Anesthesia induction was achieved with propofol (2-3 mg kg-1), fentanyl (2 mcg kg-1), and rocuronium (0.6 mg kg-1). Anesthesia was maintained with Total intravenous anesthesia (TIVA) used remifentanil (0.25-0.5 mcg kg-1 min-1) and propofol (150 mcg kg-1 min-1). During maintenance, a fresh gas flow of 3 L with a mixture of 50% oxygen and 50% air was used. The BIS value was kept between 30-50.
Patients were divided into two groups according to a computer-based simple randomization method. Those who received a preoperative ESP block at the T4 vertebra level under ultrasound guidance were designated as Group I, while those who underwent surgery without the block were designated as Group II.
The ESP block was performed unilaterally in the direction of the surgery by the same anesthetist. Blocks were performed using an Esaote ultrasound device (Esaote My Lab 6 US machine, Florence, Italy), a multifrequency convex probe (1-8 MHz), and a 22-gauge, 50 mm facet needle (B. Braun Sonoplex, Melsungen, Germany) The block needle was placed at the level of the T4 spinal process using the in-plane approach, approximately 3 cm lateral to the T4 spinous process in the parasagittal plane. After visualizing the transverse process with the in-plane approach, the 50 mm facet needle (B. Braun Sonoplex, Melsungen, Germany) was inserted through the skin, and a test dose of 1 ml of 0.9% NaCl was injected between the fascia of the trapezius, rhomboid, and erector spinae muscles and the transverse vertebral process to confirm the location. A total of 20 ml of 0.5% bupivacaine was used as a local anesthetic. The cranial and caudal spread of the local anesthetic was monitored.
