Ketamine and the At-Risk Brain.

Abstract

Postoperative cognitive dysfunction and delirium are undesirable consequences of surgery and anesthesia that regrettably do not have consistent predictive markers. Nor do they have reliable prophylactic or treatment methodologies. In an effort to better understand how anesthetic drugs alter the rate of postoperative delirium, Chang et al explore how patients with preoperative cognitive impairment respond to the influence of intraoperative ketamine. Patients aged 65 or older presenting for spine surgery lasting over three hours were assessed and divided into those with and without baseline cognitive impairment. Both groups either received intraoperative ketamine or did not. All patients who received intraoperative ketamine demonstrated an increase in power spectral density via electroencephalographic assessment. However, patients with preoperatively established cognitive impairment displayed a significantly diminished electroencephalographic response to ketamine. Furthermore, this subgroup also suffered an increased incidence of postoperative delirium. What is the interpretation of this finding? An accompanying editorial elegantly describes how disorders of cognition result from both predisposing and precipitating factors. In this case, patients with known cognitive impairment were more likely to endure delirium when exposed to ketamine. Is it possible that ketamine and other drugs could be used as agents to stratify cognitive risk? Should we definitively avoid such drugs as potentiators of cognitive dysfunction? A variety of contextual limitations must be entertained when interpreting the results of this study as summarized in this infographic. These are also elaborated in greater detail in both the primary article as well as its attendant editorial. The reader is encouraged to review both in their entirety for an in-depth scope of understanding.