(1) A principal may confer a power of attorney for health care thereby designating another competent adult as attorney in fact for health care decisions in accordance with sections 30-3401 to 30-3432. A principal may also designate another competent adult as a successor attorney in fact to serve in place of the original attorney in fact when the original attorney in fact is not reasonably available or is unable or unwilling to serve as an attorney in fact. If, after the authority of a successor attorney in fact has commenced, the original attorney in fact becomes available, able, and willing to serve as attorney in fact, the authority of the successor attorney in fact shall cease and the authority of the original designee shall commence.

(2) There shall be a rebuttable presumption that every adult is competent for purposes of executing a power of attorney for health care unless such adult has been adjudged incompetent or unless a guardian has been appointed for such adult.