A reply

Drs Jones and Turkstra raise an intriguing question: will the intravenous administration of sugammadex mitigate ongoing anaphylaxis due to rocuronium? If this strategy is to be effective, several criteria must be fulfilled. First, the anaphylactic reaction must be rocuronium-induced. This would appear to be self-evident, but the causative agent is incorrectly identified at the time of the reaction in approximately one-third of cases. Second, it would be necessary for the concentration of rocuronium at the effect site (tissue-bound mast cells and circulating basophils) to fall rapidly as a result of encapsulation by sugammadex. Third, it would be advantageous if the affinity of sugammadex for rocuronium exceeds the affinity of the complementary cell-bound IgE antibodies. Fourth, it would be necessary for the process of encapsulation to hide the epitope responsible for rocuronium-induced anaphylaxis. Fifth, it would be necessary for the relevant endogenous and exogenous steroids to be preserved in concentrations that would favour homeostasis. There are many uncertainties. It is not known which parts of the rocuronium molecule are responsible for antibody cross-linking [1], although it is known that substituted ammonium ions are central to the process. It is not certain whether the IgE antibodies form a homogeneous group: it is likely that more than one sensitising agent may be involved. The plasma half-life of the sugammadex-rocuronium complex exceeds that of the naked rocuronium molecule [2] and, if the allergenic determinant remains exposed despite the embracing sugammadex molecule, the allergenic determinant may persist in the circulation for longer than would otherwise be the case, with the attendant possibility of exacerbating the anaphylactic reaction. There is clearly much to be learned before sugammadex can be used in the management of rocuronium-induced anaphylaxis. In the meantime the 2009 Association of Anaesthetists of Great Britain and Ireland Safety Guidelines provide the most appropriate advice for managing anaphylaxis during anaesthesia [3].