Comparison of the Inflammatory Response in Patients Undergoing Surgery for Degenerative Spinal Diseases: Sevoflurane-Based Balanced Anesthesia Versus Target-Controlled Propofol Infusion (TCI)

Patients undergoing surgical treatment for degenerative spinal disease will be randomly assigned to two groups.

The first group will receive balanced anesthesia. Anesthesia will be induced using propofol, fentanyl, and a neuromuscular blocking agent, most commonly atracurium, while hypnosis will be maintained using an inhaled mixture of sevoflurane, oxygen, and air.

The second group will receive total intravenous anesthesia (TIVA). Anesthesia will be induced in the same manner as in the first group, while hypnosis during surgery will be maintained by a continuous infusion of propofol, adjusted according to the target plasma concentration of propofol (target-controlled infusion anesthesia - TCI anesthesia), with an oxygen-air mixture.

All patients will have their comorbidities documented, with particular emphasis on obesity, arterial hypertension, hypercholesterolemia, and diabetes mellitus. Their American Society of Anesthesiologists (ASA) physical status classification will also be recorded.

Patients' sex, body weight, and height will be recorded, and their body mass index (BMI) will be calculated.

Before transfer to the operating room, all participants will receive premedication with midazolam at a dose of 0.02-0.04 mg/kg. Antibiotic prophylaxis with a first-generation cephalosporin will be administered and repeated every three hours.

Preoperative baseline levels of hemoglobin, hematocrit, leukocytes, C-reactive protein (CRP), interleukin-6 (IL-6), ferritin, blood glucose, creatine kinase (CK), myoglobin, and cholesterol will be measured. The same laboratory parameters will be assessed on the first and second postoperative days, and changes in their values over time will be recorded. Intraoperative blood glucose levels will also be monitored.

The need for blood product transfusion will be documented.

The depth of anesthesia will be monitored intraoperatively using entropy monitoring, and anesthetic doses will be adjusted to maintain entropy values between 40 and 60.

An arterial catheter will be inserted in all patients for invasive arterial blood pressure monitoring. Blood pressure will be maintained within 30% of the initial recorded value. Hypotension will be treated with ephedrine and/or norepinephrine. The administration of these medications will be documented and compared between the two groups.

Normal saline and other balanced crystalloid solutions will be used for intraoperative fluid replacement.

Before the end of surgery, all patients will receive analgesics for postoperative pain management. Antiemetic medications will also be administered, and the incidence of postoperative nausea and vomiting will be recorded.

Pain levels will be assessed before and after surgery. The duration of anesthesia will be documented. Pain intensity will be measured using the Visual Analog Scale (VAS).

The incidence of postoperative surgical site infections will also be monitored.

**Exclusion criteria** will include patients under 18 years of age, emergency surgical procedures, surgery for malignant diseases, and patients with contraindications to cephalosporins or any of the anesthetic agents used in the study.

The planned duration of the study is one to two years.

All surgical procedures will be performed in the neurosurgical operating room of the University Clinical Hospital Mostar. Intraoperative computed tomography (CT) with navigation will be used to ensure more precise placement of spinal implants.