This study aims to compare the analgesic effectiveness of the preoperatively administered Anterior Quadratus Lumborum Block (Anterior QLB) and the Transversalis Fascia Plane Block (TFP block) in children undergoing lower abdominal urogenital surgery. The study will include children aged 6 months to 12 years, with randomization performed using the sealed opaque envelope method, and outcome assessment conducted in a double-blinded manner. All patients will receive a standardized anesthesia protocol, and the regional blocks will be performed under ultrasound (US)-guided techniques.

Perioperative evaluations will include pain levels, hemodynamic responses, additional analgesic requirements, block performance time, technical success rate, and family satisfaction. Postoperative pain will be monitored using the Face, Legs, Activity, Cry, Consolability (FLACC) scale, and analgesics will be administered when necessary. By comparing these two commonly used regional anesthesia techniques, this study aims to contribute to improved perioperative pain management strategies in the pediatric population.

Regional anesthesia techniques have become increasingly preferred in pediatric anesthesia due to their ability to enhance multimodal analgesia, reduce opioid use and associated side effects, and potentially prevent the development of chronic pain (1). With the widespread adoption of ultrasonography (USG), peripheral nerve blocks have gained popularity as safer alternatives to central neuraxial blocks, which carry a higher complication risk. Truncal blocks have become particularly important in abdominal surgeries. Various quadratus lumborum block (QLB) approaches have demonstrated the ability to provide extensive sensory blockade (T4-L2 dermatomes) in cadaveric and clinical studies. However, because the number of randomized controlled trials in this area remains limited, further research is needed to better establish the efficacy of QLB (2).

The anterior quadratus lumborum block (Anterior QLB) provides effective analgesia for procedures such as inguinal hernia repair and orchiopexy, likely due to its potential spread toward the paravertebral space. The transversalis fascia plane (TFP) block provides analgesia by anesthetizing the ilioinguinal and iliohypogastric nerves as they travel along the ventral surface of the quadratus lumborum muscle and course between the transversalis fascia and the transversus abdominis muscle. These nerves originate from the anterior ramus of the L1 spinal nerve, with contributions from T12.

As a primary endpoint, we predict that the TFPB group will have lower FLACC scores in the intraoperative and early and late postoperative periods compared to the anterior QLB group, and consequently, lower opioid and non-opioid drug consumption. As a secondary endpoint, we hypothesize that patient and family satisfaction levels will be higher in the TFPB group during the first 24 hours postoperatively.

Methods:

Children aged 6 months to 12 years scheduled for inguinal hernia repair or orchiopexy will be enrolled. Exclusion criteria include allergy to local anesthetics, infection at the injection site, coagulopathy or other contraindications to regional anesthesia, inability to obtain informed consent, planned laparoscopic orchiopexy, American Society of Anesthesiologists (ASA) physical status class IV, and anticipated postoperative intensive care requirements.

Randomization will be performed using a sealed opaque envelope method, and outcome assessment will be double-blinded. Following premedication, all participants will undergo standard monitoring, including electrocardiography (ECG), peripheral oxygen saturation (SpO₂), and non-invasive blood pressure (NIBP) measurement. Anesthesia induction will be performed with thiopental, fentanyl, and rocuronium, followed by intubation; maintenance anesthesia will be achieved with sevoflurane.

Participants will be allocated into two groups:

Group 1: Anterior Quadratus Lumborum Block (Anterior QLB)

Group 2: Transversalis Fascia Plane Block (TFP block)

All blocks will be performed under sterile conditions using a linear ultrasound transducer and an in-plane technique with appropriately sized (18-22 gauge) intravenous cannulas. All patients will receive 0.4 mL/kg of 0.25% bupivacaine.

Perioperative monitoring will include recording the block-to-incision duration and heart rate (HR) and blood pressure (BP) measurements at baseline and at 5, 10, 20, 30, 45, and 60 minutes after incision. If additional analgesia is required, remifentanil infusion will begin at 0.1 mcg/kg/min and be titrated in response to hemodynamic changes.

Postoperatively, patients will be monitored for 2 hours in the recovery unit and then transferred to the pediatric surgery ward. Pain will be assessed using the Face, Legs, Activity, Cry, Consolability (FLACC) scale, and patients with a FLACC score of ≥4 will receive acetaminophen and/or tramadol. Families will receive information regarding postoperative pain management, and structured telephone follow-up will be conducted at 16 and 24 hours to evaluate family satisfaction, which will be recorded on a 3-point scale (1 = not satisfied, 2 = partially satisfied, 3 = very satisfied).

This study aims to compare the analgesic efficacy of two regional anesthesia techniques widely used in pediatric urogenital surgery and to contribute to the development of safer and more effective perioperative pain management strategies in children.

Inclusion Criteria:

• Age 6 months to 12 years
• Scheduled for lower abdominal urogenital surgery (e.g., inguinal hernia repair, undescended testis surgery)
• ASA physical status I-III
• Parental/guardian informed consent obtained

Exclusion Criteria:

• Allergy to local anesthetics
• Infection at the injection site
• Coagulopathy or other contraindications to regional anesthesia
• Laparoscopic orchiopexy scheduled
• ASA physical status IV
• Inability to obtain consent from parent/guardian
• Expected need for postoperative intensive care

The anesthesiologist who evaluated the inclusion and exclusion criteria, monitored clinical pain scores and analgesic consumption during the intraoperative and postoperative periods, and performed data analysis, as well as the patients included in the study, were blinded. The anesthesiologist who knew the groups and performed the block application could not be blinded due to the study design. Postoperative ward monitoring was recorded in the late period, and pain levels were assessed every 4 hours by blinded ward nurses. During this period, patients with a FLACC score ≥4 were given 10 mg/kg paracetamol as a rescue analgesic. Patients were evaluated at 16 and 24 hours by the blinded investigator who performed clinical monitoring; pain scores and analgesic consumption data were obtained from nurse observation forms.