To Compare the Effects of 0.2% Ropivacaine Continuous Infusion versus Programmed Intermittent Bolus on Postoperative Analgesia with Adductor Canal Block, in Patients Undergoing Unilateral Knee Arthroplasty: A Randomized Controlled Trial

Abstract

Background: Multimodal regimens are the mainstay of postoperative analgesia. Analgesic effectiveness of programmed intermittent bolus (PIB) versus continuous infusion (CI) in ultrasound-guided adductor canal block (ACB) for unilateral knee arthroplasty, were compared. Materials and Methods: Following Ethical and Clinical Trials Registry approval, eligible patients were administered pericapsular infiltration, intraoperatively and ACB with catheter, postoperatively. As per randomization, the PIB group received 10 ml 0.2% ropivacaine every 3 hourly while the CI group received 6mL/h. In addition, both groups received patient controlled boluses of 5mL with lockout interval of 30 minutes. The numerical rating score (NRS) score, plasma concentration of ropivacaine, use of rescue analgesics, quadricep strength by Straight Leg Rising Test (SLRT), Medical Research Council (MRC) scale for motor power, were monitored at 0, 1, 4, 24, 48 h, and Likert Scale for patient satisfaction, was measured at 72 h. To be clinically meaningful, sample size calculation, was according to a difference in NRS, for a power of 0.80, and σ‐standard deviation of two points, thus requiring at least 17 patients in each group. Results: In PIB group, patients experienced better analgesia in the first 24 h (rest - 95% CI - 0.089–0.669, P = 0.010 and movement - 95% CI - 0.82–0.884, P = 0.018) and motor power, in the first (P = 0.051) and 4th h (P = 0.034), after recovery, along with improved patient satisfaction (P = 0.001). Ropivacaine plasma concentration, at regular intervals, was independent of the pain scores with rest and movement. Rescue analgesia was inconclusive in both groups. Conclusion: The PIB option provided better analgesia in the postoperative period.