Multimodal Opioid-Free Anesthesia in RIRS

Opioids have traditionally been the cornerstone of perioperative analgesia; however, opioid-related adverse effects such as respiratory depression, postoperative nausea and vomiting (PONV), opioid-induced hyperalgesia, sedation, and delayed recovery may negatively affect postoperative outcomes. Opioid-free anesthesia (OFA) is a multimodal anesthetic approach that aims to provide adequate analgesia while minimizing or eliminating perioperative opioid exposure.

Dexmedetomidine and ketamine are commonly used components of OFA protocols. Dexmedetomidine provides sedation and analgesia through selective alpha-2 adrenergic receptor agonism without significant respiratory depression, whereas ketamine reduces central sensitization and opioid-induced hyperalgesia through NMDA receptor antagonism. Their combined use may provide synergistic analgesic and hemodynamic effects.

Retrograde intrarenal surgery (RIRS) is a minimally invasive endourological procedure commonly performed for renal stone disease. Rapid postoperative recovery and early discharge are important goals in this patient population. The use of laryngeal mask airway (LMA) may further facilitate smoother airway management and recovery.

This prospective, randomized, single-center, assessor-blinded clinical trial will compare a dexmedetomidine-ketamine based OFA protocol with conventional fentanyl-based anesthesia in adult patients undergoing elective RIRS under LMA. Eligible participants will be randomized in a 1:1 ratio to either the opioid-free anesthesia group or the opioid-based anesthesia group.

The primary outcomes are postoperative pain scores assessed using the Numeric Rating Scale (NRS) and postoperative opioid consumption during the early recovery period. Secondary outcomes include recovery characteristics, intraoperative hemodynamic parameters, quality of LMA removal, intraoperative patient movement, postoperative nausea and vomiting, surgeon satisfaction, and perioperative adverse events.

The investigators hypothesize that the OFA protocol may reduce postoperative opioid requirements and improve recovery quality while maintaining adequate perioperative analgesia and hemodynamic stability.

Inclusion criteria

Aged 18 to 65 years ASA physical status I or II ASA III patients with controlled and stable systemic disease (e.g., well-controlled hypertension or type 2 diabetes without end-organ damage) Scheduled for elective retrograde intrarenal surgery (RIRS) under laryngeal mask airway (LMA) Ability to provide written informed consent

Exclusion criteria

BMI greater than 40 kg/m² Chronic opioid use Severe cardiovascular disease (uncontrolled arrhythmia, unstable angina, or ejection fraction below 40%) Significant respiratory disease (FEV1 below 60% predicted or oxygen-dependent COPD) Neuropsychiatric disorders Pregnancy Known allergy to any study drug Anticipated difficult airway (Mallampati III-IV, mouth opening less than 3 cm, or thyromental distance less than 6 cm) Requirement for conversion from LMA to endotracheal intubation Emergency cases Withdrawal of informed consent