“I’m in,” repeat the doctors and residents at regular intervals on “The Pitt,” the Emmy-nominated HBO series set during a tumultuous day in a Pittsburgh trauma medical center. I’ve never been one for medical shows, for one thing, and “The Pitt” often feels like it’s aiming to be the medical show to end all medical shows, with blood and guts to rival a slasher film and enough technical jargon to fill reams of paperwork. That kind of conviction can’t be faked, and on the level of emotional realism, “The Pitt” is a triumph. When an elderly postal worker named Willie, wheeled in with a broken pacemaker, shows surprising knowledge of the medical procedures being used on him, the doctors question him. A grumpy hospital flack shows up at inopportune times to berate Dr. Robby about the bottom line and “patient satisfaction scores,” which in turn gives him the opportunity for mini-rants about being understaffed.