Femoral nerve block with 0.25% or 0.5% bupivacaine improves postoperative analgesia following outpatient arthroscopic anterior cruciate ligament repair

Background and Objectives: Femoral nerve block is effective in reducing pos toperative pain after inpatient knee surgery. We studied its efficacy compa red with standard analgesia following outpatient anterior cruciate ligament repair, including the duration of analgesia and the effect of different co ncentrations of bupivacaine. Methods: After Institutional Review Board approval and informed consent, we prospectively randomized patients to receive, in a blinded fashion, either a sham block, a femoral nerve block with 25 mt 0.25% bupivacaine, or with 25 mL 0.5 % bupivacaine after anterior cruciate ligament repair under epidu ral anesthesia. Verbal analog pain scores were evaluated by a blinded obser ver at 20 and 40 minutes after injection. Patients with pain >4 (out of 10) were assessed for the presence of a block and offered a supplemental block if no anesthesia was present at either evaluation. By prospective agreemen t, any study group with 6 failures was excluded from further recruitment. A fter discharge, patients recorded pain scores and analgesic consumption in a diary, and estimated the time at which they perceived that analgesia and sensory block from the femoral nerve block resolved, based on an increase i n pain, sensation, and strength in the leg. Results: in the sham block group, 6 of 12 patients reported inadequate anal gesia in the postanesthesia care unit (4 at 20 minutes, 2 at 40 minutes; gr eater than other groups, P < .003) and were excluded from further study. Pa tients with sham blocks had higher pain scores 20 minutes after the block, and requested intravenous analgesia more often. Bupivacaine 0.25% and 0.5% provided 23.2 +/- 7 and 25.7 +/- 11 hours of analgesia, respectively. Conclusions: Femoral nerve block with 0.25% bupivacaine contributes signifi cantly to multimodal postoperative analgesia in the immediate postoperative period following outpatient anterior cruciate ligament repair. Both doses of bupivacaine studied provided analgesia for the first night after surgery .