The study is planned to include patients who will undergo elective scoliosis surgery under general anesthesia at the Health Sciences University Antalya Education and Research Hospital. Demographic data including age, gender, height, weight, and ASA score of the patients will be recorded before general anesthesia. ECG, oxygen saturation, and non-invasive blood pressure will be monitored while the patients are lying supine before general anesthesia. An esophageal temperature probe will be placed before being placed in the prone position. All patients will receive standard anesthesia management. After being placed in the prone position, patients will be warmed with heaters containing an air-blowing system during the operation to prevent hypothermia. Anesthesia will be maintained with total intravenous anesthesia as a controlled infusion. Rainbow sensors will be placed on the 4th fingertips of the non-dominant hand of the patients and connected to the Radical-7 Pulse CO-Oximeter device and the initial Hb value will be recorded routinely and recorded hourly during the operation. Hemogram samples will be studied in the laboratory. During the operation, every hour and at the end of the operation, SpHb value, Hb, Hct levels in hemogram will be recorded. At the end of the operation, the amount of intraoperative blood transfusion, the amount of crystalloid and colloid given, the duration of the operation, the duration of anesthesia, urine output, and the need for vasopressors will be routinely recorded. A database will be created in a computer environment from this information.

Inclusion Criteria:

• Preoperative hemoglobin ≥ 9 g/dL
• ASA I - III

Exclusion Criteria:

• Patients with hematological disease,
• Uncorrected preoperative anemia (preoperative hemoglobin < 9 g/dL)

Patients who apply to our hospital's orthopedic clinics to undergo elective scoliosis surgery.