IVC Collapsibility Index in Lumbar Stabilization Surgery

Inclusion Criteria: * Age ≥ 18 years * Patients classified as ASA physical status I-II-III * Patients scheduled for elective lumbar spine stabilization surgery under general anesthesia * Ability to obtain adequate inferior vena cava (IVC) ultrasonographic imaging * Provision of written informed consent Exclusion Criteria: * Age younger than 18 years * Emergency surgery * American Society of Anesthesiologists (ASA) physical status IV * Patients undergoing revision lumbar stabilization surgery * Baseline systolic blood pressure \>180 mmHg or \<90 mmHg * Heart failure with ejection fraction (EF) \<40% * Pulmonary artery pressure (PAP) \>40 mmHg * Presence of intra-abdominal mass, ascites, or increased intra-abdominal pressure * Body mass index (BMI) \>30 kg/m² * Pregnancy * Patients with neurological or psychiatric disorders * Inability to obtain adequate inferior vena cava (IVC) ultrasonographic imaging * Refusal to provide written informed consent