Perineural Safety of Dexamethasone Plus Local Anesthetic , and Possible Augmentation of Rebound Pain by Perineural Dexamethasone Plus Local Anesthetic

May 2014 • Volume 118 • Number 5 Copyright © 2014 International Anesthesia Research Society DOI: 10.1213/ANE.0000000000000203 Since the 1990s, the subspecialty of ambulatory regional anesthesiology has pursued research addressing “off-label” and/or novel use of traditional medications in new, if not routine, multimodal contexts. Multimodal antiemetic prophylaxis (with 5-HT3 antagonists, dexamethasone, and a nonsedating dopaminergic antagonist) is now generally expected, whether1,2 or not3–5 based on predicted risk factors for postoperative nausea and vomiting. More recently, the use of perineural analgesic adjuvants has been explored, including agents such as dexmedetomidine,6,7 clonidine, buprenorphine, and dexamethasone (C-B-D).8–10 The goals of multimodal perineural analgesia include the potential to extend nerve block analgesic duration while potentially reducing the needed concentration of local anesthetics to provide meaningful analgesia, while simultaneously reducing the potential need for a perineural continuous infusion catheter. Dexamethasone is a common denominator in both multimodal pursuits of antiemesis and perineural analgesia and is also frequently explored as a meaningful coanalgesic for systemic use.11–13 The article by Rahangdale et al.14 in the current issue of Anesthesia & Analgesia compares IV versus perineural dexamethasone (8 mg dosage used in each treatment), versus saline control. Specifically, postoperative analgesia after foot-ankle surgery is addressed. In this editorial, we will describe 2 specific major concerns regarding the methodology and outcome of this study. First, we will address a potentially important safety issue9 with respect to perineural dexamethasone, which was both cited by Rahangdale et al., 14 and published before Rahangdale et al. 14 enrolled patients for the present study. Then, we will address how the absence of dexamethasone in the saphenous nerve block treatment protocol for perineural dexamethasone patients, an anatomic limitation that the authors openly acknowledged, potentially invalidates the finding of this investigation. The net effects of this investigation are that we now have further basis to eliminate future study of perineural dexamethasone at dosages 8 mg or greater (if not ≥4 mg), and fundamentals in the anatomy of perineural analgesia should be fully acknowledged when perineural pharmacology strategies are being compared.