Discussion
delirium, postoperative delirium, metabolic derangements, cognitive dysfunction
In the context of preventing postoperative delirium and cognitive dysfunction in elderly patients, we found that patients who received dexmedetomidine had the lowest incidence of postoperative delirium and cognitive dysfunction compared to ketamine and placebo. A single pre-induction dosage of dexmedetomidine reduced the incidence of postoperative delirium by 32% and cognitive dysfunction by 62% compared to the placebo. However, ketamine use increased the risk of postoperative delirium three times and cognitive dysfunction 4.5 times more than placebo.Notably, abnormally high levels of pro-inflammatory markers, abnormal neurotransmitter levels, physiologic stresses, and metabolic derangements are the most important pathophysiologic contributors to postoperative delirium [The results from this study are generally in line with a previous meta-analysis of 108 RCTs on delirium pharmacotherapy, which confirmed the effectiveness of dexmedetomidine in reducing the incidence of delirium in postoperative patients (OR 0.46, 95% CI 0.32–0.66, high strength of evidence) [Our study showed that ketamine raised the risk of postoperative delirium three times more than placebo. In line with our findings, Hollinger et al. [The results of our study showed that patients in the ketamine group had a long time to first postoperative request for analgesia and less postoperative nalbuphine requirement than the placebo and dexmedetomidine, which could be attributed to ketamine’s analgesic impact [Our research has some limitations. First, it is a single-center study with a small sample size limited to elderly patients scheduled for emergency surgery; therefore, it cannot be extended to all surgical patients. Second, the intraoperative hemodynamic data were collected but not analyzed because the study groups were not sufficiently powered to detect statistically significant changes in hemodynamic parameters. Third, the delirium assessment could only be done twice a day on a regular basis. This could contribute to an underestimation of the incidence of delirium; also, details on the duration and severity of delirium, as well as the treatment offered to delirium patients, were not gathered. Lastly, patients in the study underwent surgeries of several disciplines with greatly different postoperative treatments.In summary, a considerable body of evidence supports the use of a single pre-induction bolus of dexmedetomidine as a practical choice for preventing postoperative delirium and cognitive dysfunction in elderly patients undergoing emergency surgery.