Anaesthetic depth monitoring decreases the incidence of postoperative delirium in elective non-cardiac surgical patients receiving intravenous patient-controlled analgesia: A prospective observational study

Background: To identify the impact of processed electroencephalogram (pEEG)-guided anesthesia on postoperative delirium (POD), postoperative analgesic requirements, and the incidence of postoperative nausea/vomiting (PONV) in the elective non-cardiac surgical patients with intravenous patient-controlled analgesia (IVPCA) in the wards. Methods In this prospective observational study, the anesthesiologists were free to use M-Entropy™, an pEEG device, to monitor the depth of anesthesia intraoperatively during the period (September 2015 ~ February 2018). Acute pain service team assessed the analgesic/side effects of IVPCA and POD at least twice daily for 3 days postoperatively. POD was screened by Nursing Delirium Screening Scale (NuDESC) (0–10). A psychiatrist or neurologist was consulted to confirm suspected POD if NuDESC ≧ 1. Pain severity was measured by an 11-point verbal numerical rating scale (0–10). Results A total of 1178 patients ( ≧ 60 years) were enrolled and divided to Entropy (749 patients) vs. non-Entropy group (429 patients). Multivariate logistic analysis showed that age ≧ 70, surgical types and the POD incidence were independent predictors for group differences (multiple odds ratio and 95% confidence interval: 9.49, 6.99–12.89; 0.47, 0.35–0.63; 0.11, 0.06–0.21). The POD incidence in Entropy group (2.2%, 17 patients) was significantly lower than that in non-Entropy group (6.7%, 29 patients) ( p  < 0.001). However, pEEG-guided anesthesia did not affect the duration and phenomenological characteristics of POD. In addition, intraoperative pEEG-guided anesthesia did not reduce total daily morphine dose of IVPCA, the incidence of PONV and inadequate postoperative pain management. Conclusions Processed EEG-guided anesthesia decreased POD incidence in IVPCA patients undergoing elective non-cardiac surgery returning to the ward. In addition, it did not reduce postoperative pain severity, postoperative analgesic requirements and postoperative nausea/vomiting. More research is needed to investigate the effects of pEEG-guided anesthesia on POD and the other postoperative conditions.