[SIZE=2]Head to room S3.You'll find a key there.Head to the roof via the stairway and use the Roof Key to unlock it.
When you come back in from here you'll have a scene with Pyramid Head and find yourself in the Special Treatment Room.Head through the door to the left of the sign.You'll find a code splattered in blood on the wall.You may want to write it down with the other code you should have found earlier.
Go to the second floor to check on Maria and then go to room S14-it's the last door in the hall.There is a box there which needs 2 codes and 2 keys to be opened.
There's a little ways to go before getting out of the hospital from here-this should get you going in the right direction.[/SIZE]