For Autonomy: patient must first have informed consent (be aware of alternative treatment...made an informed decision) and as physicians we must honour the patient's right to request/refuse medical care. It is basically acknowledging that the patient is the decision maker.
Beneficence: A physician must always act in the patient's best interest (this might interfere with autonomy) but in the end the patient always has the right to decide.
A 27 year old woman is involuntarily committed to the psych ward. Her physicians note persistently elevated BP with MAP of 120 mm Hg over the week. Px has been asymptomatic. Her physicians would like to begin standard treatment but the px refuses. She understands the risks, benefits and outcomes that would result with or without treatment. What has priority in the care of this patient?
B- Duty to other patients
C- Informed consent
E- Patient autonomy
Autonomy is the patient's right to accept or refuse any treatment - even life saving one - given that he/she was competent and well informed about risks and benefits. Autonomy takes precedence over anything else when it comes to USMLE questions (ALWAYS!) and real life practice (most of the time).
Beneficence is simply applying the best interest standard. its used when the patient is incompetent and the surrogate making the decision fails to use the subjective standard or substituted judgement criteria.