In one-lung ventilation surgery, compared with dexmedetomidine combined with propofol, dexmedetomidine combined with desflurane may be beneficial to accelerate patients' recovery and reduce postoperative pulmonary complications and does not increase the incidences of delirium and postoperative nausea and vomiting.

With the increase in the prevalence of lung cancer in recent years, the number of patients undergoing lobectomy has also increased. When performing lobectomy, inserting a double-lumen endotracheal tube or bronchial occlusive device and then ventilating the healthy lung is necessary. The affected lung is not ventilated; that is one-lung ventilation, which can fully expose the vision of the affected lung, provide space for surgical operation, and simultaneously avoid the pollution of the healthy lung. The emergence of one-lung ventilation has extensively promoted the development of thoracic surgery. However, during one-lung ventilation, the affected lung is not ventilated, and the blood flow of the affected lung is not oxygenated, which leads to increased intrapulmonary shunt and hypoxemia. Repeated and excessive inflation of the healthy lung may release many inflammatory factors, trigger local or systemic inflammatory reactions, and increase postoperative pulmonary complications. Therefore, it is an essential goal of anesthesia management to quickly wake up and resume spontaneous breathing to reduce mechanical ventilation time.

Propofol-based intravenous anesthesia and inhalation anesthesia with sevoflurane, isoflurane, or desflurane are clinics' most commonly used general anesthesia methods. It is found that inhalation anesthesia with desflurane is superior to propofol-based intravenous anesthesia in the aspects of eye-opening time, spontaneous breathing recovery time, and extubation time in outpatient surgery, lung volume reduction surgery, lung cancer surgery, and endoscopic lumbar disc surgery. In addition, several meta-analyses found that inhalation anesthesia has an anti-inflammatory effect compared with propofol-based anesthesia, which can reduce alveolar inflammatory reaction and postoperative pulmonary complications in patients with one-lung ventilation. Kawanishi et al. found that desflurane inhalation anesthesia can promote the collapse of the affected lung, shorten the operation time, and reduce the occurrence of atelectasis compared with propofol-based intravenous anesthesia. These studies show that inhalation anesthesia with desflurane is superior to propofol-based intravenous anesthesia in one-lung ventilation surgery.

However, inhalation anesthesia is not perfect, and studies have also found that inhalation anesthesia increases the incidences of restlessness during awakening and postoperative nausea and vomiting. One study found that the incidences of delirium, nausea and vomiting in the desflurane anesthesia group were 50% and 37.5% respectively, while that in the propofol-based intravenous anesthesia group was 10% and 17.5% respectively in lung cancer surgery. Therefore, it is necessary to explore an anesthesia management method that will not affect the advantages of inhalation anesthesia but also reduce the disadvantages of inhalation anesthesia.

Dexmedetomidine is a highly selective α2- adrenergic receptor agonist. Its primary function is sedation, often used as an anesthetic adjuvant. Studies have found that dexmedetomidine can significantly reduce the incidences of delirium during recovery and postoperative nausea and vomiting. In patients undergoing nasal surgery, dexmedetomidine can reduce the incidence of delirium in patients receiving desflurane anesthesia from 52.8% to 5.6%, even lower than the incidence of delirium (10%) in patients receiving propofol in lung cancer surgery. In patients undergoing laparoscopic hysterectomy, the use of dexmedetomidine can reduce the incidence of nausea and vomiting after desflurane anesthesia from 32% to 13%, even lower than that after propofol anesthesia in lung cancer surgery (17.5%). In addition, dexmedetomidine can reduce inflammatory reactions, improve oxidative stress and respiratory mechanics, reduce intrapulmonary shunt, improve oxygenation, and reduce postoperative pulmonary complications in one-lung ventilation surgery. Although dexmedetomidine has a sedative effect, this sedative effect can be awakened easily. Moreover, a meta-analysis found that dexmedetomidine did not prolong the stay time in the anesthesia recovery room but only prolonged extubation time statistically, and it had no clinical significance. In a word, a large number of meta-analyses found that dexmedetomidine can not only reduce the incidence of various adverse events after operation but also has no noticeable effect on patients' recovery.

Therefore, the investigators speculate that compared with dexmedetomidine combined with propofol, dexmedetomidine combined with desflurane is beneficial to accelerate patients' recovery and reduce postoperative pulmonary complications and does not increase the incidences of delirium and postoperative nausea and vomiting.

Inclusion Criteria:

1. Patients undergoing elective thoracoscopic unilateral lobectomy.
2. General anesthesia is required and the expected duration of one-lung ventilation is ≥ 1h.
3. American Association of Anesthesiologists (ASA) physical condition classification I-III.
4. Patients over 18 years old.
5. Voluntary participation and ability to understand and sign the informed consent.

Exclusion Criteria:

1. Obese patients (BMI>28 kg/m2).
2. patients with grade 3 hypertension (systolic blood pressure ≥180 mmHg and/or diastolic blood pressure ≥110 mmHg).
3. Acute coronary syndrome, sinus bradycardia (heart rate < 45 beats/min), II or III degree atrioventricular block, NYHA heart function classification III or IV.
4. Patients with severe history of chronic obstructive pulmonary disease (GOLD grade III or IV of pulmonary function of chronic obstructive pulmonary disease), severe or uncontrolled bronchial asthma, pulmonary infection, bronchiectasis and thoracic deformity.
5. Pulmonary artery pressure ≥60 mmHg.
6. Patients with Child grade B or C of liver function.
7. Patients with chronic kidney disease in stage 4 or 5.
8. Patients with hyperthyroidism and pheochromocytoma.
9. Patients who are expected to need mechanical ventilation after operation.
10. People with hearing, intelligence, communication and cognitive impairment.
11. For any reason, it is impossible to cooperate with the study or the researcher thinks that it is not suitable to be included in this experiment.
12. patients who are expected to be transferred to ICU after operation.

Individual participant data (IPD) will be available with the responding author when required.

The data will become available when publish and keep it for 5 years.

Researchers who provide a methodologically sound proposal.