I couldn´t see the episode 4x16 on the head of a pin, but I saw that Dean was in hospital. Can somebody tell me why?

If you really want to know, then I should warn you that SPOILERS are coming. The angels had captured Alistair, and he was tied up in a Devil's Trap, but some water dripped and Devil's Trap broke, so Alistair beat the crap out of Dean, that's why he was in the hospital.

while dean was torturing alistair, the devil's trap he was in broke, and he beat dean up reeeeal bad

im not sure but i think becase the hell hound riped him up

Alistair was being tortured by Dean while he was in a Devil Trap. Some sort of water source leaked and broke the trap setting Alistair free. After he was free he began to beat Dean senseless. After a few minutes Sam busts in and kills Alistair, or more like sent him back to Hell.

dean was bet by airistal forgive the spelling

The demons sent a deisel big rig and broad sided the impala after the boys and their dad had fought the yellow eyed demon. Dean was fatally wounded. John made the deal with the yellow eyed demon to take his soul and save dean. which he did.

Alastair beat the crap out of him.

alastair beat him cause the devil trap is broke