The effect of sedation methods on early postoperative cognitive decline in patients undergoing hip fracture surgery with spinal anesthesia: a prospective cohort study

PURPOSE: Early postoperative cognitive decline is common in elderly patients undergoing hip fracture surgery and may contribute to delayed recovery and diminished long-term independence. Although spinal anesthesia is associated with reduced systemic cognitive burden, intraoperative sedation remains necessary and may influence neurocognitive outcomes. Dexmedetomidine and ketamine are sedative agents with proposed neuroprotective properties; however, their comparative cognitive safety in the context of spinal anesthesia remains poorly understood. Thus, our study aim to compare early postoperative cognitive outcomes between intravenous dexmedetomidine and ketamine used for intraoperative sedation during spinal anesthesia in elderly patients undergoing hip fracture surgery. METHODS: In this prospective observational cohort study, elderly patients undergoing hip fracture surgery under spinal anesthesia were enrolled to compare the effects of dexmedetomidine and ketamine on early postoperative cognitive function. The primary outcome was MMSE score on postoperative days 1 and 3. Secondary outcomes included Clock Drawing Test (CDT) scores, length of stay, and perioperative complications. Cognitive assessments were conducted preoperatively, and postoperatively on days 1 and 3 by blinded clinicians. RESULTS: Eighty-two patients [dexmedetomidine (n = 41), and ketamine (n = 41)] were analyzed. Baseline demographics and clinical characteristics were comparable. Postoperative MMSE scores were significantly higher in the dexmedetomidine group on both day 1 (21.4 ± 4.0 vs. 17.1 ± 5.4; p < 0.001) and day 3 (21.9 ± 3.9 vs. 17.6 ± 5.7; p < 0.001). Both groups exhibited a decline in MMSE scores on postoperative day 1, with partial recovery by day 3; scores remained significantly lower than baseline levels (p < 0.01 for both groups). The magnitude of MMSE decline was statistically smaller in the dexmedetomidine group compared to the ketamine group (p < 0.001). Similarly, CDT scores declined from baseline on postoperative day 1, and showed moderate improvement by day 3. However, no significant differences were observed in CDT scores or complication rates between groups. Sedation depth and intraoperative analgesia were comparable, aside from transient differences at the 5th minute post-sedation. CONCLUSION: Dexmedetomidine was associated with less early postoperative MMSE decline compared with ketamine in elderly patients undergoing hip fracture surgery under spinal anesthesia. These findings reflect differences in early postoperative cognitive trajectory rather than established postoperative cognitive dysfunction. TRIAL REGISTRATION: Date of Registration: 02/02/2023 (Retrospectively registered). https://clinicaltrials.gov/study/NCT05737459.