Though there are differences from region to region, there are also some consistencies. One consistency is that requests for MAID cannot be made in advance. This would rule out the possibility of including such a request in a health care directive, as such documents are made in advance in anticipation of a day in which a patient can no longer make decisions.
The guidelines contemplate a specific situation in which a patient is "suffering from a serious and incurable illness, in an advanced state of irreversible decline and experiencing constant and unbearable physical or psychological suffering which can't be relieved in a manner acceptable to the patient". This ties in with the requirement for the patient to have mental capacity to make the request for MAID. Given that an advance health care directive is used only when a patient does not have mental capacity to make decisions, the requirement for mental competency rules out the use of an advance health care directive.
Time will tell how these guidelines work out.