rationale

Reassuring the client without addressing the persistent cough would not be appropriate as it may signal a need for a different medication. The ACE inhibitor captopril can cause a bothersome, persistent cough in some patients due to increased bradykinin levels.

Choice B rationale

Instructing the patient to stop the medication immediately is not advised without consulting the healthcare provider. While the cough is a known side effect, stopping the medication abruptly may lead to unmanaged hypertension.

Choice C rationale

Scheduling an appointment with the provider to discuss changing to an angiotensin II receptor blocker (ARB) is appropriate. ARBs do not typically cause a persistent cough, making them a suitable alternative for patients who experience this side effect with ACE inhibitors.

Choice D rationale

Instructing the patient to go to the emergency room immediately is unnecessary as the persistent cough is a common side effect of ACE inhibitors and not an emergency situation. Emergency action is warranted for symptoms of angioedema, such as swelling of the face or throat.