Dexmedetomidine is a highly selective alpha2-adrenergic receptor agonist with sedative, analgesic, anti-anxiety, and inhibitory sympathetic nerve excitation properties. It is commonly used in clinical anesthesia and intensive care.Radical gastrectomy for gastrointestinal malignant tumors is a common major operation in clinical practice, with long operation time, great trauma and strong stress response of patients. Dexmedetomidine is often used in general anesthesia during such operations, but its long-term use or large dose may produce certain side effects.Common side effects of dexmedetomidine include bradycardia and hypotension, etc. Previous studies have reported that dexmedetomidine can prolong QT interval and is at risk of causing tip torsion type ventricular tachycardia.Abnormal Potassium may affect myocardial repolarization and increase the risk of tip torsion ventricular tachycardia.The main purpose of this study was to observe the effects of long-term use of dexmedetomidine on perioperative internal environment such as electrolyte and rehabilitation indicators during radical general anesthesia for gastrointestinal malignancy, and the secondary purpose was to explore the optimal dose of dexmedetomidine for general anesthesia for patients undergoing radical general anesthesia for gastrointestinal malignancy.

Inclusion Criteria:

1. American Society of Anesthesiologists (ASA) physical status I or II;
2. age between 50-75 years, and a body mass index (BMI) between 18.5-28 kg/m2.

Exclusion Criteria:

1. Patients whoused hormones or drugs that have a hypoglycemic nature during the preoperative state, or had bradycardia, arrhythmia, hypotension, abnormal liver or kidney function, pancreatic disease, neuroendocrine malignancy, intraoperative blood transfusion;
2. Patients who refused participation and those who needed intensive care after the surgery were also excluded from the study;
3. Patients who had severe internal environmental disorders.