As I remember, when used for ME/CFS it is given in a low dose, very slow infusion which apparently prevents the dissociative side-effects. To quote from a letter by Dr. Jay Goldstein (sorry, I don't have a link): I've read about this. Dr. Jay Goldstein found that it had remarkable effects on ME/CFS patients, but I think that the challenge was getting lasting results. If I do try it, I'll go over all these aspects with the anesthesiologist beforehand. Thanks for sharing your experience with it.