If you get knocked out, you have the ability to revive your teammate by standing next to them for a few seconds to give them the opportunity to recover. (theswitcheffect.net)
While playing as the medic is sadly just a little boring unless you're diving in under the monster's feet while wearing your invisibility cloak to revive another teammate who got a little brave. (nosleepgamer.com)
Thankfully, this version of Evolve's medic class (there will be at least two in the final game) also has a temporary cloaking device to turn invisible, giving you an extra chance of reviving a teammate without being detected. (nosleepgamer.com)