General Discussion

For some things, yes. But there are also some decisions which the spouse cannot make unless granted express permission in advance.

The forms also typically raise questions which you might not think of (e.g. if you are unlikely to recover, do you want your spouse to terminate hydration? nutrition? pain relief, machines breathing for you?). It is good to go through the forms together so your spouse is clear what you want.

I agree that you don't generally need an attorney - the forms are pretty standard, and state-specific forms are almost certainly available from the hospital or state bar association.

But you are far better off with express authorization AND an advance discussion than hoping that the hospital follows your wishes, the law grants you all the permission you need, or that your spouse knows all of the details about where your line in the sand is.