The aim of this clinical trial is to evaluate the effectiveness of transnasal transmucosal sphenopalatine ganglion block in reducing post-tonsillectomy pain. The study also investigates its impact on rescue analgesic requirements and postoperative recovery by comparing 5% lidocaine with placebo.

Participants will receive a transnasal transmucosal sphenopalatine ganglion block with either 5% lidocaine or placebo (saline). Postoperative pain levels and opioid consumption will be monitored during the first 24 hours after surgery. In addition, length of hospital stay, the occurrence of primary and secondary post-tonsillectomy hemorrhage up to 14 days, unplanned hospital readmissions after discharge, and patient satisfaction on postoperative day 14 will be assessed.

The primary objective of this study is to compare the effects of preemptive transnasal transmucosal sphenopalatine ganglion block performed with either 0.9% saline (placebo) or 5% lidocaine (active drug), in addition to standard multimodal analgesia, on postoperative pain and recovery in patients aged 12 years and older undergoing tonsillectomy.

All patients will undergo routine monitoring, including noninvasive blood pressure, electrocardiography (ECG), peripheral oxygen saturation (SpO₂), body temperature, end-tidal carbon dioxide (ETCO₂), and bispectral index (BIS), followed by induction of general anesthesia.

For induction of general anesthesia, intravenous lidocaine 1 mg/kg, fentanyl 1 µg/kg, and propofol 1-3 mg/kg (adjusted according to depth of anesthesia monitoring) will be administered. Neuromuscular blockade required for endotracheal intubation and surgery will be achieved with intravenous rocuronium 0.8 mg/kg. Airway security will be ensured by orotracheal intubation. Anesthesia maintenance will be provided as total intravenous anesthesia (TIVA) using a propofol and remifentanil combination, guided by BIS monitoring.

Immediately after induction of anesthesia, patients will be randomized into either the Saline Group (placebo) or the Lidocaine Group (5% lidocaine, active drug) using a computer-generated randomization program.

Before the start of surgery, a preemptive transnasal transmucosal sphenopalatine ganglion block will be performed. Patients in the placebo group will receive 0.9% isotonic saline, while patients in the lidocaine group will receive 5% lidocaine. Cotton-tipped applicators will be used for the block procedure, with one applicator inserted into each nostril. The applicators will be advanced parallel to the nasal floor from the middle turbinate until resistance is encountered. Contact of the applicator with the posterior wall of the nasopharynx will ensure transmucosal proximity to the sphenopalatine ganglion. The assigned solutions will be applied via the applicators according to group allocation, aiming for transmucosal absorption and therapeutic effect on the target ganglion.

The applicators will be shortened as necessary to avoid interference with the surgical field and will be left in place throughout the surgery. Before emergence from anesthesia, the same solution will be reapplied through the applicators. Patients will be awakened approximately 10 minutes after the second application, prior to extubation. The total volume of solution administered per patient will be 3 mL: 2 mL (1 mL per applicator) before surgery and 1 mL (0.5 mL per applicator) after surgery.

As part of standard multimodal analgesia, all patients will receive intravenous paracetamol 1 g, ibuprofen 400 mg, and dexamethasone 8 mg. For postoperative nausea and vomiting prophylaxis, ondansetron 4 mg IV will be administered before the end of surgery. Extubation will be performed after neuromuscular recovery is confirmed with a train-of-four (TOF) ratio ≥ 0.9, using sugammadex as needed.

Following transfer to the post-anesthesia care unit (PACU), all patients will receive intravenous fentanyl via patient-controlled analgesia (PCA) and will continue to be monitored using standardized case report forms. Fentanyl PCA will be prepared for all patients with a concentration of 10 µg/mL, a bolus dose of 0.2 µg/kg, a lockout interval of 12 minutes, and a maximum dose of 5 µg/kg over a 4-hour period.

In the preoperative period, demographic data of all patients will be recorded along with American Society of Anesthesiologists (ASA) physical status, Mallampati score, and Brodsky Tonsil Hypertrophy Scale. The presence of preoperative dysphagia, aspiration risk, and throat pain will also be documented.

During the intraoperative period, whether endotracheal intubation is achieved on the first attempt and the occurrence of any complications during intubation or extubation (including the type of complication, if present) will be recorded. In addition, heart rate (HR), arterial blood pressure values (systolic, diastolic, and mean arterial pressure [MAP]), peripheral oxygen saturation (SpO₂), end-tidal carbon dioxide (ETCO₂), and bispectral index (BIS) values will be recorded before anesthesia induction, after induction (corresponding to the pre-block period), and every 5 minutes intraoperatively.

Postoperative follow-up will be performed in the post-anesthesia care unit (PACU), at postoperative hours 1, 2, 4, 8, 16, and 24, and on postoperative day 14. In the PACU, patients will be evaluated by an anesthesiologist for pain (assessed using the Numeric Rating Scale [NRS]), postoperative nausea and vomiting, and potential airway-related complications, including aspiration, hoarseness, laryngospasm, dyspnea, stridor, and oxygen requirement. Patients with a Modified Aldrete Score ≥ 9 will be discharged from the PACU.

At postoperative hours 1, 2, 4, 8, 16, and 24, NRS pain scores will be recorded. In addition, the presence of nausea and vomiting, the need for additional (rescue) analgesia, and any airway-related complications will be documented. The time to first oral intake of fluids and solid foods, as well as any associated pain during oral intake, will also be monitored.

Finally, length of hospital stay, the occurrence of primary and secondary post-tonsillectomy hemorrhage up to postoperative day 14, any unplanned hospital readmissions after discharge, and patient satisfaction on postoperative day 14 will be assessed.

Inclusion Criteria:

• Patients aged ≥ 12 years
• Patients weighing ≥ 50 kg
• Patients without coagulation disorders
• ASA physical status I-II patients scheduled for tonsillectomy
• Patients who are fully oriented and able to cooperate

Exclusion Criteria:

• Lack of informed consent
• Patients aged < 12 years
• Patients weighing < 50 kg
• Body mass index (BMI) > 30 kg/m²
• History of allergy to local anesthetics
• History of facial trauma or infection
• Presence of coagulation disorders
• Patients who are disoriented and/or unable to cooperate
• Patients with comorbidities requiring opioid use
• History of neuropathic pain
• Patients with chronic pain syndrome

Individual participant data will not be shared because the study was not designed with a data-sharing plan and to ensure participant confidentiality.