In regards to a DNR, can it be revoked by any reasonable SDM or do they also need to be POA? 

Answer 

Per the Do Not Resuscitate Training Bulletin (link)  “A paramedic will initiate CPR on a patient who has experienced respiratory or cardiopulmonary cardiac arrest when, c) the Substitute Decision Maker (SDM) has rescinded the Valid DNR Confirmation Form by stating he/she wants the patient to have CPR or d) there is confusion about who the SDM is and/or one or more people present the time demanding that CPR be initiated on the patient.  

 The training bulletin also defines SDM as a person who is legally authorized to give or refuse consent to a treatment on behalf of a person who is incapable with respect to the treatment.  

They do not need to be the POA. Under the Health Care Consent Act (1996) there is a hierarchy to consider when determining who the SDM would be, if the patient did not complete a Power of Attorney for Personal Care form while he/she was still capable. 

BLS,Do Not Resuscitate (DNR)

DNR, POA, SDM, VSA

Health Care Consent Act, 1996, S.O. 1996, c. 2, Sched. A https://www.ontario.ca/laws/statute/96h02 

Do Not Resuscitate (DNR) Standard. Issue Number 108 – version 1.0. November 2007.