Effect of early regional anesthesia on postoperative cognitive function and the perioperative stress response in patients with hip fractures: a randomized controlled trial

Background Whether early application of anterior iliopsoas muscle space block (AIMSB) impacts postoperative cognitive function remains uncertain. This study aimed to compare the incidence of postoperative delirium (POD) among patients who received AIMSB at different time points. Methods This prospective, single-blind, randomized trial enrolled 79 patients aged ≥65 years hospitalized for primary unilateral total hip arthroplasty (THA) due to hip fractures (December 2022 to February 2024). All patients underwent spinal anesthesia. Participants were randomized to receive AIMSB either the day before surgery (D group, n  = 39) or one hour before surgery (H group, n  = 40). The primary outcome was the incidence of POD within 7 days. Secondary outcomes included postoperative pain scores at specified intervals, time to first rescue analgesia, cumulative opioid consumption, motor function recovery time, hospital discharge time, sleep quality, Quality of Recovery-15 (QoR-15), and laboratory tests. Results Seventy-six patients completed the study per protocol. POD incidence was 8.1% (3/37) in the day-before-surgery group and 12.8% (5/39) in the hour-before-surgery group (risk difference, −4.7%; 95% CI [−18.4% to 9.0%]; P  = 0.71). At 6 hours postoperatively, resting pain scores (2.46 ± 0.80 vs. 2.95 ± 1.21, P  = 0.043) and movement-evoked pain scores (3.24 ± 0.83 vs. 3.79 ± 1.17, P  = 0.021) were lower in the D group; however, these differences did not remain statistically significant after correction for multiple comparisons. In an exploratory post-hoc analysis, the IL-6 curve area under the curve was 0.895 (95% CI [0.784–0.998]) this finding requires prospective validation. Conclusions Among elderly patients undergoing THA for hip fracture, performing AIMSB one day preoperatively, compared to one hour preoperatively, did not significantly reduce the incidence of POD. An exploratory analysis suggested a transient early postoperative pain benefit, that did not survive multiplicity correction. These findings warrant further investigation in larger, appropriately powered trials.