Normally is the word used in the italian language to define the "stretcher" (i.e: he was carried away on a stretcher)
It has then become widely used with two particular meanings:
1. As a noun, "La Barella" is the italian slang for Cocaine (probably more in the north-west regions as Lombardy or Piedmont)
2. As a verb, means "freaking out", "getting wasted", being totally fucked up
1. Oh, zio, porta la barella ! - yo, bro, bring the cocaine
2. Zio, stai sbarellando di brutto !! - dude, you're freaking out of your goddamn mind!
3. Minchia Tony l'altro giorno ha sbarellato! - Fuck, Tony got really mad the other day
4. Ou, ripigliati che stai sbarellando - dude, you're losin it, get your shit 2gether