[Femoral nerve block for postoperative analgesia after anterior cruciate ligament reconstruction: comparison of 2 concentrations of bupivacaine with clonidine in 3 modes of administration]

Abstract

Background: The continuous femoral nerve block is used for postoperative orthopedic analgesia.

Objective: To evaluate 2 concentrations of bupivacaine with clonidine in 3 methods of administration for performing a continuous femoral nerve block.

Material and methods: Randomized controlled trial in ASA 1-2 patients in 6 groups. In groups 1, 2, and 3, the combination used was 0.125% bupivacaine plus clonidine. In groups la, 2a, and 3a, the combination was 0.0625% bupivacaine plus clonidine. Methods of administration were as follows: groups 1 and la, 10 mL x h(-1) in continuous infusion; groups 2 and 2a, 5 mL h x (-1) in continuous infusion plus 2.5 mL every 30 minutes through a patient-controlled analgesia (PCA) system; groups 3 and 3a, 5 mL every 30 minutes in a PCA system. Pain on a visual analog scale (VAS) and amounts of bupivacaine and morphine used were recorded 2 and 48 hours after surgery.

Results: A total of 105 patients were enrolled: 17 in group 1, 18 in group la, 18 in group 2, 17 in group 2a, 17 in group 3, and 18 in group 3a. No significant differences between any of the 6 groups were observed for patient characteristics, postoperative VAS scores, or morphine use.

Conclusions: A continuous femoral nerve block is useful for managing pain after anterior cruciate ligament surgery. The application of 5 mL x h(-1) in continuous infusion or in PCA system bolus doses provides excellent postoperative analgesia. Use of 0.0625% bupivacaine decreases overall consumption of analgesic and is not detrimental to quality of analgesia.