Who makes medical decisions if patient unconscious?

It can vary some by state.

In general it goes in this order (for adults):

1) The patient, himself or herself - if they have a document that specifies his or her wishes (a living will).

2) The healthcare power of attourney - This would be a person that the patient has specified to make decisions. If there is a valid written POA in effect this person takes precedence over other family members in most states.

3) The spouse.

4) The children.

5) The parents.

6) Other relatives.

7) A friend or close acquaintance who claims to either have spoken with them about their wishes or knows the patient well enough to know what he or she would want.

8) A court appointed guardian.

It is always best if there is a document in writing but in general the treating team is to best determine the patient's wishes and follow them, even of they have to rely on verbal reports. For instance, if someone comes forward and states that the patient told them they did or did not want a treatment and that person is felt to be credible then that statement should take precedence over the wishes of other family members. Of course, the family may decide to fight it in court and the treating team often will defer to the family improperly out of fears of law suits or ignorance.

A patient who is conscious and is able to make his or wishes known can countermand / reverse any written document at any time they are able. So if you have a living will that says not to do something and when the situation arises you change your mind all you need to do is to say so and your most recent directive should be followed.

If there is no one available to make a decision then it is generally assumed that the patient wants life saving care and it is given. This is not to say that all care must be given until someone says not to give it. If the treating team feels that a treatment is highly unlikely to benefit a patient (if it is deemed "futile") then they are under no obligation to offer it even if the patient or family demand it.