violence_hblood 0 and violence_hgibs 0 should do the trick. You'll probably still have the little blood spots on the players, though. For that, I think you need r_maxmodeldecal 0 or something, but that might crash your game, I'm not sure.
They're console commands. You can type them into the console in-game or you can put them in your config.cfg or autoexec.cfg. Also, it should be r_maxmodeldecal 1, not 0.