As seen in the Dayz development blogs, players can preform blood transfusions. Blood types are a factor in this medical system. In Arma 3 for example you could have a teammate bleeding out and the medic needs to preform a transfusion. Problem is the player or AI with the needed blood type is engaging the enemy, so you have to have another player or AI take over as he/her goes to stand beside the patient bleeding out so the medic can preform the transfusion.
Thinking on a more realistic note, having a combat medic put a saline solution or another solution into the individual's body so that they can be made stable. The animations for such would assist for medical scripts.