Correct Answer: C

Rationale: Furosemide is a potassium-wasting diuretic. A low potassium level may cause weakness and palpitations. Telling the patient to rest more often won't help the patient if she's hypokalemic. Digoxin isn't causing the patient's symptoms, so she doesn't need to stop taking it. The patient should probably avoid caffeine, but this wouldn't resolve potassium depletion.

Correct Answer: B

Rationale: In elderly patients, the clinical manifestations of fluid and electrolyte disturbances may be subtle or atypical. For example, fluid deficit may cause confusion or cognitive impairment in the elderly person.

Correct Answer: A

Rationale: Signs and symptoms of hypomagnesemia are largely confined to the neuromuscular system and include confusion, tremor, tetany, laryngeal stridor, and ataxia.

Correct Answer: D

Rationale: Third-spacing fluid shift, which occurs when fluid moves out of the intravascular space but not into the intracellular space, can cause hypovolemia.

Correct Answer: D

Rationale: The symptoms of hypokalemia include GI, cardiac, renal, respiratory, and neurologic disturbances. The use of potassium-wasting diuretics, such as hydrochlorothiazide, without potassium replacement therapy is a primary cause of hypokalemia.