The nurse should request the client's son, who has a durable power of attorney, to sign the client's informed consent. A durable power of attorney is a legal document that allows an individual to appoint someone to make decisions on their behalf in the event that they become unable to do so. If the client has dementia and is unable to provide informed consent for the procedure, the individual with a durable power of attorney has the legal authority to make decisions on their behalf.

The other individuals are not the appropriate person to sign the client's informed consent. The client's sister [b] and daughter [c] may be involved in the client's care and decision-making, but they do not have the legal authority to provide informed consent on behalf of the client unless they have been designated as such in a legal document. Advance directives [d] are legal documents that allow individuals to communicate their wishes about medical treatment and end-of-life care, but they do not grant decision-making authority to another individual.