Emergency physician Steve Sun soon found the patient was so dehydrated he was going into kidney failure — one of many troubling cases Sun says he has treated in recent years tied to energy drink consumption.

Sun's changing caseload appears in line with a new government survey that suggests the number of people seeking emergency treatment after consuming energy drinks has doubled nationwide during the past four years, the same period in which the supercharged drink industry has surged in popularity in convenience stores, bars and on college campuses.

"Five years ago, perhaps I would see one or two cases every three months or so. Now we're consistently seeing about two cases per month," said Sun, assistant medical director of the emergency department at St. Mary's Medical Center, on the edge of San Francisco's Golden Gate Park.