A 23-year-old ballet dancer arrived at the Emergency Department after collapsing during a week of strenuous rehearsals for an upcoming production. The patient reported that she had been in good health and takes no medication except the occasional loratadine (Claritin) for her seasonal allergies. Further questioning revealed that the patient "lives on" diet colas to keep her weight down for dancing; she said she does not like the "taste" of water. Assessment in the Emergency Department revealed the patient to have a pulse of 140, blood pressure of 78/62 and poor skin turgor. She required aggressive intravenous fluid resuscitation.