Ultrasound-guided bilateral block
ESPB
STERILE
After induction, the patient was changed to a prone position. The skin was disinfected with iodophor, and the high-frequency linear ultrasound probe (6–13 Mhz, SonoSite S Series, USA) was placed in a sterile sleeve. The probe was placed longitudinally at the 12th rib of the midscapular line and moved inward along the 12th rib until the tip of the transverse process was reached. Using an in-plane method, the needle (0.71 × 120 mm, 22 G, B Braun, Germany) was inserted into the skin at the head of the probe until it reached the transverse process. Two milliliters of normal saline (NaCl 0.9%) were injected to identify the needle tip position. If the needle tip was located between the transverse process and the ESM and was not in the muscle, 20 mL 0.4% ropivacaine (AstraZeneca AB, Sweden) was injected immediately (Fig. 
Ultrasound images of ESPB with the in-plane technique. Arrows, needle shaft. Abbreviations: ESM, erector spinae muscle; TP, transverse process