A nurse in the emergency department is caring for a client who has been experiencing profuse vomiting and watery diarrhea for the past 24 hours. The client reports muscle weakness and palpitations. Based on these findings, the client is at greatest risk for developing which of the following conditions?

Choice A rationale: Hypercalcemia typically stems from hyperparathyroidism or bone malignancy; it is not a primary complication of acute gastrointestinal fluid loss from vomiting or diarrhea. Choice B rationale: Hypertension is unlikely in this scenario; significant fluid loss through vomiting and diarrhea more commonly leads to hypovolemia, resulting in decreased blood pressure or hypotension. Choice C rationale: Hypokalemia occurs because gastric contents and intestinal fluids are rich in potassium; excessive loss through vomiting and diarrhea directly depletes serum potassium levels, causing cardiac and muscular symptoms. Choice D rationale: Hypernatremia can occur with dehydration, but in secretory diarrhea, sodium and water are often lost together, making the clinical focus on potassium replacement more urgent for cardiac stability. Choice E rationale: Hypoglycemia is not the primary risk here; while oral intake may be low, the body's stress response to illness typically maintains or elevates blood glucose through gluconeogenesis.