(CBS) — Lurie Children’s Hospital in downtown Chicago has seen at least 21 patients for underage drinking in the ER since Friday, reports WBBM’s Mariam Sobh.

According to officials at the hospital, they see twice the amount of underage drinking cases during Lollapalooza than any other festival.

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Dr. Walter Eppich, an ER physician at Lurie Children’s Hospital, says it is part of a trend that underage teens take part in before going to venues where they can’t get alcohol.

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“They’ve been calling it themselves ‘pre-gaming’ so they drink vodka or other hard liquors before they go to Lollapalooza and then attempt to get a buzz,” he says.

Eppich says they’ve seen kids as young as 14 in the ER and these teens often come so impaired the only thing they can remember is their name until the effects of the alcohol wear off.

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Lurie treated 21 underage drinkers on Friday and Saturday.