A client in the intensive care unit (ICU) is in a comatose state following a traumatic brain injury and sustained intracranial pressure leading to death. They present with no brain-stem reflexes, no brain activity on 3 previous electroencephalography scans, and cannot breath on their own. Therefore, the health care provider (HCP) has determined a clinical diagnosis of brain death. The substitute decision maker of the client is demanding more treatment options and procedures. 

 Which ethical principle should guide how the nurse interacts with the substitute decision maker?