We read with great interest the recent article by Brown et al. regarding the impact of Bispectral Index (BIS)–guided sedation on the incidence of postoperative delirium during spinal anesthesia for spine surgery compared with BIS-masked general anesthesia. We appreciated the originality and efforts of the authors to clarify a still controversial topic such as the connection between depth of the hypnotic component of anesthesia and postoperative delirium. Nevertheless, after careful reading of the trial and its conclusions, we would like to address some critical input to the authors.

First, in the “Materials and Methods” section, the authors report that they achieved spinal anesthesia using intrathecal bupivacaine or lidocaine. Spinal anesthesia with lidocaine carries the risk of transient neurologic symptoms. Transient neurologic symptoms constitute an acute pain syndrome that could exacerbate postoperative pain and thus increase the incidence of postoperative delirium. In addition, acute postoperative urinary retention after spinal...

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