Abstract: Objective To compare the effect of single -injection sciatic nerve block combined continuous femoral nerve block with continuous femoral nerve block on incidence of postoperative delirium in older patients. Methods A prospective, random study was conducted in patients who underwent total knee replacement. Baseline cognitive function was assessed using Mini-Mental State Examination scores in the day before operation. Postoperative delirium was measured using the Confusion Assessment Method postoperatively. All of the patients receiveda spinal anesthesia and light propofol sedation during operation. Guided bya nerve stimulator, sciatic nerve block combined continuous femoral nerve block was performed in experimental group and continuous femoral nerve block was performed in control group after spinal anesthesia. All of the patients received patient-controlled analgesia as adjuvant analgesia. In addition, pain levels(using numerical rating scale scores, NRS) and opioid use were compared in two groups. Results 97 patients were studied. The overall incidence of postoperative delirium was 11.3% in 72h after operation. Incidence of postoperative delirium in experimental group was lower than control group(4.1% vs. 16.7%, P=0.028). There was significantly less NRS in experimental group comparing control group at rest 24,48 and 72h after surgery( P<0.01).The postoperative sufentanil consumption and PCA button press times in control group were more than that of experimental group(P <0.01) at 72h after operation. Conclusion Single-injection sciatic nerve block combined continuous femoral nerve block reduces the incidence of postoperative delirium.

Key words: delirium, nerve block, ropivacaine