I don't care that much about KDR, only about credit to team. That's why I have a 2:1 win/lose ratio despite my average KDR.
When I play Medic I usually don't kill that much, I focus on dropping my dual heal specced medpacks and reviving people.

EDIT FOR ACTUAL ADVICE: Don't rush out blindly, access the situation first, look around. Run from cover to cover, never stay out in the open for long unless you're really sure that you're being backed up or the coast is clear.
Camping helps too

This post has been edited by Zephro: May 31 2010, 10:51 PM