CALLING DR. McDREAMY! Just days before PATRICK DEMPSEY got attacked and choked by costar ISAIAH “Dr. McJealous” WASHINGTON on the “Grey’s Anatomy” set, Dempsey spotted a crewmember hanging onto a pole, looking white as a doc’s smock! “What’s wrong?” he asked – and when the guy admitted he was dizzy and couldn’t feel his legs, the star yelled to a staffer: “Call an ambulance… NOW!” The stricken guy protested, but Dempsey and a crewmember carried him to a lounge chair. Paramedics arrived swiftly, took vital signs… and hustled him to Emergency. Turns out he was seriously ill, suffering from a blood clot in his leg that could have traveled and killed him if he hadn’t gotten fast treatment. (Good work, McDreamy! And McJealous, remember your physicians’ oath: “First… do no harm, dammit!”)