Power of Attorney is a series of documents that permit others to take charge of your horse if you are not able to do so. This includes making medical decisions concerning treatment, costs, and euthanasia. Have a long talk with people about your desires for your horse and ask someone who shares your outlook to take the responsibility. This could include the stable manager if you board, your instructor, riding friend, or veterinarian.
You can download a Power of Attorney form here: (https://www.usrider.org/travel-safety/transportation-info