UC San Diego

Background

The authors evaluated the efficacy of liposome bupivacaine in a femoral nerve block (FNB) after total knee arthroplasty.

Methods

Part 1: subjects received FNB with 20 ml liposome bupivacaine (67, 133, or 266 mg) or placebo. Part 2: subjects were randomized to FNB with liposome bupivacaine 266 mg or placebo. The primary outcome measure was area under the curve of the numeric rating scale score for pain intensity at rest through 72 h (AUC NRS-R0-72) with imputed scores after rescue medication.

Results

In part 1, FNB with liposome bupivacaine 266 mg (n = 24) resulted in analgesia similar to that obtained with 133 mg and was chosen for part 2. In part 2, least-squares mean (standard error) AUC NRS-R0-72 was lower with liposome bupivacaine 266 mg (n = 92) than with placebo (n = 91; 419 [17] vs. 516 [17]; P < 0.0001). This outcome remained unchanged in a post hoc analysis without score imputation (221 [12] vs. 282 [12]; P = 0.0005). Least-squares mean AUC NRS-R with imputed scores was lower with liposome bupivacaine during each 24-h interval (0 to 24, 24 to 48, and 48 to 72 h) after surgery; AUC NRS-R without imputed scores was lower during the 0- to 24-h and 24- to 48-h intervals. The liposome bupivacaine group had lower mean total opioid use (76 vs. 103 mg morphine; P = 0.0016). Pain was sufficiently severe to require second-step rescue with opioids via intravenously administered patient-controlled analgesia in 92% of liposome bupivacaine patients and 81% of placebo patients. With patient-controlled analgesia and other forms of rescue analgesia, mean NRS scores with activity were moderate in both liposome bupivacaine and placebo groups throughout the part 2 study period. Incidence of adverse events was similar between the groups (part 1: 90 vs. 96%; part 2: 96 vs. 96%, respectively).

Conclusion

FNB with liposome bupivacaine (266 mg) resulted in modestly lower pain scores and reduced opioid requirements after surgery, with an adverse event profile similar to placebo.