They're swarming Derek like locusts, and Dean has a moment to think, of course, there's power in an alpha's blood before his thoughts turn to wondering how much Derek can take. He's strong, no question, but not even a werewolf can heal from exsanguination.

The guy needs help, because he came when he thought Dean needed help, and that goes a long way in Dean's book. Retrieving his sword, Dean begins the long process of cutting his way to him, anger giving him the focus he needs to slice through vampire after vampire.