Which would you rather administer to an animal with a broken pelvis that needs to be positioned for radiographs: a sedative, a local anesthetic, a general anesthetic, or an analgesic? What would be the advantages or disadvantages of each type of drug in this situation?
Many sedatives do not have analgesic activity. While the animal appears to be resting comfortably, as soon as you begin to move the animal, it will respond (biting, moving, vocalizing) because the sedative did nothing to reduce the perception of pain. This is a potentially dangerous situation because the animal appears to be without pain, but is merely in a state of feeling relaxed and sleepy. A local anesthetic is not going to cover all the areas that to be anesthetized. A general anesthetic would decrease all perception, including perception of pain for the entire body. However, a general anesthetic by itself would allow wind-up to occur in the spinal cord, and there is more of a risk of using a general anesthetic than some of the other drugs. An analgesic at doses high enough to suppress visceral pain would probably be the best choice.