Effects of continuous femoral nerve block combined with infiltration anesthesia on postoperative analgesia in patients undergoing total knee arthroplasty

Objective To evaluate the effects of continuous femoral nerve block combined with infiltration anesthesia on postoperative analgesia in the patients undergoing total knee arthroplasty. Methods Ninety patients, aged 50-80 yr, weighing 45-90 kg, of ASA physical status Ⅰ-Ⅲ, scheduled for elective unilateral total knee arthroplasty, were randomly divided into 3 groups (n=30 each) using a random number table: continuous femoral nerve block + infiltration anesthesia group (group A) ; continuous femoral nerve block group (group B) ; continuous femoral nerve block + single sciatic nerve block group (group C) . The femoral nerve was catheterized for block before induction of general anesthesia in the three groups, and then a single sciatic nerve block was performed in group C. In group A, 20 ml mixture was injected into the posterior part of the joint capsule before prosthesis implantation, and 20 ml mixture was injected around the collateral ligaments and incision sites after prosthesis implantation and before closing.The mixture included ropivacaine 2.5 mg/ml, fentanyl 2.5 μg/ml, and methylprednisolone 1 mg/ml.In group B, 40 ml of normal saline was given as the method previously described in group A. Patient-controlled analgesia with 0.2% ropivacaine 250 ml was used for postoperative analgesia, lasting for 48 h. The patient-controlled analgesia pump was set up with a 5 ml bolus dose, a 30 min lockout interval and background infusion at a rate of 5 ml/h.Tramadol was used as rescue analgesic and was given orally to maintain the VAS score ≤ 5.VAS scores at rest were recorded at 4, 8, 12, 24 and 48 h after surgery, and VAS scores during activity were recorded at 8, 12, 24 and 48 h after surgery.The total consumption of tramadol within 48 h after surgery was recorded.The motor function of the affected extremity was assessed and scored at 12, 24 and 48 h after surgery, and the sensory and motor function was evaluated at 72 h after removal of the catheter.The occurrence of bleeding or exudates from the site of catheterization and adverse effects were recorded. Results Compared with group B or C, VAS scores at rest at 4-24 h after operation, VAS scores during activity at 8-24 h after operation, and the total consumption of tramadol were significantly decreased in group A. Compared with group B, no significant changes were found in motor block score of the affected extremity in group A. Compared with group C, the motor block score of the affected extremity was significantly decreased in A and B groups.There were no significant differences in the incidence of bleeding or exudates from the site of catheterization and nausea and vomiting between the three groups. Conclusion Continuous femoral nerve block combined with infiltration anesthesia can provide sufficient analgesia without influencing the recovery of sensory and motor function, and the safety is good for the patients undergoing total knee arthroplasty. Key words: Femoral nerve; Nerve block; Anesthesia, local; Pain, postoperative; Analgesia; Arthroplasty, replacement, knee