The effect of bispectral index-controlled sedation on postoperative cognitive health in elderly patients with spinal anesthesia undergoing elective total knee arthroplasty: randomized, blinded study

Background Postoperative cognitive dysfunction (POCD) commonly affects elderly patients, but the impact of BIS-guided sedation during elective orthopedic surgery under spinal anesthesia remains unclear. The aim was to compare BIS-controlled versus standard clinically guided sedation on POCD in elderly patients undergoing elective knee arthroplasty. Methods This was a prospective, patient- and outcome assessor-blinded, randomized controlled clinical study. Participants were randomized into two groups: BIS-targeted sedation (BIS group > 70) and standard clinical sedation (non-BIS group). All patients received the same anesthetic and analgesic. The primary outcome was the change in cognitive function over time. Cognitive function was assessed four times using the Addenbrooke’s Cognitive Examination–Revised (ACE-R) questionnaire. Higher scores indicate better cognitive performance. The emotional status was evaluated two times using the Hospital Anxiety and Depression Scale (HADS) . Results Ninety-two patients (46 per group) were included in the final analysis. No statistically significant differences in total ACE-R score were found between the two groups at any time point ( p > 0.05). Within the BIS group, total ACE-R scores were significantly higher on postoperative day (POD) 90 than preoperatively (PO) (87 (65–96) vs. 92 (70–98), p = 0.007). In the non-BIS group, total ACE-R scores increased significantly at several time points: from PO to 30 POD (87 (48–96) vs. 90.5 (40–98), p = 0.007), from PO to 90 POD (87 (48–96) vs. (91 (40–99), p < 0.001), and from 2 to 30 POD (88 (45–98) vs. 90.5 (40–98), p = 0.005). Significant decline in the number of patients experiencing probable anxiety at 30 POD compared with PO in both groups (BIS 28.3% to 2.2%, p = 0.004; non-BIS 32.6% to 8.7%, p = 0.015). Conclusions This study did not demonstrate superiority of BIS-controlled sedation compared to clinically guided sedation with regard to cognitive outcomes. Further studies are needed. Trial registration ClinicalTrials.gov (NCT06241859, January 28, 2024)