Rationale and design of the SMILe (Spinal Morphine or Intravenous Lidocaine) study: protocol for a multicentre randomised clinical trial in southern Sweden on whether spinal morphine improves postoperative recovery compared to intravenous lidocaine in patients undergoing robot-assisted upper urinary tract surgery.

introductionRobot-assisted laparoscopic surgical procedures are commonly perceived to result in fast recovery; however, the postoperative course can be challenging for many patients. We have previously found severe pain and a significant decrease in the patient-reported outcome measure Quality-of-Recovery 15 (QoR-15) in a cohort of patients undergoing robot-assisted upper urinary tract surgery. In similar settings, intrathecal analgesia is sometimes used to improve recovery; however, its benefits have not been established. Therefore, this study aims to examine the effects of intrathecal analgesia in this setting compared with an active comparator intravenous lidocaine. METHODS AND ANALYSIS: In this randomised, assessor-blinded multicentre trial, 220 patients scheduled for robot-assisted upper urinary tract surgery under general anaesthesia are recruited after obtaining informed consent. They are randomised to receive either intrathecal analgesia or an intraoperative infusion with lidocaine. The primary study outcome is the decrease in QoR-15 from baseline to postoperative day 1. Other outcomes of interest include postoperative pain, length of stay and postoperative complications. Differences in intraoperative haemodynamics and postoperative inflammatory parameters will also be analysed. ETHICS AND DISSEMINATION: This study has been approved by the Swedish Medical Products Agency (5.1.1-2023-69740 and 5.1.2-2025-030145). The results of this study will be presented at national and international meetings and submitted for publication in peer-reviewed international medical journals. TRIAL REGISTRATION NUMBER: NCT06349668.