In the experimental group, norepinephrine at a concentration of 5 mcg/ml is preemptively administered through peripheral venous catheter with a size of 20 G or more from the time of anesthesia induction to the end of anesthetic administration. The norepinephrine is not preemptively administered in the control group. For anesthesia, total intravenous anesthesia using propofol and remifentanil is performed. During anesthesia, the injection rate of the test drug is allowed to be adjusted according to the blood pressure within the permissible range, and anesthesia management such as fluid infusion, blood transfusions, and drug administration is performed according to the judgment of the anesthesiologist, and there are no restrictions.

The achievement of hemodynamic stability during anesthesia is judged by the percentage (%) of the time when the target blood pressure falls outside of 90-110%, 80-120%, and 70-130% of the target blood pressure during the total anesthesia duration. The number of hemodynamic unstability occurred, and the number of patients with hemodynamic unstability are also sought. The incidence of postoperative complications between the two groups is also compared.

Inclusion Criteria:

Patients aged 20 to 65 who undergo elective craniotomy for brain tumor resection

Exclusion Criteria:

1. emergency surgery
2. If the subject includes those who cannot read the consent form (e.g. illiterate, foreigners, etc.)
3. cognitive dysfunction
4. pregnant, lactating
5. Congestive heart failure (New York Heart Association scores ≥3)
6. arrhythmia
7. Renal dysfunction (estimated Glomerular Filtration Rate less than 30 ml/min/1.73m2)
8. Patients with severe respiratory disease (pneumonia, chronic obstructive pulmonary disease, asthma under treatment, etc.)
9. Uncontrolled hypertension (baseline blood pressure greater than 140/90)