Generally, a competent adult of legal age or meeting the legal requirements for emancipation can refuse treatment at any time regardless of their physical condition. They could be missing an arm, a leg, and one eye, and bleeding to death and if they dont want to receive care or be transported then you really have no grounds to force care. You just have to be really persuasive or wait til their mental status becomes altered from hypoxia and provide care under the law of implied consent. And if you really wanted to debate the issue, does implied consent still apply if a pt. makes their wishes known before they become altered or unconscious from their injuries? Or does it only apply if you find a pt. in an altered or unconscious state?
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Any pt. that is contemplating harm to themselves or others regardless of compency is automatically getting a ride to the hospital cause obviously if they were in a "normal" state of mind they would not want to harm themselves or someone else. The pt. has no choice here.
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Minors only get transported if I cant get ahold of a parent, relative, or legal guardian to come to the scene or give verbal consent for refusal over the phone.
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An area I find scary is when providers release a MVC pt. that is intoxicated to law enforcement. Legally, these pt's. cannot be released to a person of a lesser level of training then you and the pt. obviously cannot decide for themselves to refuse given the intoxicated state. What happens when PD is transporting to the barracks or wherever and the pt. crashs? Who is liable here? I've had this situation and consulted medical command for their ok before releasing to law enforcement.
This is an area of many fine lines and circumstances but Ive always been told and operate under the primise that as long as you do what is in the best interest of the pt, you are gonna be protecting yourself.