NMBAs and anaphylaxis

Although neuromuscular blocking agents (NMBAs) are associated with a few allergic reactions, they form an important component of anaesthesia. Their role is pivotal in facilitating muscle relaxation for intubation and for perfect surgical conditions. Hence, NMBAs are virtually indispensable if a perfect anaesthetic has to be administered. Avoiding a muscle relaxant does have its down side, in terms of a higher incidence of laryngo-pharyngeal trauma. A study that looked at induction using a propofol/alfentanyl combination with/out rocuronium resulted in the rocuronium group scoring higher in terms of ease of intubation, haemodynamic conditions and post-intubation symptoms.

A French retrospective study looked at 518 cases in which an anaphylactic reaction was encountered during anaesthesia. Of these cases, 58% (306 cases) of the reactions were caused by NMBAs, with rocuronium being associated with 132 reactions. The rate of incidence of anaphylactic reactions reported from most studies is approximately 1 in 15,000.

The quaternary ammonium group, a key molecule of all NMBAs, is the main antigenic determinant. It has the capability of inducing an allergic reaction by bridging the IgE antibodies. The flexible molecules in succinylcholine appear to be responsible for its higher allergenic potential when compared with non-depolarising muscle relaxants. The quaternary ammonium group is also present in many consumer products like soaps, perfumes and foodstuffs.