Between 10 and 20% of the Western population suffer from gallstones. When a surgical operation (cholecystectomy) is necessary, the removal of the gallbladder is done by laparoscopy in 95% of cases. The risk of having to undergo this operation increases with age and on average women are twice as likely as men to have to undergo surgery. In Belgium, only 4% of these laparoscopic cholecystectomies are performed as one day hospitalization. Although this operation is considered a minor surgery, patients sometimes report intense postoperative pain that may encourage them to spend a night in the hospital. Better management of postoperative pain could increase the number of outpatient procedures. A large individual variability in pain intensity is observed after this surgical procedure. Three types of pain can be associated with this surgery: parietal pain secondary to the incisions of the wall necessary for the introduction of the surgical instruments; deep visceral pain, difficult to localize and secondary to surgical trauma in the area of dissection of the gall bladder; and scapular pain, a projected pain secondary to the irritation of the diaphragm by CO2-pneumoperitoneum. The temporal characteristics and intensity of these three types of pain are different. Some report a predominance of parietal pain, while for others visceral pain is most intense.

The Transversus Abdominis Plane (TAP) block is a loco-regional analgesia technique that consists of infiltrating a local anesthetic solution between the plane of the transversus abdominis muscle and the internal oblicus muscle, laterally at the level of the triangle of Petit. The sensory nerves of the abdominal wall pass through this plane. This technique produces long-lasting analgesia, between 24-36 hours. Only the nerves responsible for the innervation of the abdominal wall are blocked by this infiltration. The metameric extension of parietal analgesia varies from one study to another, especially depending on the site of infiltration. After posterior TAP block, parietal analgesia concerns the infra-umbilical abdominal wall, but can reach in some cases the dermatome T-8. When the surgery involves the supra-umbilical abdominal wall, the TAP block is performed at the subcostal level to block the nerve branches T-6 to T-10. Infiltration is then performed between the transverse muscle and the rectus abdominis at the lateral end of this muscle.

Several studies have evaluated the efficacy of TAP block for analgesia after laparoscopic cholecystectomy. Controversial results have been reported. These controversies can be explained in part by the type of TAP block used: lateral versus subcostal approach which appears more appropriate for laparoscopic cholecystectomy (supra-umbilical parietal incisions). In addition, effective multimodal analgesia, a recommended good medical practice, is not always used in these studies. This strategy, by effectively reducing postoperative pain, may make the clinical utility of TAP block irrelevant. Finally, in case of predominance of parietal pain on visceral pain, the clinical relevance of the TAP block should be objectified. In the opposite case (predominance of visceral pain), TAP block would be much less effective.

2.2 Purpose of the study. The purpose of this study is to evaluate the analgesic efficacy of TAP subcostal block after laparoscopic cholecystectomy. The effectiveness of the TAP block will confirm the importance of the parietal pain component after this type of surgery. Decreases in postoperative pain and postoperative opioid consumption, possibly associated with a decrease in morphine side effects (nausea, vomiting, sedation, fatigue), may be conducive to the development of outpatient laparoscopic cholecystectomy.

2.3 General description. This randomized double-blind placebo-controlled study will include two groups of 20 patients: the TAP block will be performed in a group using a local anesthetic solution (levobupivacaine \[Chirocaine®\] 0.375% Adr 1/200000) in the " treatment " group and with saline Adr 1/200000 in the control group.