A safe and effective surgical environment is important for nonintubated thoracoscopic surgery. The investigators hypothesize that mini-dose succinylcholine can induce ultra-short period of apnea, by which the ventilatory responses to open pneumothorax were abolished and may facilitate rapid and satisfying collapse of the operated lung during nonintubated thoracoscopic surgery.

Background: Nonintubated thoracoscopic surgery is the frontier of modern minimal invasive thoracic surgery. A safe and effective surgical environment is established via an iatrogenic open pneumothorax producing the operated lung fully collapsed. However, the initial respiratory response to open pneumothorax is both tachypnea and carbon dioxide rebreathing, which would jeopardize the quality of collapse of the operated lung and delay the performance of intrathoracic vagal block. Intravenous opioid is effective to attenuate ventilatory responses but herein with risk of persistent respiratory depression.

Methods: The investigators hypothesize that mini-dose succinylcholine 0.15 mg/kg can induce ultra-short period of apnea, by which the ventilatory responses to open pneumothorax were abolished and may facilitate rapid and satisfying collapse of the operated lung during nonintubated thoracoscopic surgery. In a prospective, randomized, double-blind study design, 30 patients will be allocated to receive either succinylcholine (n=15) or placebo (n=15) in the beginning of open pneumothorax. The effectiveness of succinylcholine will be measured by the surgeon's evaluation of the quality of lung collapse, while the safety will be evaluated by determination of arterial blood gases within 20 minutes of one-lung spontaneous breathing.

Expected results: Mini-dose succinylcholine can facilitate early lung collapse without jeopardizing the ventilatory function during nonintubated thoracoscopic surgery with one-lung spontaneous breathing, which may make nonintubated thoracoscopic surgery easier and safer.

Inclusion Criteria:

• Adults patients with lung tumors and elective for unilateral thoracoscopic surgery.

Exclusion Criteria:

• Over weighted, body mass index > 26 kg/m2.
• Previous thoracic surgery on the attempted operative side.
• Hypoventilation syndrome requiring positive pressure ventilatory support or oxygen at home.
• Relevant systemic disease, including heart failure, liver failure, renal failure with an American Society of Anesthesiologists (ASA) class above 3.
• Difficult airway management.
• Pregnancy.
• Contraindications for succinylcholine, including family history of suspicious malignant hyperthermia, hyperkalemia, or other neuromuscular diseases.