Serratus posterior superior intercostal plane block is the intervention used in this study. It was performed when the patient is in lateral decubitis position. A high frequency (7-12 MHz) linear transducer of the ultrasound device is placed at the spinae scapula level in the transverse plane, and the upper medial border of the scapula, the trapezius muscle, rhomboid muscle, serratus posterior superior muscle (SPSM) and the second and third ribs are visualized. The sonovisible needle is then advanced immediately medial to the scapula, aiming for the area between the second and third ribs in order to reach the fascial plane between the SPSM and intercostal muscles. After contact of the needle with the rib gently, 1-2mL of saline is used to confirm the correct plane, and a total of 30 mL of 0.25% bupivacaine is administered to the superficial to the intercostal muscle. PCA device was also performed to this group with the same protocol which was detailed in control arm.

Control group patients were not subjected to any block or local infiltration anesthesia (local anesthetic administration around the incision). Their postoperative pain was relieved with tramadol (intravenous analgesic drug) administration by using patient-controlled analgesia (PCA) device. Patient-controlled analgesia was achieved with tramadol hydrochloride at a concentration of 4 mg per 1 ml with the PCA device. The PCA device was configured to administer the patients boluses of 10 mg tramadol hydrochloride with a lockout time of 20 minutes, allowing a maximum of 4 pushes per hour. The total dose was standardized for all patients with a maximum daily dose of 400 mg and a maximum dose of 100 mg tramadol hydrochloride every 6 hours.

Serratus posterior superior intercostal plane block is the intervention used in this study. It was performed when the patient is in lateral decubitis position. A high frequency (7-12 MHz) linear transducer of the ultrasound device is placed at the spinae scapula level in the transverse plane, and the upper medial border of the scapula, the trapezius muscle, rhomboid muscle, serratus posterior superior muscle (SPSM) and the second and third ribs are visualized. The sonovisible needle is then advanced immediately medial to the scapula, aiming for the area between the second and third ribs in order to reach the fascial plane between the SPSM and intercostal muscles. After contact of the needle with the rib gently, 1-2mL of saline is used to confirm the correct plane, and a total of 30 mL of 0.25% bupivacaine is administered to the superficial to the intercostal muscle.

Numerical rating scale is used for pain assessment. The scores of the numerical rating scale changes between 0 to 10 points. 10 points mean "the most severe pain that the patient ever had". 0 point means "there is no pain." Higher scores mean worse outcome.

Postoperative analgesic (tramadol) need is measured by using patient-controlled analgesia (PCA) device.