Postoperative pulmonary complications (PPCs) are major causes of postoperative morbidity, mortality, and prolonged hospital stay.The incidence of PPCs may be as high as 41% to 75% in high-risk patients. Bronchodilator is frequently used in high-risk patients to prevent PPCs. Penehyclidine is a new anticholinergic agent which selectively block M1 and M3, but not M2 receptors. A pilot study of the investigators showed that prophylactic penehyclidine inhalation reduced the incidence of bronchospasm and the use of aminophylline in elderly patients after long-duration surgery. The purpose of this study is to investigate whether prophylactically penehyclidine inhalation could decrease the incidence of PPCs in high-risk patients after major intrathoracic and upper intraabdominal surgery.

Postoperative pulmonary complications (PPCs) are major causes of postoperative morbidity, mortality, and prolonged hospital stay. The incidence of PPCs was found to vary from 2 to 19%, but this rate might be as high as 41 to 75% in patients after intrathoracic and intraabdominal surgery. According to Canet's model, the predicted incidence of PPCs in high-risk patients (ARISCAT risk index >= 45 points) is 42.1%. Use of effective strategies to prevent PPCs is essential for these patients.

Strategies that have been proved to be beneficial in decreasing PPCs include smoking cessation, proper management of chronic obstructive pulmonary disease before surgery, as well as use of lung-protective ventilation and goal-directed fluid therapy during surgery. Besides, bronchodilator inhalation is also helpful. Studies showed that, in high-risk patients undergoing intrathoracic surgery, airway resistance was increased due to bronchial hyperresponsiveness, which increased the risk of PPCs. Inhalation of anticholinergic bronchodilator can reduce the activity of vagus nerve and relieve high airway resistance, which may decrease the risk of bronchospasm and other PPCs.

It has been shown that M1, M3-receptor selective blockers have better effects than β2-receptor activator in dilating bronchia. Global Strategy for the Diagnosis, Management, and Prevention of Chronic Obstructive Pulmonary Disease (updated 2014) published by Global Initiative for Chronic Obstructive Lung Disease (GOLD) recommend the use of M1, M3-receptor selective blockers to relieve acute exacerbation of chronic obstructive pulmonary disease (COPD) and improve pulmonary function.

Penehyclidine hydrochloride is a new anticholinergic agent, which selectively blocks M1 and M3, but not M2 receptors. Preclinical studies found that it also has anti-inflammation effects. In a pilot study of the investigators, prophylactic inhalation of penehyclidine decreased the incidence of bronchospasm and the use of aminophylline in elderly patients after long-duration surgery. The investigators propose that prophylactic inhalation of penehyclidine might decrease the incidence of PPCs in high risk patients.

The purpose of this study is to investigate whether prophylactic penehyclidine inhalation could decrease the incidence of PPCs in high-risk patients after major intrathoracic and upper intraabdominal surgery.

Inclusion Criteria:

1. Age >50 years;
2. Scheduled to undergo upper abdominal or noncardiac thoracic surgery with expected duration ≥2 hours. For those who undergo laparoscopic or thoracoscopic surgery, the expected length of incision must be ≥5 cm;
3. Judged to be at high risk of PPCs according to the ARISCAT risk score (ARISCAT predictive score ≥45).

Exclusion Criteria:

1. American Society of Anesthesiologists (ASA) physical classification ≥IV or the expected survival duration ≤24 hours;
2. Preoperative history of symptomatic hypertrophy or glaucoma;
3. History of myocardial infarction, severe heart dysfunction (New York Heart Association functional classification ≥3) or tachyarrhythmia within one year;
4. Inhalation of β2-receptor activator, M-receptor blockers and/or glucocorticoids within one month before surgery;
5. Severe renal dysfunction (requirement of renal replacement therapy) or severe hepatic dysfunction (Child-Pugh grade C);
6. History of acute stroke within three months before surgery;
7. Refuse to participate in the study or unable to cooperate with the inhalation therapy;
8. Participation in other clinical trial during the last month or within the six half-life periods of the study drug used in the last trial.