Anaphylaxis to neuromuscular-blocking drugs: all neuromuscular-blocking drugs are not the same.

5 January 2015 I n the current issue of Anesthesiology, Reddy et al.1 report a two-hospital, retrospective, observational, cohort study confirming that anaphylaxis is more common with rocuronium and succinylcholine than with atracurium, a topic that is difficult to assess and was first highlighted in this journal in 2003.2 Although any medication can potentially cause perioperative anaphylaxis, neuromuscular-blocking drugs (nMBDs), antibiotics, latex, and chlorhexidine are the most likely to do so. Regional differences regarding the relative risk of allergic reactions to nMBDs do exist. nMBDs represent the dominant causes of anaphylaxis in several countries and regions such as France,2–4 norway,5 spain,6 and Australasia,7 whereas other agents may be primarily involved in other countries.8 nevertheless, allergic reactions to nMBDs remain a serious concern for anesthesiologists because death may occur even when reactions are rapidly and adequately treated.9 The reported incidence of perioperative anaphylaxis is quite varying, ranging between 1:3,500 and 1:20,000. Part of the variability is likely due to difficulty in determining the exact exposures to the numerous drugs, blood products, and agents used in the operative setting. The number of documented cases of intraoperative anaphylaxis is typically reported in aggregate for a large population, leaving the specifics of the total amount and type of medications the population was exposed to in question. in the study by Reddy et al., the authors take the advantage of their ability to retrieve detailed information concerning new patient exposure to each nMBD from electronic anesthetic records available in the two participating centers over 7 yr. This allowed a more precise estimate of the number of patients exposed as the denominator when calculating the relative risk of allergic reactions associated with the use of each nMBD. This method helps eliminate the primary concern with data based on drug sales, which have the potential to overestimate the exposure resulting in a potential underestimation of anaphylaxis rate. interestingly, the authors’ findings are similar to the estimates of allergic reactions to nMBDs based on drug sales. This study confirms the increased relative risk of allergic reaction to succinylcholine and rocuronium in countries where a high rate of reaction to nMBDs is reported. The surveillance of intraoperative adverse drug reactions still represents a clinical and statistical challenge10 because these reactions are rare, random, and mostly independent from the repeated exposure of patients to anesthesia. in addition, possible biases and underreporting make comparison between drugs relatively difficult. Another weakness of any reporting system is that responsible physicians seem to have little understanding of which drug is actually causing the anaphylactic reaction when several drugs are simultaneously administered during anesthesia induction due to a lack of a single confirmatory test.11 With thorough review in this study, it was noted that 9 of the 21 cases of identified nMBD anaphylaxis did not meet the standard skin test criteria for positivity but correctly warranted inclusion based on clinical picture and adjunct testing. Because identification of the anaphylactic mechanism, of the responsible drug, and of the alternative safe agents is not always straightforward, a standard use of tryptase measurements in case of suspected allergic reactions and investigation of these reactions in compliance with established guidelines12 by allergists trained in the field of drug allergy working in close collaboration with anesthesiologists should be promoted.13,14 Reddy et al. confirm that Anaphylaxis to Neuromuscular-blocking Drugs