Inclusion Criteria:  Patients undergoing elective cerebellopontine angle tumor surgery. Age ≥ 18 years old. ASA class I to III. All those who sign the informed consent form.  Exclusion Criteria:  Patients with severe heart disease (including patients with preoperative heart rate < 50 beats / min, severe arrhythmias, such as premature beats, paroxysmal supraventricular tachycardia, atrial flutter or fibrillation, patients with myocardial ischemia < 6 months, heart failure, myocarditis, pericarditis or cardiomyopathy). Patients unable to complete preoperative cardiac assessment. Patients with chronic kidney disease.