Femoral nerve blocks (FNBs) are used as safe and useful procedures to control severe
postoperative pain from
total knee arthroplasty (TKA). Various adjuvants have been used to prolong the duration of the
local anesthetic blockade. This study evaluated whether a low dose of
naloxone administered with
local anesthetics prolongs the duration of FNB. A prospective, randomized double-blind controlled study was conducted with 74 patients undergoing unilateral TKA. Through a single-bolus administration guided by ultrasound, the control group (group C) received 20 mL of 0.375%
ropivacaine, while the
naloxone group (group N) received 20 mL of 0.375%
ropivacaine with 100 ng of
naloxone. The time elapsed before the first
analgesia request, the total amount of
opioids consumed at 24 h postoperatively, the onset time of the sensory blockade, the visual analog
pain scale (VAS) scores after arriving at the recovery room, after 6, 12, 18, and 24 h at rest and after 12, 18, and 24 h of activity, the quadricep strength before the FNB procedure and at 12 and 24 h postoperatively, the quality of sleep on the first night after surgery, the satisfaction score, and the incidence of postoperative complications were recorded. The time elapsed before the first
analgesia request was significantly longer in group N (735.5 ± 187.2 min) than that in group C (602.6 ± 210.4 min) (P=0.003). The total dose of supplementary
opioids consumed at 24 h postoperatively was significantly lower in group N (312.4 ± 141.7 μg) than that in group C (456.5 ± 279.5 μg) (P=0.007). Lower VAS scores were recorded in group N than that in group C at rest and during knee activity (rest, 12 h, P=0.001, 18 h, P=0.043; activity, 12 h, P=0.001). The addition of a low dose of
naloxone to
ropivacaine for FNB significantly delayed the first request for rescue
analgesia and decreased the
opioid consumption within 24 h, without significant complications.