Effect of Ondansetron on Patient Tolerance, Efficacy and Endoscopist Workload in Unsedated Endoscopy for Upper Gastrointestinal Bleeding

The goal of this clinical trial is to evaluate whether intravenous ondansetron can improve patient tolerance and reduce discomfort during unsedated emergency esophagogastroduodenoscopy (EGD). The main questions it aims to answer are: * Does pre-procedural administration of ondansetron improve patient cooperation during emergency EGD? * Does it improve endoscopic field visibility and improve the success rate of initial endoscopic hemostasis？ * Does it reduce the operator's perceived workload or stress? Researchers will compare patients who received intravenous ondansetron with patients who received placebo to see if ondansetron can reduce patient discomfort and improve patient cooperation, therefore improve the quality of the procedure. Participants will receive either intravenous ondansetron and dyclonine hydrochloride mucilage or intravenous saline and dyclonine hydrochloride mucilage prior to the endoscopic procedure.

Inclusion Criteria: * Presence of suspected or confirmed upper gastrointestinal bleeding with an indication for emergent endoscopic intervention. * Capability to provide informed consent. Exclusion Criteria: * Presence of any contraindication to upper gastrointestinal endoscopy. * Concurrent severe primary diseases of the respiratory, cardio-cerebrovascular, renal, central nervous, or hematologic systems. * Pregnancy. * Presence of neuropsychiatric disorders, including severe depression or severe anxiety. * Presence of a known history of cardiac arrhythmia. * Allergic to dyclonine hydrochloride or ondansetron.