Damage in the Hero@Heart system is more cinematic, and thus healing it is a bit looser than it might be in other such games. If a person's arm has been ripped off by a chainsaw, the damage would probably be too severe to come back from, but in game terms, the GM could use the rules found here to save the arm with just a field medic's kit. The rules attempt to be realistic, but not so realistic that an injured character becomes worthless.
Cumulative damage of one type can be healed all together, but injuries of different types (Sharp, Blunt, etc.) must be healed separately. The GM decides based on the type sand severity of the injury if he feels First Aid will do or if the injury will need Surgery to heal. The roll is then made, and the success rate indicates how much of the injury will be healed. First Aid takes ten minutes per rank, and Surgery takes an hour per rank to perform. Once the roll has been made, another roll cannot be made by that healer or any other for 24 hours on the same injury. The healer could, however, move on to other injuries. Note that no Fatigue is healed during this time, but Surgery actually causes Fatigue damage to the patient, one point per rank of success.
Healing Fatigue Damage
Fatigue damage can only be healed by rest. For every hour that a person rests undisturbed, they gain back one Fatigue damage. This damage cannot be healed, however, if the person has untreated injuries.