I'm writing a book where the main character is a cyborg, it's going to be a hard-science book and my idea is like a brain in a jar with the intact brain within a structure that pumps artificial blood to the brain, how could this device pump blood to the brain if (the brain) has no carotid arteries? Perhaps intravenously? But those needles would need to be changed regularly right? (I'm new to this site I hope I'm doing this right >.<)
Assuming you are asking for a replacement to the carotid artery: Artificial blood vessels are one possibility. Expanded polytetrafluoroethylene can be used to create blood vessels of both short and long diameters. This material is inert and does not degrade.