Aim: In this study, we primarily aimed to determine the effect of anterior Quadratus Lumborum Block (QLB) on intraoperative and postoperative opioid consumption in patients undergoing percutaneous nephrolithotomy (PCNL) surgery under general anesthesia. Secondarily, we aimed to evaluate opioid-related complications and investigate the impact of anterior QLB on the quality of postoperative recovery using the QoR-15 (Quality of Recovery-15) questionnaire.

Materials and Methods: The study included 60 patients aged 18-75, with ASA physical status I-III, who were scheduled for elective PCNL. Patients were randomly assigned to either the Control Group (n=30) or the Anterior QLB Group (n=30). Following dropouts during follow-up, a total of 54 patients (27 in each group) were analyzed. Preoperative block was performed in the Anterior QLB group. In both groups, following anesthesia induction, anesthesia maintenance was provided with sevoflurane to maintain a BIS value of 40-60, and the remifentanil dosage was adjusted to keep the ANI between 50-70. Operation time, surgical duration, extubation time, intraoperative hemodynamic data, ANI values, and the amount of intraoperative remifentanil consumed were recorded. Postoperative recovery unit pain scores, incidence of nausea and vomiting, and additional analgesic requirements were documented. Pain scores at the 1st, 2nd, 6th, 12th, and 24th postoperative hours, postoperative complications (nausea, vomiting, etc.), opioid consumption, and the results of the QoR-15 questionnaire at the 24th hour were recorded.

Results: Intraoperative remifentanil consumption, both in terms of total dose and weight-adjusted infusion rate, was significantly lower in the Anterior QLB group (p<0.001). Pain scores were significantly lower in the Anterior QLB group both in the recovery unit and at all postoperative time points (p<0.05). Postoperative cumulative tramadol consumption was also lower in the Anterior QLB group across all time intervals (p<0.05). No significant difference was found between the two groups regarding the incidence of postoperative nausea and vomiting. Furthermore, no significant difference was observed in the QoR-15 questionnaire scores evaluated at the 24th postoperative hour.

Conclusion: Anterior QLB is an effective analgesic method in percutaneous nephrolithotomy surgery, reducing perioperative opioid consumption and postoperative pain scores. It is concluded that anterior QLB is effective as a significant component of the multimodal analgesia strategy by preventing potential side effects associated with opioid consumption.

Inclusion Criteria:

• Age between 18 and 75 years.
• American Society of Anesthesiologists (ASA) physical status I-III.
• Patients undergoing percutaneous nephrolithotomy (PCNL) under general anesthesia

Exclusion Criteria:

• Known allergy to local anesthetics.
• Coagulopathy or bleeding disorders.
• Infection at the site of intervention.
• Neurological or neuromuscular diseases.
• Psychiatric disorders.
• Chronic pain syndromes.
• Chronic analgesic or opioid use.
• History of opioid abuse.
• Contraindications to regional anesthesia.
• Cardiac dysrhythmia that could interfere with Analgesia Nociception Index (ANI) monitoring.
• Patients requiring vasoactive or chronotropic drugs (e.g., atropine, ephedrine, nitroglycerin, or noradrenaline) to maintain hemodynamic stability during surgery.
• Refusal to participate in the study.