Adolescent idiopathic scoliosis (AIS) is a three-dimensional structural deformity of the spine, the etiology of which is not clearly known, and can be seen from the age of 10 until the skeletal system matures. The Scoliosis Research Society (SRS) defines AIS as vertebral rotation and a Cobb angle of 10° or greater. Its incidence varies between 0.47% and 5.2%. It is more common in women than in men. In patients with a Cobb angle greater than 40° or who are not yet bone-mature and who are continuously progressing, surgical intervention is often performed with posterior spinal fusion. Scoliosis negatively affects not only the appearance of patients but also their lung functions through differentiation in thoracic morphology and progression of spinal curvature. The severity of this restrictive pattern in lung functions can be assessed with pulmonary function tests (PFT). However, this test requires patient cooperation and is particularly difficult to perform in patients with cognitive dysfunction. Despite studies recommending the use of pulmonary function tests in preoperative risk assessment, the literature shows inconsistency in predicting the need for postoperative intubation and mechanical ventilation.

In this study, the effect of preoperative pulmonary function tests (PFT) performed before AIS surgery on the need for intensive care admission will be evaluated. In addition, the potential relationships between PFT results and intraoperative and postoperative blood transfusion needs, postoperative intubation needs, hospital stay, mortality status, inotropic support needs, Cobb angle, scoliosis location, and the number of affected vertebrae will be investigated.

After local ethics committee approval, patients' age, gender, weight, American Society of Anesthesiologists (ASA) physical status, additional diseases, localization of scoliosis, number of vertebrae affected, Cobb angle and presence of chronic lung disease will be recorded within the scope of demographic data.

Cobb angle or lateral spinal curvature will be measured and recorded on the spine radiograph closest to the date of surgery. In terms of preoperative respiratory function tests, the results performed closest to the date of surgery and accepted as successful according to American Thoracic Society standards will be analyzed. In this context, forced vital capacity (FVC) percentage of normal, forced expiratory volume in 1 second (FEV1) percentage of normal, and FEV1/FVC ratios will be recorded. In the presence of an obstructive or restrictive pattern, FEV1/FVC or FVC Z-scores will be examined and evaluated as normal, mild, moderate or severe in accordance with European Respiratory Society/American Thoracic Society (ERS/ATS) guidelines. The Z-score shows how much the individual's measured value deviates from the reference population determined according to factors such as ethnicity, gender, age, and height. A z-score greater than -1.645 is considered normal, a z-score between -1.645 and -2.5 is considered mild, a z-score between -2.5 and -4.0 is considered moderate, and a z-score below -4.0 is considered severe.

The recorded data will be evaluated by considering the need for intensive care admission, need for intraoperative and postoperative blood transfusion, need for postoperative intubation, length of hospital stay, mortality status, need for inotropic support, Cobb angle, location of scoliosis and number of affected vertebrae. Postoperative intubation status will be defined as patients brought to the ICU without extubation or re-intubated within 24 hours.

Inclusion Criteria:

• Age range 10-18
• Patients who underwent posterior spinal fusion surgery for Adolescent Idiopathic Scoliosis under general anesthesia

Exclusion Criteria:

• Body mass index >35 kg/m²
• ASA (American Society of Anesthesiologists) score of 4 and above
• Patients who have undergone revision surgery
• Patients with mental retardation
• Need for Bilevel Positive Airway Pressure (BPAP) before surgery
• Patients who could not successfully complete preoperative respiratory function tests
• Preoperative tracheostomy presence
• Patients with vertebral anomaly due to a secondary reason
• Patients with a diagnosed syndrome

Patients between the ages of 10-18 who underwent posterior spinal fusion surgery under general anesthesia due to Adolescent Idiopathic Scoliosis (AIS) will be included in the study. Exclusion criteria were determined as ASA (American Society of Anesthesiologists) score of 4 and above, body mass index >35 kg/m², mental retardation, Need for Bilevel Positive Airway Pressure (BPAP) before surgery, patients who could not successfully complete preoperative respiratory function tests, presence of tracheostomy and revision surgeries.