Total knee replacement (TKR) is among the most commonly performed orthopedic procedures, and a six-fold increase in the number of TKR cases world-wide is projected within a decade as the aging of the populations . As the number of the TKR procedures increases, various approaches increasing the satisfaction and comfort of the patient and the surgeon are of interest in order to provide improved pain management, in-hospital stay, and recovery with the development of modern anesthesiology and pain management techniques.This study aimed to investigate the clinical effect of ultrasound-guided high fascia iliaca compartment block(H-FICB) in patients undergoing knee arthroscopy and to compare it with the normal method which is femoral nerve block combined with a sciatic nerve block to choose the better way. A double-blind, randomized controlled trial was conducted with 44 patients, aged 18-65 years, ASA I-III, who were scheduled to undergo arthroscopic knee surgery in our hospital were selected, the patients were divided into Group A and Group B by random number table method, with 22 patients in each group. Group A was subjected to the H-FICB under ultrasound guidance before general anesthesia, given 0.375% ropivacaine+0.5ug/kg Dexmedetomidine 30 ml. Group B was subjected to the H-FICB under ultrasound guidance before general anesthesia, given 0.375% ropivacaine+1ug/kg Dexmedetomidine 30 ml.

The mini-mental State Examination was used to assess all the patients' primary cognitive status one day before surgery. The initial acting time and the degrees of sensory block and motor block were recorded after the nerve block was completed. Perioperative variables were recorded to be compared. The investigators used the visual analog scale to assess patients' pain degree with postoperative, recorded the occurrence of adverse events such as postoperative nausea and vomiting(PONV), delayed emergence from anesthesia, and respiratory depression. The confusion assessment method was used to assess whether patients experienced delirium.

1. Study design and setting 44 patients undergoing arthroscopic knee surgery under general anesthesia, gender, aged 18-65 years, American Society of Anesthesiologists (ASA) physical status I-III. Exclusion criteria: 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 A group (the Modified Fascia Iliaca Compartment block+0.5ug/kg Dexmedetomidine ) and B group (tthe Modified Fascia Iliaca Compartment block+1ug/kg Dexmedetomidine) according to a 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 on 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 the operation room. A radial artery catheter was also placed for invasive arterial pressure and blood gas monitoring. The induction of general anesthesia 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 used 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 18 to 65 years male and female Scheduled for elective arthroscopic knee surgery 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