Nonintubated anesthesia applied in combination with high-flow nasal oxygen (HFNO) is an alternative strategy for laryngeal microsurgery (LMS). LMS is a common procedure in otolaryngology that typically requires endotracheal tube intubation under general anesthesia. Endotracheal tube intubation causes complications; a nonintubated strategy can avoid these complications and provide a clearer surgical field of vision, enabling vocal cord inspection and disposal. Administering a muscle relaxant can also help prevent bucking during surgery but can engender apnea and hypercapnia, which may have negative effects on hemodynamics. Therefore, the investigators assessed the effectiveness of a superior laryngeal nerve block (SLNB) with intravenous general anesthesia in maintaining spontaneous breathing and improving safety during LMS with nonintubated anesthesia.

Laryngeal microsurgery (LMS) is among the most common operations in otolaryngology and typically requires general anesthesia administered through endotracheal tube intubation. Endotracheal tube intubation provides stable gas exchange, protects the airways by preventing secretions from falling into the lower respiratory tract, and enables the monitoring of parameters such as tidal volume and end-tidal CO2.

Nonintubated anesthesia applied in combination with transnasal humidified rapid-insufflation ventilatory exchange or high-flow nasal oxygen (HFNO) is another option for LMS. LMS with nonintubated anesthesia can avoid the complications caused by endotracheal tube intubation such as oral tissue trauma, tracheal trauma, and dental injury. Furthermore, LMS with nonintubated anesthesia can provide a clearer surgical field of vision that allows the vocal cords to be inspected and disposed of completely. Current practice in LMS with nonintubated anesthesia is to administer a muscle relaxant to help avoid bucking during the procedure. However, the administration of a muscle relaxant can lead to apnea and hypercapnia, which may negatively affect hemodynamics. Therefore, the investigators investigated the use of a superior laryngeal nerve block (SLNB) with intravenous general anesthesia to help the patient maintain spontaneous breathing and provide higher surgical safety during LMS with nonintubated anesthesia.

Inclusion Criteria:

• The patient who needed to undergo LMS.

Exclusion Criteria:

• Severe airway obstruction.
• Severe airway disease.
• American Society of anesthesiologists (ASA) physical state > III.
• Pregnancy or body mass index (BMI) ≥ 40 kg/m2.