To investigate the efficacy of two different regimens of local anesthetic boluses for continuous adductor canal block under ultrasound-guidance in total knee arthroplasty at King Chulalongkorn Memorial Hospital.

Total knee arthroplasty (TKA) is a commonly performed surgical procedure for patients with severe knee osteoarthritis. However, one of the challenges associated with TKA is the significant postoperative pain experienced by patients, which can delay early mobilization and physical therapy. Uncontrolled pain worsens patient outcomes and healthcare costs as it can increase the risk of complications after surgery. Therefore, effective pain management is important for optimizing patient outcomes and promoting a smooth recovery process.Despite the absence of a standardized recommendation for the volume and concentration of bolus administration in continuous adductor canal block (CACB), many previous studies, have demonstrated the efficacy of a high-dose bolus followed by a low-concentration local anesthetic infusion for CACB. However, these trials exhibited differences in the doses and volumes of bolus injection. Therefore, the necessity of high concentration and volume bolus CACB in combination with comprehensive multimodal analgesia and LIA for postoperative pain management in TKA remains uncertain. The aim of this study is to investigate the efficacy of two different regimens of local anesthetic used in boluses for continuous adductor canal block under ultrasound-guidance in total knee arthroplasty at King Chulalongkorn Memorial Hospital.

Inclusion Criteria:

• Patients undergoing TKA aged more than 18 years
• Patients with American Society of Anesthesiologists (ASA) class 1-3
• Patients with body weight index (BMI) 18-40 kg/m2

Exclusion Criteria

• Patient refusal to participate
• Patients with known allergic to medications used in the research protocol
• Patients with contraindications to neuraxial or regional anesthesia, including existing neuropathy or neurological deficits involving the lower extremities, coagulopathy or bleeding diathesis and local skin infections
• Patients with contraindications to NSAIDs such as history of coronary artery bypass graft surgery, congestive heart failure, stroke, gastrointestinal bleedings or ulceration, asthma, hepatic and renal disease, abnormal coagulation, or pregnancy
• Patients with chronic opioid use (opioids have been used daily or almost daily for more than three months or sixty milligrams or more of morphine has been used daily for more than one month) or diagnosed with neuropathic pain
• Patients that are unable to perform preoperative Quantitative sensory testing.