Effects of Calot's Triangle Block for Postoperative Analgesia in Patients Undergoing Laparoscopic Cholecystectomy: a Prospective, Randomized, Double-blind, Controlled, Clinical Trial

Chronic pain after laparoscopic cholecystectomy (LC) is a common complication with an incidence ranging between 3-56%. In many cases, however, the cause chronic pain after LC remains unknown and visceral hyperalgesia and central sensitization have been suggested to be part of the pathophysiology. So the purpose of this study is to determine whether Calot's Triangle Block (CTB) combined with patient controlled intravenous analgesia (PCIA) is superior to PCIA in reducing the incidence of chronic pain after LC.

Laparoscopic cholecystectomy (LC) is currently regarded as the gold standard treatment for symptomatic gallstone disease. Compared with open cholecystectomy, LC benefits include less postoperative pain, reduced analgesic consumption, and earlier discharge. However, besides the advantages mentioned above, there are exist complexity and diversity of the acute pain after LC, which consists of a somatic, a visceral and a referred pain component. Meanwhile, our team also found many LC patients experience visceral pain after surgery. According to epidemic research show that chronic pain after LC is a common complication with an incidence ranging between 3-56%. Several reports have indicated that early postoperative pain has been shown to be a significant risk factor of chronic pain. In many cases, however, the cause chronic pain after LC remains unknown and visceral hyperalgesia and central sensitizationhave been suggested to be part of the pathophysiology. To reduce the incidence of chronic pain after LC, so we conduct the randomized controlled trial to investigate whether calot's triangle block combined with PCIA is superior to PCIA in reducing the incidence of chronic pain after LC.

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. All potentially eligible participants will be asked to give written informed consent before they are enrolled in this study. This study is a prospective, randomized, double-blind, controlled clinical trial guided by the standard of good clinical practice (GCP), and eligible participants are divided into two groups: group CTB and group PCIA, and primary assess the outcomes of the incidence of chronic pain after LC and the intensity of acute pain after LC.

Participants in group CTB will receive a single injection of ropivacaine in calot's triangle before surgical dissection combined with PCIA post-operatively.

Participants in group PCIA will receive a single injection in calot's triangle with normal saline before surgical dissection and PCIA post-operatively.

The primary outcome of this study is the incidence of chronic pain after LC.

The secondary outcomes of this study are acute post-operative pain, moderate-severe pain, rescue medication and adverse events associated with the post-operative analgesia.

This study will be conducted under the supervision of an independent auditor. Every week, the auditor checked the data of the participants the day after the surgery was conducted. Assessment of pain intensity and prognostic outcomes must be confirmed by the auditor in sample population. When there is disagreement between surgeon and anesthesiologists in evaluating the prognosis of patients, the auditor must solve this disagreement by discussion with evaluators. Data will be double-entered by two statisticians with limitation of access and locked during statistical analysis.

Eligibility Criteria:
Inclusion Criteria:

* men or woman over 18 the years and younger than 65 years old who will receive selective laparoscopic cholecystectomy.

Exclusion Criteria:

* age below 18 years or over 65 years
* American Society of Anesthesiologists grade III or greater
* Diabetes
* chronic pain of any kind other than gallbladder disease
* allergic to local anesthetics
* cognitive impairment or communication problems
* peptic ulcer
* received opioids、NSAID or tranquilizers (treatment for over 1 wk before the cholecystectomy)
* history of alcohol or drug abuse
* the operation was converted to an open procedure
* gangrenous cholecystitis
* common bile duct exploration or insertion of a T-drain
* other invasive procedures
* severe hepatic or renal impairment
* post-operative severe complications(e.g. pyogenic infection)