Make sure you get good sleep between shifts. If you get off at midnight, can you get home and to bed at a reasonable hour? At least get some sleep before your 7:00 am interview? Make sure you take a shower before you go - usually most folks look fresh after a shower no matter how tired they are, they just wilt later. Why not have a cup-of-jo enroute? And it is a hospital interview, so they should understand crazy shift work. Not quite like trying to get into something completely different, where getting off at midnight would strike them as odd.