Of course, an "explosion" is a very vague spoiler. Assuming it's a literal explosion — and not, say, a metaphorical emotional one — that could mean anything from a science experiment gone wrong up to the whole dang hospital blowing up (not that we think it will be that bad ... right?).
And this spoiler also doesn't clarify if our docs will be in danger, or if this will be more like the gas tanker explosion in Season 9, Episode 19: "Can't Fight This Feeling," where the docs were tasked with saving lives, but weren't at much risk themselves.