A 45-year-old attorney travels to the Caribbean islands for vacation. While away she develops profuse vomiting and diarrhea due to an unknown gastrointestinal (GI) pathogen. She is able to fly home but becomes profoundly dehydrated, unable to keep up with her GI fluid losses. On her second day back from the trip, her husband returns home from work to find her somnolent and minimally responsive with decreased respiratory effort. He immediately calls 911 and an ambulance arrives to transport her to her local emergency department (ED).

In the ED she is clearly dehydrated with dry mucous membranes and loss of her normal skin turgor. Her heart rate is 124 and her blood pressure is measured at 100/70 mm Hg. In addition, she appears somnolent and has a severely diminished respiratory drive, requiring endotracheal intubation for her severe hypoventilation. Her initial arterial blood gas shows a pH of 7.55 (normal 7.40 to 7.44), with a partial pressure of carbon dioxide (PCO₂) of 66 mm Hg (normal 40). Her arterial partial pressure of oxygen is normal at 95 mm Hg.

With concern for dehydration, the covering ED physician places a central venous catheter and begins intravenously administering fluids to replace volume loss. After a half hour of volume administration, the patient returns to stable vital signs and again begins to produce urine. However, the nurse is concerned because despite this improvement, the patient remains weak and lethargic, unable to follow commands. In addition, the cardiac monitor shows what the nurse believes to be an abnormal rhythm. The resident orders an electrocardiogram (ECG), which shows prominent U waves. A serumelectrolyte panel is ordered, which reveals a potassium level of 1.7 mg/dL (nl 3.5 to 5.0 mg/dL). After aggressive potassium repletion, the patient once again begins following commands and regains her strength, able to tolerate eventual extubation. She is discharged home on hospital day number two.