Do you think EMT's would give blood in the field? No, so bloodtype isn't likely to be used.
The name they will probably use.
I want to be a paramedic and if I see a patient with a dog-tag, I would probably use it's name and address.
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''It's time for Plan B...'' ''We have a Plan B?'' ''No, but it's time for one.'' -Stargate SG-1