Tizanidine Premedication Versus Placebo for Laryngeal Mask Airway Insertion and Recovery in Adults Undergoing Ambulatory Surgery

This study will evaluate whether a single oral dose of tizanidine 4 mg given before surgery improves laryngeal mask airway (LMA) insertion conditions and postoperative recovery in adults undergoing elective ambulatory surgery under sevoflurane-based general anesthesia. Eligible adults aged 18 to 65 years with American Society of Anesthesiologists (ASA) physical status I or II will be randomly assigned to receive either oral tizanidine 4 mg or a matching placebo 60 to 90 minutes before anesthesia induction. Participants and the clinical and outcome-assessment teams will be blinded to treatment allocation. The primary outcome is the proportion of participants with excellent LMA insertion conditions at the first insertion attempt, assessed using a predefined composite score. Secondary outcomes include anesthetic and opioid requirements, hemodynamic changes, emergence and recovery times, postoperative pain, quality of recovery, and adverse effects. The study aims to determine whether tizanidine premedication improves airway insertion conditions and recovery outcomes without unacceptable adverse effects.

Inclusion Criteria * Age 18-65 years. * ASA physical status I-II. * Scheduled for elective ambulatory surgery (e.g., minor gynaecological, urological, general, or orthopaedic procedures) under general anesthesia using a standardized second-generation LMA (e.g., LMA Supreme or i-gel - one device type fixed for the entire trial). * Expected surgical duration 30-120 minutes. * Ability to understand the study and provide written informed consent. Exclusion Criteria * ASA physical status III or higher. * Predicted difficult airway (Mallampati score III-IV, inter-incisor gap \35 kg/m² (contraindication to supraglottic airway). * Known or suspected gastro-oesophageal reflux disease, hiatal hernia, or other conditions increasing aspiration risk (contraindication to LMA). * Known allergy or contraindication to tizanidine, alpha-2 adrenergic agonists, propofol, sevoflurane, or fentanyl. * Significant cardiovascular disease: symptomatic arrhythmias, uncontrolled hypertension (SBP \>160 mmHg despite treatment), second/third-degree heart block, or severe valvular disease. * Baseline bradycardia (resting HR \10 cigarettes/day) - to be recorded as a covariate if not excluded, but exclusion of heavy smokers minimizes airway reactivity confounding. * Inability or refusal to provide informed consent.