The goal of this clinical trial is to evaluate whether mivacurium chloride and succinylcholine can provide effective and safe muscle relaxation in adult patients aged 18-60 years undergoing bronchoscopy who require muscle relaxants during anesthesia. The main questions it aims to answer are:

• Is the recovery of spontaneous breathing within 15 minutes after drug discontinuation with mivacurium chloride non-inferior to succinylcholine?
• How do mivacurium chloride and succinylcholine compare in terms of intraoperative hemodynamics and post-operative recovery and comfort? Researchers will compare the mivacurium chloride group and the succinylcholine group to observe if mivacurium chloride can provide similar or better recovery effects compared to succinylcholine.

Participants will:

• Receive either mivacurium chloride (0.14 mg/kg induction bolus + 0.5 mg/kg/h maintenance infusion) or succinylcholine (1 mg/kg induction bolus + 5 mg/kg/h maintenance infusion) as a muscle relaxant during bronchoscopy.
• Have their vital signs, including blood pressure, oxygen saturation, and heart rate, monitored at multiple time points during the procedure.
• Be assessed post-procedure for spontaneous breathing recovery, consciousness recovery, and time to laryngeal mask airway (LMA) removal, as well as overall comfort and satisfaction.

Inclusion Criteria:

1. Patients scheduled for painless bronchoscopy who require muscle relaxants during anesthesia.
2. Aged between 18 and 60 years.
3. Classified as Grade I-III according to the American Society of Anesthesiologists (ASA) Physical Status Classification.
4. Patients voluntarily participate and sign an informed consent form.

Exclusion Criteria:

1. Patients with known allergies to any of the drugs involved in the study.
2. Patients with severe organic diseases of the brain, heart, lungs, liver, kidneys, or other major organs.
3. Patients with intracranial hypertension, asthma, cataracts, glaucoma, or other eye diseases.
4. Patients with myasthenia gravis, myasthenic syndrome, severe reduction or deficiency of cholinesterase, upper motor neuron injury, or upper motor neuron diseases that may cause abnormal responses to muscle relaxants.
5. Patients who have used medications affecting neuromuscular transmission function before the procedure.
6. Pregnant or breastfeeding patients.
7. Patients who have experienced extensive burns, acid-base imbalance, or electrolyte disturbances within the past six months.
8. Patients known or suspected to be homozygous for the atypical gene for plasma cholinesterase.