Intraoperative methadone or fentanyl will be administered to patients submitted to kidney transplant surgery. Postoperative pain, analgesic consumption and side effects will be evaluated

Despite recent developments in postoperative pain control, many patients still experience moderate or severe pain after surgery. It is estimated that severe postoperative pain occurs in 20 to 40% of surgical procedures. With the development of kidney transplant services, a better study of the intraoperative analgesia used in this procedure and its impact on the postoperative is necessary. The management of postoperative pain in renal transplant recipients is essential to improve the quality of postoperative care, and may even impact the prognosis of the renal graft. One of the strategies to improve pain control in the perioperative period is the intraoperative use of intravenous methadone, given its pharmacokinetic profile. Methadone is an opioid agonist of µ receptors, it is also a Glutamate antagonist by blocking the N-methyl-D-aspartate (NMDA) receptor, and inhibits the reuptake of serotonin and norepinephrine. When administered in doses of 20 to 30mg, the analgesia generated by methadone can last from 24 to 36 hours. There is also evidence that the use of methadone in doses of 0.2 to 0.3 mg / kg is not associated with a higher incidence of side effects when compared to other opioids with short or intermediate duration of action, such as fentanyl, sufentanil and morphine. The aim of this study is to evaluate the effectiveness of using intraoperative methadone to reduce postoperative pain in patients undergoing kidney transplant surgery (recipients). Patients will be submitted to standardized general anesthesia, and the opioid used in anesthetic induction will be methadone or fentanyl with additional boluses if necessary. After extubation, Fentanyl will be installed in an intravenous analgesia pump controlled by the patient. Differences between groups regarding opioid consumption, pain scores, side effects and patient satisfaction will be assessed

Inclusion Criteria:

• Patients over 18 years of age
• With indication for kidney transplant surgery
• Who sign the informed consent form

Exclusion Criteria:

• Patients who refuse to participate in the study
• Known allergy to any drug used in this protocol
• Presence of stage III or IV congestive heart failure
• Increase in QT interval on electrocardiogram (QT> 500 msec)
• Preemptive kidney transplantation (defined by transplantation in a patient who has not yet started kidney replacement therapy).