Postoperative delirium is a common complication in clinical surgery. It has been reported that it can increase postoperative morbidity and mortality and lead to decreased functional and cognitive abilities. The aim of this study was to investigate the effect of ultrasound-guided bilateral rectus sheath blocks (RSB) on postoperative delirium in elderly patients undergoing laparoendoscopic single-site surgery (LESS) A double-blind, randomized controlled trial was conducted with 320 patients, aged 65-80 years, ASA I-III, who were scheduled to undergoing LESS in our hospital were selected, the patients divided into Group R and Group G by random number table method, with 160 patients in each group. Group R was subjected to a bilateral RSB under ultrasound guidance after general anesthesia, each side was given 0.5% ropivacaine 10 ml. Group G received simple general anesthesia.

The mini-mental State Examination was used to assess all the patients' primary cognitive status one day before surgery. Perioperative variables were recorded to be compared. The investigators used the visual analog scale to assess patients' pain degree with postoperative, using confusion assessment method to assess whether patients experienced delirium.

1. Study design and setting 320 elderly patients undergoing LESS surgery under general anesthesia (including inguinal hernia and cholecystolithiasis), gender, aged 65-80 years, American Society of Anesthesiologists (ASA) physical status I-II. Exclusion criteria: MMSE of 1 day before surgery < 27, communication and dysfunction (e.g., vision, hearing), cerebrovascular history, local anesthetic allergy, opioid allergy, puncture site infection, abnormal clotting.
2. Subjects Patients were allocated randomly to R group (bilateral rectus abdominis sheath blocks combined with the general anesthesia group) and G group (the simple general anesthesia group) according to computer-generated random number table. All patients and an investigator who was responsible for follow-up during 48 postoperative hours were blinded to the randomization groups. In addition, during preoperative visits, the investigators instructed patients how to use the patient-controlled intravenous analgesia (PCA) device for pain management, as well as how to use the visual analog scale to evaluate pain at rest and while coughing. All the bispectral index (BIS) value in the present study was maintained between 40 and 60 during surgery. All patients voluntarily signed informed consent.
3. General anesthesia Patients were monitored by electrocardiogram, pulse oximetry and non-invasive blood pressure (one measurement every 3 min) while entering operation room. A radial artery catheter was also placed for invasive arterial pressure and blood gas monitoring. The induction of general anaesthesia was performed intravenously with sufentanil 0.5 µg/kg, propofol 1-2 mg/kg, and rocuronium 0.6 mg/kg. Endotracheal intubation was performed with a double-lumen tube. Sevoflurane was wsed at a minimal alveolar concentration (MAC) of 0.8-1, remifentanil and propofol were used for the maintenance. Fluid management was at the discretion of the attending anaesthesiologist.

Inclusion Criteria:

• Aged 65 to 80 years male and female
• Scheduled for elective single-incision laparoscopic cholecystectomy
• The patients volunteered to participate in the study and signed the informed consent

Exclusion Criteria:

• Preexisting neuropathy
• Coagulopathy
• Local skin infection
• Hepatic, renal or cardiorespiratory failure
• Local anesthetic allergy
• Pregnancy
• Complications of gallstone with gallbladder perforation
• Diffuse peritonitis
• Acute pyogenic cholangitis