Tramadol / Magnesium in Ropivacaine Solution in UG-bilateral TAP Block and Analgesia in Robotic Radical Prostatectomy

Tramadol and magnesium have already been researched in recent decades for their different roles in pain control. This clinical study will compare and re-evaluate their effect on the duration and quality of analgesia provided by a regional anesthesia technique. Participants will be men aged 40 to 80 years with prostate cancer who are scheduled for robot-assisted radical prostatectomy. Initially, all patients will receive general anesthesia and will then be randomly divided into three groups of 35 patients each to undergo bilateral transverse abdominal plane (TAP) block under aseptic conditions. This involves insertion of a needle into the plane between the internal oblique and transverse abdominal muscles under ultrasound guidance in order to inject the local anesthetic solution, as the responsible nerves run through the muscles of the abdominal wall. Specifically, 35 patients will receive only local anesthetic (ropivacaine), 35 will receive ropivacaine plus tramadol, and 35 will receive ropivacaine plus magnesium. Neither the researchers nor the participants will be aware of the composition of the solution administered (double-blind randomized controlled trial). The two co-primary endpoints are: (1) intraoperative fentanyl consumption, guided by the Nociception Level (NOL) index, and (2) postoperative pain intensity assessed by the Numeric Rating Scale (NRS, 0-10) at 8 time points within the first 24 hours (at 5, 15, 30, and 60 minutes in the Post-Anesthesia Care Unit and at 2, 4, 8, and 24 hours on the ward, both at rest and on coughing), analysed by global repeated measures ANOVA. Secondary endpoints include total rescue tramadol consumption and time to first rescue dose in the first 24 postoperative hours, sedation level assessed by the Ramsay Sedation Scale and peripheral oxygen saturation (SpO₂) as safety parameters, and the incidence of postoperative nausea and vomiting (PONV). In addition, researchers will contact participants at 1, 3, and 6 months postoperatively to assess chronic pain. The sample size was determined by a pre-planned interim analysis (n=30): the fentanyl endpoint requires n=35 per group (N=105 total) to achieve 80% power (Cohen's f=0.308, α=0.05). The study will be conducted at Aretaieio University Hospital in Athens under the supervision of Anesthesiology Professors. There are no additional risks or costs beyond those normally associated with radical prostatectomy, as TAP block has already been adopted as an analgesic method at Aretaieio Hospital.