Just saw this on Sportscenter, very freaky stuff. Very reminiscent of the Malarchuk injury from the 80's, seems like Zednik was very fast to react though and skated directly to his trainer. Hope he recovers quickly. The amount of blood on the ice was just sickening.
Here is the video of Malarchuk getting his jugular cut... very crazy.
YouTube - Clint Malarchuk gets throat slit by skate
Every other country in the world requires neck guards for until you are 18 for hockey. I'm not sure if USA has followed this rule yet, I know they didn't when I was playing.