Effect of Intraperitoneal Ropivacaine on Visceral Pain After Laparoscopic Gastrectomy

Postoperative pain is a common adverse reaction after laparoscopic gastrectomy. Insufficient analgesia can cause severe stress response,affect the recovery of postoperative gastrointestinal function, increase the incidence of postoperative complications and prolong the length of hospital stay. Although laparoscopic surgery significantly reduces postoperative pain compared to traditional open surgery, the management of postoperative pain remains a challenge. Postoperative pain after laparoscopic surgery is mainly divided into three parts: incision pain(somatic pain component), deep abdominal pain (visceral pain component) and shoulder pain (referred pain component). In a prospective study, Blichfeldt-Eckhardt et al. found that visceral pain accumulated in the first week after surgery was identified as an independent risk factor for unexplained chronic pain at 12 months after surgery, and visceral pain was the only pain component that was independently and significantly associated with chronic unexplained pain at 12 months after surgery .

Visceral pain is generally defined as pain caused inside the body, but is usually caused by excessive contraction, stretching, or ischemia of the walls of internal organs . In contrast to pain signals originating from the skin,pain originating from the viscera is described as dull and diffuse, often poorly localized, and can be distant from its origin.Visceral pain is considered more unpleasant and frightening than somatic pain.

Therefore,relieving the visceral pain is of great significance for patients' postoperative emotional experience, functional recovery and reducing the formation of long-term chronic pain. However, there is no clear clinical consensus on relieving visceral pain by now, so effective clinical methods to relieve visceral pain need to be explored urgently.

Intraperitoneal spraying local anesthetics is a simple and inexpensive method, which has been proved to be a safe and effective way to reduce the use of opioid and postoperative pain score in randomized controlled trials and Meta-analysis of various surgical types such as laparoscopic cholecystectomy , laparoscopic appendectomy , laparoscopic gynecology and so on. Intraperitoneal spraying local anesthetics is a type of topical anesthesia.Local anesthetics produce local anesthesia by acting on nerve endings on the surface of the visceral organs.Visceral organs mainly transmit nociceptive signals through the vagus nerve and spinal nerve, among which the spinal nerve mainly transmits mechanical stimulation signals, while the vagus nerve mainly transmits chemical stimulation signals. Arman Kahokehr et al. found that intraperitoneal spraying local anesthetics during colectomy may reduce postoperative pain by blocking intra-abdominal vagus nerve signals. At the same time, it inhibits the corresponding neuroendocrine stress pathway, thus resulting in behavioral benefits. However, it does not separately evaluate the different pain components of patients after surgery.

At the same time,the effect of intraperitoneal spraying local anesthetics is still controversial and many studies lack evaluation of postoperative recovery quality,so this technique has not been widely used in clinical practice. Schipper IE et al. spray 20ml 2.5% bupivacaine into the abdominal cavity during laparoscopic gastric bypass surgery, and the test results indicated that the experimental group did not significantly reduce postoperative pain or opioid use, and the use of antiemetic drugs and the length of hospital stay were not significantly reduced.A review in 2021 included 85 clinical trials of intraperitoneal spraying local anesthetics during laparoscopic cholecystectomy, found that intraperitoneal spraying local anesthetics could reduce pain for up to 24 hours in patients undergoing laparoscopic cholecystectomy. However,none of these trials provided postoperation follow-up information and evaluation of postoperative recovery quality.

In this study, pain types are assessed independently to explore whether intraperitoneal spraying local anesthetics could reduce visceral pain by blocking splanchnic nerve afferents. This study will use ropivacaine, the most commonly used long-acting amide local anesthetic, which has low toxicity and an effective acting time of about 4-6 hours.This study set up multiple time points after surgery to evaluate the visceral pain and recovery quality of patients,in order to explore whether early postoperative pain control can slow down or block the formation of postoperative chronic pain, and systematically evaluate the effect of intraperitoneal spraying local anesthetics on the postoperative recovery quality of patients.In a meta-analysis Sparreboom CL et al. found that patients with postoperative anastomotic leakage had significantly higher levels of IL-6 and TNF-α in abdominal drainage fluid at 24h after surgery than those without anastomotic leakage, but this significant change was not observed in blood samples.Wiik et al. reported that inflammatory cytokines are more widely released into the abdominal cavity after abdominal surgery compared with systemic responses,which may be due to the secretion of these cytokines by lymphocytes and monocytes at the site of anastomotic leak.Inflammatory factors are not only related to postoperative anastomotic leakage, but also closely related to the occurrence and development of postoperative pain.Inflammatory stimulation or tissue damage stimulates a cytokine cascade that ultimately triggers the release of mediators that cause inflammatory pain. Immune cells release inflammatory factors such as IL-6 and TNF-α, and induce prostaglandin synthesis and enhance TRP and Nav channel activation through a series of signal transduction pathways, thus inducing inflammatory pain in vivo.Therefore, we plan to detect the inflammatory factors IL-6 and TNF-α in the abdominal drainage fluid at 24h after surgery,to explore the effect of Intraperitoneal spraying local anesthetics on the postoperative abdominal drainage fluid related inflammatory factors, and to evaluate its influence on the recovery of postoperative gastrointestinal function further.

The anesthesia induction protocol for this study includes intravenous titration administration of propofol at a rate of 0.5mg/kg/min, sufentanil 0.3ug/kg, and cisatracurium 0.2mg/kg. Anesthesia is maintained with propofol, remifentanil cisatracurium and sevoflurane to maintain the patient's blood pressure at ±20% of the basic blood pressure and BIS between 40 and 60. The first dose of analgesia and antiemetic (0.3ug/kg sufentanil + 5mg dezocine + 0.25mg palonosetron hydrochloride) is given half an hour before the end of surgery. Before closing the abdominal cavity after abdominal irrigation, 20ml of 0.5% ropivacaine or an equal volume of normal saline is uniformly sprayed onto the surgical area using an endoscopic instrument channel. After skin closure, 10ml of 0.5% ropivacaine is used for infiltration anesthesia at the incision site, and a venous analgesia pump is connected (3ug/kg sufentanil + dezocine 15mg+ palonosetron hydrochloride 0.5mg+NS 120ml). After the surgery, the patient is induced to spontaneous breathe and the tracheal tube will be removed, and then he is sent to the PACU for further observation. If the pain NRS score in the recovery room is greater than 4, a single injection of 5ug sufentanil will be administered until the NRS score is ≤4. When the patient achieve a Sterward score of 6 points, he will be returned to the ward.

Visceral pain is obvious and lasts for a long time in patients after laparoscopic gastrectomy. This study intends to include these patients in the study, and adopt ropivacaine, a local anesthetic with less cardiotoxicity and relatively long acting time,to provide further clinical data for the relief of postoperative visceral pain by intraperitoneal spraying local anesthetics.This study will also systematically evaluate the effect of intraperitoneal spraying local anesthetics on the postoperative recovery quality and the inflammatory factors in postoperative abdominal drainage fluid.