Effect of Two Different Volumes of Bupivacaine 0.25% Used in Ultrasound-guided Erector Spinae Plane (ESP) Block on Dermatome Spread: A Volume Study

The study will have a double-blind design and will be conducted after obtaining an approval from the local ethics committee. The study will include 50 patients planned for thoracotomy, aged 18-65 years with an ASA score of I-II. The patients will be randomized by sealed tender and will be divided into 2 groups with 25 patients each. Patients that will be transferred to the intensive care unit (ICU) intubated after the surgery, patients with a body mass index of 35 or over, patients detected with infection in the intervention site, patients with hematological diseases, patients with a known allergy to local anesthetics, patients that will not provide a written or verbal consent, pregnant patients, and patients with an ASA score of III or IV will be excluded from the study. All the patients will undergo physical examination and their laboratory parameters will be evaluated one day prior to the procedure. Moreover, on the same day, each patient will be informed about dermatome testing (hot/cold), pain prick test (pain test), and pain pump set. Age, body height and weight, duration of block, and duration of surgery will be recorded for each patient