To get a clean hospital, save the game and reload it again when the hospital becomes full. All of the garbage and patients will dissapear, allowing a fresh start!

Level  Password
2      X, O, Square, Triangle, Triangle, O, Square, X
3      O, O, Triangle, Square, X, Triangle, O, Triangle
4      Square, Triangle, O, Square, X, X, Triangle, O
5      O, Triangle, Square, O, X, Triangle, O, Square 
6      Square, Triangle, Square, O, X, Square, X, O
7      Square, Triangle, Triangle, O, X, Square, Triangle, O
8      X, Triangle, Square, O, Triangle, O, Square, X
9      Triangle, Square, X, Triangle, O, X, Triangle, Square
10     O, Square, X, Triangle, Square, X, O, Square
11     Triangle, O, Square, O, Triangle, Square, O, X
12     O, Square, X, X, Square, O, Square, Triangle

If there are rats in your hospital, just put a plant in front of the hole.

Hit pause at the beginning of a level and go to the stop watch symbol. Now press and hold L1 until the indicator reaches the left of the bar. You now have extra time to build your rooms.