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: C

Rationale: Probably the most common cause of metabolic alkalosis is vomiting or gastric suction with loss of hydrogen and chloride ions. The disorder also occurs in pyloric stenosis in which only gastric fluid is lost. Vomiting, gastric suction, and pyloric stenosis all remove potassium and can cause hypokalemia.

Correct Answer: B

Rationale: The correct answer is B. In elderly patients, fluid deficits can lead to confusion and cognitive impairment. Limiting fluids can disrupt the body's balance, leading to such symptoms. Adjusting the timing of fluids can help maintain hydration without causing nighttime interruptions. Choices A, C, and D are incorrect because they do not address the underlying issue of fluid imbalance causing confusion. Choice A suggests unnecessary hospital readmission and medication adjustments. Choice C incorrectly normalizes confusion post-surgery and suggests it is safe not to urinate at night, which can exacerbate the issue. Choice D inaccurately attributes confusion to sleep loss rather than fluid imbalance.

Correct Answer: B

Rationale: Tetany is the most characteristic manifestation of hypocalcemia and hypomagnesemia. Sensations of tingling may occur in the tips of the fingers, around the mouth, and less commonly in the feet. Taking a normal blood pressure could illicit a carpal spasm if it creates slight ischemia of the ulnar nerve.

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.