A Randomized Controlled Double-Blind Trial of Liposomal Bupivacaine Local Infiltration for Pain Control After Hemorrhoidectomy

INTERVENTION: Bupivacaine Liposome Hydrochloride Bupivacaine Combination Group:LB 266mg mixed with 75mg of bupivacaine hydrochloride solution, total 30ml;Control group:Bupivacaine hydrochloride 75 mg, diluted to 30 ml with 0.9% NS; CONDITION: Hemorrhoids PRIMARY OUTCOME: The area under the time curve (R‐AUC) of resting pain intensity scores (NRS scores) at 4, 8, 12, 24, 36, 48, and 72 hours after local perianal infiltration.; SECONDARY OUTCOME: Pain intensity scores (NRS scores) within 10 minutes after recovery from general anesthesia, before each administration of rescue analgesics, upon leaving the recovery room, and at 4h, 8h, 12h, 24h, 36h, 48h, and 72h after perianal local infiltration;Total opioid consumption (converted to morphine equivalents) at 12, 24, 48, and 72 hours after local perianal infiltration;Time to first use of opioid rescue medication within 72 hours after perianal local infiltration;Postoperative pain intensity score during defecation (NRS score);Postoperative pain relief satisfaction score (0–10 points, 0 being least satisfied, 10 being most satisfied); INCLUSION CRITERIA: 1. Age >= 18 years, BMI 18.0 30.0 kg/m^2, male weight > 50 kg, and non‐pregnant/non‐breastfeeding female weight > 45 kg; 2. Diagnosed with mixed hemorrhoids and scheduled for hemorrhoidectomy under general anesthesia, with an expected total incision length >= 3 cm. Single hemorrhoid incisions are mostly radial fusiform, approximately 1 2 cm in length; the total incision length is generally 1.5 5 cm (mostly 2 4 cm). A total incision length >= 3 cm indicates the need to treat at least two or more large hemorrhoids, resulting in a relatively large surgical wound and postoperative pain intensity reaching moderate or above (especially severe within 24 48 hours postoperatively). Selecting such patients ensures sufficient pain stimulus intensity to accurately evaluate the analgesic effect of liposomal bupivacaine versus bupivacaine hydrochloride mixture, as referenced in the literature; 3. ASA classification I III.