2.6. Erector Spinae Plane (ESP) Block Technique
STERILE, DECUBITUS
For this study, we performed the bilateral ESP block technique, which involves the patient sitting with support from a member of the care team or lying in a lateral decubitus position. Before each case, we did a preliminary scan with a linear ultrasound transducer (6–13 MHz) placed vertically on the patient's upper back, 2.5–3 cm lateral to midline. For sensory blockade of the appropriate dermatome, blocks were administered at levels T6–T10 for upper abdominal surgery and levels T8–L2 for lower abdominal incisions. The midline (spinous processes) and transverse processes were then marked bilaterally. Using a sterile technique, an 80 mm 22 G needle was inserted in cranial-caudal direction in-plane to the ultrasound transducer towards the transverse process. The needle crosses three layers of muscle, from posterior to anterior: trapezius, rhomboid, and erector spinae, until it touches the transverse process (