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ANESTHETIC PHARMACOLOGY

The Involvement of Histaminic and Muscarinic Receptors in the Bronchoconstriction Induced by Myorelaxant Administration in Sensitized Rabbits

Walid Habre, MD, PhD^*, Ágnes Adamicza, PhD, Enikõ Lele, MD, Tímea Novák, Peter D. Sly, MBBS, MD, DSc, FRACP, and Ferenc Petak, MSc, PhD

From the *Pediatric Anesthesia Unit, Geneva Children's Hospital, Switzerland; Institute of Experimental Surgery, University of Szeged, Hungary; Department of Medical Informatics and Engineering, University of Szeged, Hungary; and Telethon Institute for Child Health Research and Centre for Child Health Research, University of Western Australia, Perth, Australia.

Address correspondence and reprint requests to Ferenc Petak, PhD, Department of Medical Informatics, University of Szeged, Koranyi fasor 9, H-6720 Szeged, Hungary. Address e-mail to petak{at}dmi.szote.u-szeged.hu.

BACKGROUND: Muscle relaxants cause bronchospasm via histamine release and/or by acting on the muscarinic receptors; we sought to characterize the respective importance of these pathways in the presence of bronchial hyperreactivity.

METHODS: Ovalbumin-sensitized rabbits were randomly assigned to several protocol groups: Group C comprised untreated animals; in the other three groups, either H1 and H2 histaminic receptor blockade was performed, leaving the M1, M2, and M3 muscarinic receptors functional (Group M123), or combining this treatment with M3 muscarinic receptor blockade (Group M12), or with vagotomy (Group M3). Respiratory system impedance was measured over a 90-s period, during which succinylcholine, mivacurium or atracurium was administered. To monitor the changes in lung mechanics, respiratory system impedance was averaged in a 2-s time window and fitted by a model featuring airway resistance and inertance and tissue damping and elastance.

RESULTS: The peak increases in airway resistance in Group C were greatest with succinylcholine (79 ± 17[SE]%) and mivacurium administration (75% ± 12%), whereas they were lower after attracurium (40% ± 11%). These changes were markedly attenuated by both histamine and muscarinic receptor blockade with the largest reduction in Group M3 for succinylcholine (14% ± 5.2%), and in Group M123 for mivacurium (5.1% ± 9.1%) and attracurium (7.8% ± 4.0%).

DISCUSSION: Although the bronchospasm developing in the allergic airways after muscle relaxants is mediated primarily by the histaminic pathway, the interactions of succinylcholine on the M1, M2, and M3 receptors, those of atracurium on the M1 and M2 receptors, and those of mivacurium on the M3 receptors may also play a role.