Mrs. Ursula de Silva is a 47-year-old female with a history of epilepsy, controlled on carbamazepine. Ursula and her husband, George, both present to the emergency department after a recent safari vacation with diarrhea and weakness. On history, Ursula tells you that she has had 5 days of watery diarrhea that started near the end of her trip. Physical examination shows a HR of 110 beats/min, BP 105/80 mm Hg, RR 30 breaths/min, oxygen saturation 99% on room air. Examination also reveals dry mucous membranes and axilla, and a low JVP.