The investigators aimed to compare the effects of ultrasound guided erector spina plan block and posterior quadratus lumborum block on intraoperative and postoperative opioid consumption in patients who will undergo short segment lumbar stabilization surgery.

All participants will be monitored with ECG, SpO2, non-invasive blood pressure. In induction, 1mg/kg 2% lidocaine, 2-3mg/kg propofol, 1mcg/kg fentanyl, 2mg midazolam, 0.6 mg/kg rocuronium will be used. Anesthesia depth will be monitored with BIS (bispectral index), and anesthesia will be maintained with 50% oxygen-air mixture and sevoflurane. After patient intubation, invasive artery cannulation will be performed on the non-dominant hand, and the patients will be placed in a prone position. 20 cc bupivacaine of 0.25% will be administered to both regions bilaterally, by following the rules of asepsis, with a 10 cm pajunk needle accompanied by USG, the needle site will be confirmed with 3 mm saline.

BIS will be kept in the range of 40-50 throughout the case, and invasive arterial monitoring will be performed. 1 g paracetamol, 1 mg/kg tramadol and 4 mg ondansetron will be administered to the patients 30 minutes before the end of the surgery.

After appropriate extubation and wakefulness, patients will be transferred to the postoperative anesthesia care unit (PACU), where they will be followed for 24 hours.

An intravenous (IV) patient-controlled analgesia device (PCA) containing 100ml of tramadol at a concentration of 4mg/cc will be inserted. No infusion will be given, and the bolus dose will be set to 20mg, with a lock time of 20 minutes. In the postoperative period, 50 mg of dexketoprofen will be administered every 8 hours.

VAS values, vital signs, and possible opioid side effects of the patients at 0, 1, 2, 6, 12 and 24 hours will be recorded. After completing 24 hours, the patient will be separated from the IV PCA device and transferred to the service.

Inclusion Criteria:

• Patients who will undergo lumbar stabilization operation
• Between the ages of 18-65
• Both genders
• ASA I-III risk group

Exclusion Criteria:

• Patients who did not accept the study
• Patients younger than 18 years old
• Patients older than 65 years
• Patients with an ASA score greater than III
• Patients with an active infection in the area to be blocked
• Patients with a long bleeding time
• Those who are pregnant
• Patients with kidney failure
• Patients with liver failure
• Patients with BMI<18 and BMI>30
• Those who are allergic to local anesthetics
• Patients who have had previous lumbar surgery
• Uncooperative or mentally retarded patients

Patients who will undergo lumbar stabilization operation under general anesthesia in Ankara Bilkent City Hospital Operating Room, between the ages of 18-65, both genders, and in the ASA I-III risk group will be included in the study.