A surgical nurse told me about a medical negligence case that was able to use the res ipsa loquitur principle. A doctor performed a hysterectomy on a woman, and a major nerve was injured and caused paralysis of her left arm.
To show medical negligence and use res ipsa loquitur, she needed expert medical testimony to show that her injury was likely caused by negligence. She would need to show that the surgeon was under control of the surgery. And then she would need to show that she had no part in the injury - easy to show if the person is unconscious.
Unless the medical case is very complicated, using res ipsa loquitur is pretty straight forward. The important thing is to get a good medical expert to testify for you.