Radical mastectomy is currently the mainstream surgical treatment for breast cancer. Patients often experience significant postoperative pain, and some may develop chronic pain. General anesthesia is commonly used, with remifentanil being the most frequently used intraoperative analgesic. However, prolonged high-dose use of remifentanil can induce opioid-induced hyperalgesia (OIH). Previous studies have shown that serratus anterior plane block can reduce acute postoperative pain after radical mastectomy, but it remains unclear whether it can reduce postoperative pain sensitization and the incidence of chronic pain. Liposomal bupivacaine is a new long-acting local anesthetic with an effect lasting up to 72 hours. This study aims to investigate the effect of liposomal bupivacaine serratus anterior plane block on postoperative pain sensitization and chronic pain in patients undergoing radical mastectomy, providing a reference for clinical treatment. The study includes 120 participants. A tactile measurement kit is used to measure the mechanical pain threshold around the surgical incision preoperatively and at 24 and 48 hours postoperatively, as well as postoperative persistent pain scores at 7 days, 1 month, 3 months, and 6 months. The data will then be analyzed to draw conclusions.
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Crossover
Serratus Plane block (single injection)
Procedure/SurgeryAfter anesthesia induction, the same experienced anesthesiologist performed an ultrasound-guided serratus anterior plane block on the surgical side. The skin was routinely disinfected and draped. A linear 10-13 MHz ultrasound probe was used to locate the 5th rib along the mid-axillary line to identify the superficial latissimus dorsi and the deep serratus anterior muscles. A 22G (80 mm) nerve block needle was inserted in-plane from anterolateral to posteroinferior. When the needle tip reached the surface of the serratus anterior muscle, with clear visualization of the tip in place, no aspiration of fluid, and no air, a test dose of 2 ml was first administered. After a hypoechoic area was observed on the ultrasound, and no blood or air was aspirated again, 20 ml of 0.375% ropivacaine was slowly injected in the ropivacaine group, 20 ml of 0.665% liposomal bupivacaine in the liposomal bupivacaine group, and 20 ml of saline in the placebo group, with real-time ultrasound visualization of t
Mechanical pain threshold around the postoperative incision
Tactile measurement kits (Von Frey filaments) were used to assess patients' mechanical pain detection thresholds around the surgical incision area and the forearm preoperatively (T1), 24 hours postoperatively (T2), and 48 hours postoperatively (T3). The method for measuring mechanical pain thresholds involved measuring the threshold around the incision at two points 2 cm from either end of the incision and one point 2 cm below the middle of the incision, with the average of the three points taken as the final value. For the forearm, measurements were taken at points 3, 6, and 9 cm from the midpoint of the elbow, and the average of these three points was calculated similarly. The tactile measurement kit consists of filaments of varying thicknesses, with the filament weight corresponding to different levels of mechanical stimulus intensity.
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