My cat had her hind leg amputated a week ago. She has been on Buprenorphine. The last 5 nights she has been waking up several times a night crying out, the high pitch sound cats make when they fight, then she thrashes around, sometimes moans a little and then she's done. The vet has never heard of this before. She put a Fentanyl patch on her yesterday hoping these behaviors do not continue. Has anyone ever experienced this or know of anyone who has? It's been really hard to watch. She is doing really well otherwise.