Liposomal Bupivacaine versus Dexamethasone: Comment

The work of Kim et al. on liposomal bupivacaine in the setting of interscalene block for patients undergoing day care arthroscopic shoulder surgery interested us.¹  The dose of local anesthetic and the concentration used differed significantly. The liposomal group received 158 mg (133 mg plus 25 mg) of bupivacaine in 15 ml, a 1.05% concentration. However, only 75 mg bupivacaine was given in the standard group. Furthermore, dexamethasone use was not restricted to the comparator group. In addition to that used for the perineural blockade, dexamethasone was used to prevent postoperative nausea and vomiting at different dosing in both groups: 4 versus 8 mg in the standard and liposomal groups, respectively. As dexamethasone administered by intravenous and perineural routes extends the block duration, the main results in this study may warrant further consideration in this respect.² 

The authors discharged their patients an average of 90 min after surgery. While this shows commendable efficiency, we believe that aspects of monitoring and assessment might have been overlooked; motor block and assessment of phrenic nerve function are among them. Phrenic nerve palsy is common in this setting, and the authors’ record of Horner’s syndrome and hoarseness might suggest it was a possibility in the study cohort. Although the authors have excluded those with severe respiratory impairment, phrenic nerve palsy can invoke respiratory failure in even mild to moderate chronic obstructive pulmonary disease. Unilateral phrenic nerve palsy after interscalene block reduces the forced expiratory volume in 1 s, peak expiratory flow, and forced vital capacity as much as 40%.³  It would be interesting to know the follow-up protocol used and how anticipated problems were detected or offset.

An erratum has been published regarding Kim et al.: Anesthesiology 2022; 136:434–47, and a corrected version of the manuscript has been posted online.

The authors declare no competing interests.