The Effect of Continuous Femoral Nerve Block With Modulation of Depth of Anesthesia on Prognosis of Patients Receiving Total Knee Arthroplasty

The interaction of analgesia and sedation ot their effect on the prognosis of surgical patients still need to be elucidated.Currently, how to optimize intra-operative Analgesia and sedation to improve the prognosis of surgical patients is still a mystery.Intra-operative nerve block provided regional analgesia of the operated knee, which reduced the dosages of sedatives and analgesics.Based on a pilot study,the investigators found a decrease of post-operative adverse composite outcomes with the use of continuous femoral nerve block (2% versus 7%) ,therefore, the investigators postulate that general analgesia with lighter sedation in combination with peripheral nerve block could reduce the post-operative morbidity compared with deeper sedation.This randomized controlled trial is designed to test this hypothesis in patients receiving unilateral knee arthroplasty.

This study was approved by the institutional review board of the First Affiliated Hospital of Chongqing Medical University. The protocol design is in accordance with Consolidated Standards of Reporting Trials (CONSORT) statement.This study is designed as a randomized controlled trial to compare intra-operative continuous femoral nerve block combined with lighter anesthetic depth (group L) with deeper anesthetic depth (group D) monitored by bispectral index (BIS). All potentially eligible participants will be asked to give written informed consent before they are enrolled in this study.The following outcomes will be assessed:post-operative major complications (post-operative pulmonary infection,need of mechanical respiratory support,myocardio-infarction,deep venous thrombosis, pulmonary embolism, stroke, poor wound healing,all-cause post-operative death within 30 days).Secondary Outcomes included :acute post-operative pain assessed by visual analogue scale and dosages of rescue medications;Dosages of intra-operative vasopressors,anesthetics and analgesics;Life quality measured by EQ-5D questionnaire 3 months post-operatively;adverse events associated with the femoral catheter (displacement, infection, hematoma,drop-out of catheter).

Eligibility Criteria:
Inclusion Criteria:

* Men and women over the 18 years and younger than 80 years old
* Scheduled to receive selective unilateral knee replacement.

Exclusion Criteria:

* Bilateral knee replacement
* The secondary knee revision and knee surgery not interfering with articular joint cavity (wound debridement and suture)
* American Society of Anesthesiology (ASA) classification of anesthesia risk IV and V grade
* Body mass index higher than 35
* Coagulation dysfunction, which is assessed by activated partial thromboplastin time (APTT) higher than the upper limit by 10s; prothrombin time (PT) higher than the upper limit by 5s; International Normalized Ratio (INR) higher than 1.3, or any of criteria met above;
* Pre-operative hypoxia (SpO2\< 90% or PO2\<60 mmHg)
* Pre-operative hypercapnia (PCO2\> 50 mmHg)
* Local infection of puncture sites
* Neurological diseases and pre-operative psychological disorders
* Uncontrolled general infection
* Intra-operative cardiac arrest.