Gastrointestinal tumor is one of the highest incidence of malignant tumors in our country, with the incidence increasing year by year. Laparoscopic gastrointestinal surgery ,due to having less bleeding ,small trauma ,Rapid recovery ,has become the main means for the treatment of gastrointestinal surgery. Under general anesthesia, mechanical ventilation can lead to repeated mechanical dilation of alveoli, which can lead to mechanical injury of alveolar epithelium, reduce lung compliance, affect lung function, and increase postoperative complications and hospital stay of patients. Glycopyrrolate acts selectively on M1 and M3 receptors, and is 3-5 times more selective to M3 and M1 receptors than M2 receptors. Therefore, as preoperative medication for elderly patients, it has less effect on the cardiovascular system and can stabilize the heart rate,compared with atropine.However, its influence on the respiratory system in the field of anesthesia is only limited to the study of inhibiting glandular secretion at present, and there are no clear reports on the study of respiratory mechanics. The objective of this study was to evaluate the effect of glycopyrrolate on oxygenation index in elderly patients undergoing radical surgery for gastrointestinal malignant tumor.

Inclusion Criteria:

1. aged 65 yrs or elder;
2. gender unlimited;
3. American Society of Anesthesiologists (ASA) class I to III;
4. an expected surgical duration of at least 2 hrs.

Exclusion Criteria:

1. refusal to participate;
2. known allergy to glycopyrrolate;
3. severe hepatic or renal insufficiency;
4. myasthenia gravis;
5. angle-closure glaucoma;
6. tachycardia detected on the preoperative electrocardiogram (ECG);
7. contraindications to epidural anesthesia;
8. a history of mechanical ventilation within the past six months;
9. severe respiratory disease or restricted thoracic mobility such as thoracic deformity.