My doctor said it would be to dangerous to sedate me because of my brain injury is this true and why?

Could be!: General anesthesia and IV sedation is usually safe in most. But some people have conditions that make it risky. The key is what needs to be done. In an emergency life and death situation, you may get it anyway because the benefit outweighs the risk. With lesser procedures, local anesthesia may be safer and enough to manage your pain. Discuss again with doc and find out what your options are.