Overview

Anal Fistula refers to an abnormal infectious fistula tract between the anorectum and the perianal skin. The prevalence of anal fistula is approximately 8.6 cases per 100,000 individuals. It can occur at any age but is relatively more common in individuals aged 20-40 years, with a higher incidence in males than females.

Postoperative wound management is a critical component of the overall treatment for anal fistula patients. Regular postoperative wound care, such as dressing changes, can reduce recurrence rates, alleviate pain, and shorten hospitalization time. However, postoperative pain remains a major challenge in wound management following anal fistula surgery. This is largely attributed to inadequate current postoperative analgesic protocols.

With ongoing advancements in local anesthetics, liposomal bupivacaine has been applied for postoperative analgesia. It offers higher bioavailability and a prolonged half-life, providing up to 72 hours of sustained analgesic effect. Given the limitations of existing analgesic strategies for post-anal fistula surgery, developing more effective pain management approaches to reduce postoperative pain holds significant clinical importance.

Therefore, the investigators propose that a repeat-dosing strategy based on liposomal bupivacaine may provide superior postoperative pain control for anal fistula patients. To investigate this, the investigators designed a prospective, multicenter, randomized, open-label, controlled clinical trial. This study aims to evaluate the efficacy and safety of repeat-dose liposomal bupivacaine for postoperative analgesia following anal fistula surgery, thereby generating high-level evidence to support its clinical application in this context.

Eligibility

Inclusion Criteria:

• Diagnosed with anal fistula and scheduled to undergo anal fistula surgery;
• Aged between 18 and 60 years;
• ASA (American Society of Anesthesiologists) physical status class I-II;
• Patient provides written informed consent after understanding the study protocol.

Exclusion Criteria:

• Anal fistula caused by specific etiologies (e.g., tuberculosis);
• Concurrent acute perianal skin infection;
• Poorly controlled diabetes (HbA1c >9%);
• Chronic use of corticosteroids;
• History of radiotherapy or chemotherapy within the past 2 weeks;
• Pregnancy or lactation;
• Hypersensitivity to local anesthetics or any component of the investigational drug;
• History of substance abuse, illicit drug use, or alcohol abuse;
• Use or planned use of non-opioid/opioid analgesics within 12 hours before/during surgery;
• Concurrent treatment with anticonvulsants, MAO inhibitors, antidepressants, neuromuscular blockers, or anticholinergics within 2 weeks prior to surgery;
• Severe hepatic/renal impairment, cardiopulmonary dysfunction, coagulation disorders, or comorbidities contraindicating surgery;
• History of severe psychiatric disorders or cognitive impairment;
• Sensory disorders (e.g., hyperalgesia) or preexisting pain interfering with postoperative pain assessment;
• Contraindications to amide-type local anesthetics, opioids, or propofol;
• Participation in investigational drug trials within 90 days prior to enrollment;
• Other clinical/laboratory conditions deemed by investigators to preclude trial participation.