Gastric regurgitation increases the risk of pulmonary aspiration in surgical patients receiving general anesthesia because of depression of gastro-esophageal reflux. In addition, some patients may have higher risk of aspiration as a result of reduced gastric emptying and gastroesophageal reflux, prolonged surgical time, and laparoscopic surgery. Second-generation supraglottic airway device (SAD) provides an additional channel to facilitate the drainage the gastric content to prevent from aspiration, which was routinely used in surgeries. Currently, multichannel intraluminal impedance-pH (MII-pH) monitoring, which combines multiple impedance channels to conventional pH catheters, is regarded as the most sensitive technique for detecting reflux events. Therefore, application of MII-pH monitoring on the SAD-based general anesthesia may help to detect ongoing reflux/regurgitation in the esophagus of patients during perioperative period. The hypothesis of the present study is that the occurrences of gastroesophageal regurgitation during general anesthesia may be influenced by the several factors, such as abdominal insufflation during laparoscopy, longer surgical time, Trendelenburg position, higher body weight, etc.

Investigators aim to observe the occurrences of gastroesophageal regurgitation through the continuous monitoring with the novel technique of MII-pH during the perioperative period of a variety of common surgical procedures under SAD-based general anesthesia in this pilot study. Furthermore, investigators will also determine the factors associated with the occurrence of gastroesophageal regurgitation during these various surgical procedures under general anesthesia.

Investigators include the patients who will receive scheduled surgery under SAD-based general anesthesia and aged >= 20 will be enrolled. All subjects provide basic demographic data and fill in standard symptom questionnaire for evaluation of baseline severity of gastroesophageal reflux and other associated gastrointestinal and sleep symptoms. Supraglottic airway device with i-gel will be inserted to establish airway, and the gastric content will be suctioned out through the esophageal vent of i-gel. MII-pH catheter will be inserted though the esophageal vent of i-gel to detect and characterize gastroesophageal reflux events in the perioperative period. After removal of SAD, the patients were follow the saturation, sore throat or hoarseness in the postoperative care unit, as well as the possible complications.

Investigators will not only elucidate the clinical characteristics and risk factors in patients receiving elective surgeries, but also determine the severity of gastric regurgitation during the intraoperative period.

Investigators will correlate the reflux pattern, frequency, content and proximal extent of all reflux events and symptom correlation with clinical features in the intraoperative period. The study results could help us study more in the gastric regurgitation in perioperative period.

Inclusion Criteria:

1. Patients who will receive scheduled surgery under SAD-based general anesthesia
2. Aged >= 20

Exclusion Criteria:

1. Major systemic disease, such as congestive heart failure, liver cirrhosis, end stage renal disease and malignancy.
2. Patients who have the risk of difficult ventilation or intubation.
3. pregnant women
4. prior nasal surgery or trauma
5. current use anticoagulant or antiplatelet agents
6. coagulopathy

Consecutive patients who will receive scheduled surgery under supraglottic airway device-based general anesthesia and aged >= 20 will be enrolled.

We did not plan to share our data, because it involved the patients' privacy.