Final answer:
The nurse should contact the office of the public guardian and trustee when a patient is unable to make their own medical decisions and has no family.
Step-by-step explanation:
When a patient is incapable of making their own decisions regarding treatment and does not have any family, the nurse should contact the office of the public guardian and trustee. This is the entity often responsible for making decisions for individuals who lack the capacity to make their own medical decisions and have no one else to represent them. They are legally designated to act in the best interest of the incapacitated person. The most responsible physician can provide medical insight but does not typically hold the authority to make legal decisions on behalf of the patient. Furthermore, the patient's closest friend, while possibly understanding the patient's wishes, may not have the legal standing to make healthcare decisions unless legally documented. Similarly, the patient's social worker can assist with the coordination of care and support decision-making but would not be the decision-maker.