Correct Answer: C

Rationale: Fluid loss from the extracellular compartment can be caused by abdominal surgery.

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: A

Rationale: To gauge a patient's magnesium status, the nurse should check deep tendon reflexes. If the reflex is absent, this may indicate high serum magnesium.

Correct Answer: B

Rationale: Infants are particularly vulnerable to dehydration due to diarrhea, as they have a higher fluid turnover and less reserve.

Correct Answer: D

Rationale: Renin is released by the juxtaglomerular cells of the kidneys in response to decreased renal perfusion. Angiotensin-converting enzyme converts angiotensin I to angiotensin II. Angiotensin II, with its vasoconstrictor properties, increases arterial perfusion pressure and stimulates thirst. As the sympathetic nervous system is stimulated, aldosterone is released in response to an increased release of renin, which decreases urine production. Based on the nursing assessment and mechanism of injury, this is the most likely cause of the lower urine output.