SAN FRANCISCO (AP) -- The young man stumbled into the emergency room late one night after a house party, saying his heart wouldn't stop pounding and he could barely breathe after downing liquor mixed with energy drinks.
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.
From 2007 to 2011, the government estimates the number of emergency room visits involving the neon-labeled beverages shot up from about 10,000 to more than 20,000. Most of the cases involved teens or young adults, according to the survey of the nation's hospitals released late last week by the Substance Abuse and Mental Health Services Administration.
More than half of the patients considered in the survey told doctors they had consumed only energy drinks. In 2011, about 42 percent of the cases involved energy drinks in combination with alcohol or drugs, such as the stimulants Adderall or Ritalin.
The beverage industry says energy drinks are safe and there is no proof linking the products to adverse reactions.
The report doesn't specify which symptoms brought people to the emergency room, but it calls energy drink consumption a "rising public health problem" that can cause insomnia, nervousness, headache, fast heartbeat and seizures that are severe enough to require emergency care.
Several emergency physicians said they had seen a clear uptick in the number of patients suffering from irregular heartbeats, anxiety and heart attacks who said they had recently downed an energy drink.
"A lot of people don't realize the strength of these things. I had someone come in recently who had drunk three energy drinks in an hour, which is the equivalent of 15 cups of coffee," said Howard Mell, an emergency physician in the suburbs of Cleveland, who serves as a spokesman for the American College of Emergency Physicians. "Essentially he gave himself a stress test and thankfully he passed. But if he had a weak heart or suffered from coronary disease and didn't know it, this could have precipitated very bad things."
The findings came as concerns over energy drinks have intensified following reports last fall of 18 deaths possibly tied to the drinks and so-called energy shots -- including a 14-year-old Maryland girl whose family filed a lawsuit after she drank two large cans of Monster Energy drinks and died. Monster says its products were not responsible for the death.
Two senators are calling for the Food and Drug Administration to investigate safety concerns about energy drinks and their ingredients.
Late last year, the FDA asked the U.S. Health and Human Services to update the figures its substance abuse research arm compiles about emergency room visits tied to energy drinks.
The Substance Abuse and Mental Health Services Administration's survey was based on responses it receives from about 230 hospitals each year, a representative sample of about 5 percent of emergency departments nationwide. The agency then uses those responses to estimate the number of energy drink-related emergency department visits nationwide.
The more than 20,000 cases estimated for 2011 represent a small portion of the annual 136 million emergency room visits tracked by Centers for Disease Control and Prevention.
The FDA said it was considering the findings and pressing for more details as it undertakes a broad review of the safety of energy drinks and related ingredients this spring.
"We will examine this additional information ... as a part of our ongoing investigation into potential safety issues surrounding the use of energy-drink products," FDA spokeswoman Shelly Burgess said in a statement.
Beverage manufacturers fired back at the survey, saying the statistics were misleading and taken out of context.
"This report does not share information about the overall health of those who may have consumed energy drinks, or what symptoms brought them to the ER in the first place," the American Beverage Association said in a statement. "There is no basis by which to understand the overall caffeine intake of any of these individuals -- from all sources."