The analgesic efficacy of the continuous adductor canal block compared to continuous intravenous fentanyl infusion with a single-shot adductor canal block in total knee arthroplasty: a randomized controlled trial

Abstract

Background: The adductor canal block (ACB) is an effective intervention for postoperative analgesia following total knee arthroplasty (TKA). However, the ideal ACB regimen has not yet been established. We compared the analgesic effects between a continuous ACB group and fentanyl-based intravenous patient-controlled analgesia (IV-PCA) with a single-shot ACB group.

Methods: Patients who underwent TKA were randomly allocated to either a continuous ACB group (Group CACB) or IV-PCA with a single-shot ACB group (Group IVACB). Before the surgery, ultrasound guided ACB with 0.5% ropivacaine 20 cc was provided to all patients. Before skin incision, the infusion system (0.2% ropivacaine through an adductor canal catheter in group CACB vs. intravenous fentanyl in group IVACB) was connected. The postoperative pain severity; the side effects of local anesthetics and opioids; administration of rescue analgesics and anti-emetics; and sensorimotor deficits were measured.

Results: Postoperative pain severity was significantly higher in the IVACB group at 30 min, 4 h, 24 h, and 48 h after surgery. The averages and standard deviations (SD) of the NRS score of postoperative pain were 0.14 ± 0.37, 4.57 ± 2.37, 6.00 ± 1.63, and 4.28 ± 1.49, respectively in the IVACB group. Rescue analgesic requirements and quadriceps muscle strength were not statistically different between the groups throughout the postoperative period. Moreover, rescue antiemetic requirements were higher in group IVACB than group CACB.

Conclusions: In this study, the continuous ACB provided superior analgesia and fewer side effects without any significant motor deficit than the IV-PCA with a single-shot ACB.

Keywords: Analgesia; Fentanyl; Knee replacement arthroplasty; Local anesthetics; Nausea; Opioid; Pain management; Patient controlled analgesia; Postoperative pain; Ropivacaine; Vomiting.

Fig. 1. CONSORT flow diagram.

Fig. 2. Changes in numeric rating scale perioperative pain severity. NRS: numeric rating scale, CACB: continuous adductor canal block, IVACB: intravenous patient-controlled analgesia with adductor canal block, Pre: before ACB, Post: 30 minutes after ACB, 30 min: 30 minutes after surgery, 2 h: 2 hours after surgery, 4 h: 4 hours after surgery, 8 h: 8 hours after surgery, 24 h: 24 hours after surgery, 48 h: 48 hours after surgery. ^*P < 0.05 compared with Group IVACB.

Fig. 3. Morphine equi-analgesic dose of rescue analgesics. CACB: continuous adductor canal block, IVACB: intravenous patient-controlled analgesia with adductor canal block, 30 min: 30 minutes after surgery, 2 h: 2 hours after surgery, 4 h: 4 hours after surgery, 8 h: 8 hours after surgery, 24 h: 24 hours after surgery, 48 h: 48 hours after surgery. Morphine equi-analgesic dose of each time points were the summed dosage from the end of last measurement up to the current measurement.

Fig. 4. Medical Research Council scale of quadriceps muscle strength. CACB: continuous adductor canal block, IVACB: intravenous patient-controlled analgesia with adductor canal block, Pre-op: 1 day before surgery, POD 1: postoperative day 1, POD 2: postoperative day 2, POD 3: postoperative day 3, POD 4: postoperative day 4.