This study compares two pain control techniques in patients undergoing laparoscopic kidney donation surgery: transversus abdominis plane (TAP) block versus wound infiltration with local anesthetic.

Postoperative pain can impair breathing by causing patients to take shallow breaths to avoid discomfort. This study will evaluate which technique better preserves lung function, specifically peak expiratory flow (PEF), after surgery.

Eighty patients will be randomly assigned to receive either a TAP block (injection of local anesthetic into the abdominal wall muscles before surgery) or wound infiltration (injection of local anesthetic at the incision sites at the end of surgery). Both patients and the staff measuring outcomes will be blinded to group assignment.

The primary outcome is the percentage change in PEF from before surgery to discharge from the recovery room. Secondary outcomes include pain scores, opioid use, breathing complications, and length of hospital stay.

Laparoscopic living donor nephrectomy (LLDN) is the gold-standard approach for kidney donation, offering reduced pain, shorter hospital stays, and faster recovery compared to open surgery. However, postoperative pain remains a concern, particularly because acute pain leads to protective "splinting" breathing patterns - shallow, rapid breaths that limit abdominal wall movement. This restricted breathing reduces thoracic expansion, inhibits deep inspiration, and impairs effective coughing, increasing the risk of pulmonary complications.

Among regional analgesic techniques, TAP block and wound infiltration have emerged as promising options for LLDN due to their simplicity and effectiveness. TAP block involves ultrasound-guided injection of local anesthetic between the internal oblique and transversus abdominis muscles, providing analgesia to the anterolateral abdominal wall. Wound infiltration directly targets the surgical incision sites. While both techniques reduce postoperative pain and opioid consumption, their comparative effectiveness in preserving pulmonary function remains unclear.

This double-blind randomized controlled trial will compare the effects of TAP block versus wound infiltration on peak expiratory flow (PEF) preservation following LLDN. All patients will receive standardized general anesthesia and multimodal analgesia.

Inclusion Criteria:

• Patients who are scheduled to undergo elective LLDN.
• Age above 18 years.
• Body Mass Index (BMI) above 20 and below 40 kg m-2.
• Eligible to sign informed consent.

Exclusion Criteria:

• Open or hand-assisted surgery.
• Known cardiac or pulmonary disease.
• Preoperative chronic pain (i.e., fibromyalgia, chronic neuropathic pain).
• Contraindication for regional analgesia (i.e., known allergy to LA, skin lesions in the injection site).
• Known allergy to one or more of the components of multimodal analgesia (i.e., opioids, paracetamol, tramadol, dipyrone).
• Preexisting severe pulmonary disease (i.e., an obstructive lung disease with a forced expiratory volume in the first second [FEV1] below 49%, restrictive lung disease with a forced vital capacity [FVC] below 49%, pulmonary hypertension).

Discontinuing criteria:

Participants will be excluded from the analysis if they:

• Experience intraoperative bleeding requiring transfusion of more than three units of blood products.
• Experience hemodynamic instability requiring postoperative vasopressor or inotropic support.
• Require conversion to open surgery.
• Require mechanical ventilation after being transferred from the OR to the PACU.

Operating room staff (anesthesiologists and surgeons) are unblinded due to the nature of the interventions. Patients, the physician measuring peak expiratory flow, PACU staff, and transplantation surgical ward nursing staff are blinded to group assignment.