1. Pain management is a crucial part of general anesthesia surgery. Nociception monitoring can help anesthesiologists better titrate the use of intraoperative analgesic drugs, especially the opioid.
2. Although a variety of nociception monitoring devices have been developed to date, there is not a specific monitoring indicator that serves as the "gold standard" to objectively guide analgesic management in general anesthesia.
3. The MGRNOX index, which is derived from electroencephalogram (EEG), is used to reflect the correlation between noxious stimuli and opioid analgesics in a state of general anesthesia by converting and quantifying the EEG signals collected by the instrument. However, no studies have so far verified the effect of the MGRNOX index-guided analgesic management of general anesthesia on the consumption of opioids in patients.
4. This study aims to explore the effect of MGRNOX index-guided general anesthesia on opioid consumption in patients undergoing laparoscopic cholecystectomy and the primary hypothesis of our study is that using the MGRNOX index to guide intraoperative pain management during general anesthesia can significantly reduce the consumption of remifentanil during the surgery.

Pain management is a critical component of perioperative anesthesia. Traditionally, anesthesiologists adjust analgesic dosages based on intraoperative heart rate or blood pressure, relying heavily on personal clinical experience. This approach often leads to over- or under-administration of analgesics. Currently, opioids remain the primary analgesics used in general anesthesia. Excessive opioid doses can result in postoperative hyperalgesia, delayed recovery, respiratory and circulatory depression, and increased hepatic/renal burden. Conversely, insufficient opioid doses may lead to inadequate analgesia, intraoperative hemodynamic instability, postoperative pain, and agitation.

In recent years, various nociception monitoring devices (e.g., SPI, ANI, qNOX) have been developed to quantify intraoperative nociception, assisting anesthesiologists in optimizing analgesic administration to achieve precision and balanced anesthesia. Studies suggest that nociception-guided analgesia during general anesthesia surgery reduces opioid consumption, alleviates postoperative pain, and improves hemodynamic stability compared to traditional standardized management. However, due to the limitations of existing indices, no specific parameter has yet been established as a gold standard for objectively reflecting intraoperative nociception levels.

The MGRNOX index, a China-developed metric based on central nervous system monitoring, derives from processed and quantified electroencephalographic (EEG) signals under general anesthesia to reflect a patient's analgesic state. As clinical evidence for MGRNOX remains limited and its impact on intraoperative opioid usage remains unvalidated, the investigators designed this randomized controlled trial to investigate whether MGRNOX-guided general anesthesia reduces opioid consumption during laparoscopic cholecystectomies. Our primary hypothesis is that intraoperative MGRNOX-guided analgesia will significantly decrease remifentanil requirements.

Inclusion Criteria:

• Age ≥18 years old and < 65 years old；
• American Society of Anesthesiologists (ASA) class I-II；
• Scheduled to undergo elective laparoscopic cholecystectomy undergeneral anesthesia （without epidural anesthesia, local blocks, or infiltration）

Exclusion Criteria:

• Pregnancy or lactation period；
• BMI ≥35 kg/m² or <18.5 kg/m²；
• Anticipated difficult airway；
• Previous diagnosis of hypertension；
• History of drug or alcohol abuse within the past 6 months；
• Preoperative acute or chronic pain history (routine preoperative use of opioid or non-opioid analgesics), peripheral or central nervous system-related disorders；
• Definitively diagnosed psychiatric disorders or other neuropsychiatric conditions severely affecting cognitive judgment, history of psychotropic medication use；
• Allergy or intolerance to anesthetic agents；
• Baseline mean arterial pressure (MAP) <60 mmHg or >120 mmHg; baseline heart rate (HR) <45 bpm or >90 bpm (Baseline values defined as first measurement taken in the ward after admission)；
• History of severe underlying diseases (untreated or ongoing peripheral/central cardiovascular diseases, severe hepatic disorders with elevated bilirubin/INR or hypoalbuminemia, severe renal diseases with elevated creatinine, severe pulmonary diseases potentially causing acute respiratory failure or persistent dyspnea)；
• Implanted pacemaker, chronic arrhythmia, preoperative use of prescribed anticholinergics, α2-adrenergic agonists, beta-1 adrenergic antagonists, or antiarrhythmic medications.