I am #2 on a POA for Health for my mother. The POA has been enacted. My brother is #1, and must be consulted first. How do I change the POA?

I’m a little confused by the “POA has been enacted” are you talking about a DPOA a MPOA or a simply POA? I ask because as a POA you have access to all the info and can talk to Dr’s. In my experience the chain of command if you will is written in for major decision, take someone off life support, sell the house or when everyone doesn’t agree and a decision has to be made that sort of thing. As far as getting information etc at the hospital, talking over treatment and meds if you are a medical proxy or MPOA even shared with others there aren’t many things you should run into problems doing. Now if you and your brother are at constant odds you might need to tread a bit more carefully but I’m not even sure the hospital will weigh in an addendum about who can do what when they see your name as MPOA even when your brother also has it. You might want to check the legal documents thoroughly and make sure you have a full understanding of your rights. Do you have copies of the legal documents, does the hospital or did you tell them your brother needs to make all the decisions because that’s your understanding?

Only your mother can change that. She chose your brother to be first for some reason.

You do not change the POA. Your mother made your brother primary and you must accept that. It does not matter that you are closer or that he lives farther.

If your mother has dementia and is no longer competent to change the appointment I don't think it can be changed very easily at all.
Is this POA for health care? What an absolute shame that you are the one taking her to treatment and appointments and have no way to get information. As POA I wonder if your brother is able by phone to appoint you as Health Care POA thru a first phone call, since you are listed as the second already. I don't even know if this is possible.
Do you and your brother agree on the fundamentals of her care going forward? Does he also wish for you to have the POA for Health care? Because if he does he could resign as health care POA and you would be next in line.

Is your Mom too demented to go to an attorney to change this? Have you spoken with your bro about how to do this? Your Mom doesn't have to have a great memory to appoint you health care POA, she just needs to have the wherewithall to prove to the notary that she understands what she is doing and why she is doing it (she is in your direct care) in appointing you.