The fluorescent lights of the emergency department flicker as you rub your tired eyes. It’s 2 a.m. on a Saturday, and every bay seems to be groaning under the weight of the night. A drunk twisted ankle is arguing with a nurse, a toddler with croup is barking somewhere behind a curtain, and the overhead monitors keep up their relentless electronic chorus. You’ve just finished stabilizing a trauma patient and are reaching for a lukewarm coffee when the charge nurse catches your eye and waves you over, her expression all business.