Sedation depends on the dog. Different Vets have different techniques. The worst thing is not a false negative, but a false positive, which can happen in well muscled breeds. This is the major critique of OFA technique. With the right sedation or board, one with good muscle relaxation, you shouldn't need to induce and maintain. I have seen relaxed dogs tolerate the procedure without sedation also. Typically, at least a mild sedative is used.