It used to be that a person of or over 18 years of age could, by instrument in writing, appoint a person over 18 years of age as his or her enduring guardian to exercise the powers at law or in equity of a guardian if the person who makes the appointment subsequently becomes mentally incapacitated, in that event, to consent or refuse consent to the medical or dental treatment of the person, except where the person has a medical agent available and willing to act in the matter.
Many people have enduring powers of guardianship sitting in a drawer which they might expect to be valid, however an obscure provision of SA Act 12 of 2013 provides "A provision of such an instrument appointing an enduring guardian of a kind contemplated by section 6 or 12(1) of this Act will be taken to be void and of no effect."
Advice, explanation and creation of appropriate documents may be necessary in the management of your affairs, or if you were previously acting as a guardian appointed under such an instrument.