Liposomal Bupivacaine—A Boon for Opioid-Sparing Surgery?

Abstract

To the Editor It is with great interest that we read the article "Efficacy of Liposomal Bupivacaine and Bupivacaine Hydrochloride vs Bupivacaine Hydrochloride Alone as a Periarticular Anesthetic for Patients Undergoing Knee Replacement: A Randomized Clinical Trial." 1 We find it encouraging that this large, relatively homogeneous trial has confirmed that the traditional form of bupivacaine is comparable on multiple outcomes such as opioid use, adverse events, and long-term functional outcome. In addition to clinical outcomes, traditional bupivacaine is also shown to be significantly more cost-effective compared with the liposomal vehicle.We are intrigued by the suggestion by Hamilton et al 1 that certain subgroups may benefit from periarticular liposomal bupivacaine injections. Which subgroups might fall into this category? We wonder whether subgroups based on variation in surgical technique (ie, tourniquet application) 2 and patients' psychological factors (eg, pain catastrophizing, anxiety, depression) 3 may influence pain score and opioid consumption after knee replacement surgery.The potential implication of the differing pharmacokinetics of these 2 formulations are also of interest to us. Given the longer half-life of the liposomal bupivacaine, was longer observation required compared with traditional bupivacaine? Given that these patients were given more than double the dose of the bupivacaine hydrochloride, it seems feasible that toxicity would have been a concern. 4 Are there any data on occurrence or timing of any analgesia-related toxicity?Given the ultimate goal of opioid-free surgery, perhaps further investigation regarding higher dosages of the liposomal bupivacaine or differing mixture ratios of standard to liposomal bupivacaine may yield improvements in nonopioid postoperative pain management.