To the Editor.
—I read with interest the article by Dr Williams-Russo and colleagues1 regarding cognitive effects after epidural vs general anesthesia. However, since the overall effect on cognition is certainly most profound in the first few days after an anesthetic, it would seem imperative that the medications received by patients during that first week would need to be tightly controlled, and in fact they were not. For example, the epidural group received midazolam for sedation; the general anesthetic group did not. This drug is certainly capable of producing significant cognitive impairment, particularly in elderly patients, and this should have been considered. In addition, the type of postoperative analgesia was not controlled in the study. Again, medications that are routinely given for postoperative analgesia can have significant effects on cognition, and these too should have been controlled for if valid conclusions were to be drawn regarding the anesthetic technique