Background: Volatile inhaled anesthetics exert a differential protective effect against bronchospasm development after cholinergic stimulation. However, their ability to inhibit the adverse respiratory consequences of an anaphylactic reaction after exposure to an allergen has not been characterized. We therefore compared the abilities of isoflurane, sevoflurane, and desflurane to prevent the lung constriction induced by an allergic reaction in a pediatric model of an anaphylactic reaction.
Methods: Low-frequency respiratory input impedance (Zrs) was measured in 4 groups of ovalbumin (OVA)-sensitized 5-week-old rabbit pups anesthetized with midazolam (group IV) and with inhaled isoflurane (group ISO), sevoflurane (group SEVO), or desflurane (group DES) at 1 minimum alveolar concentration. Zrs was measured under baseline conditions and after an anaphylactic lung response provoked by IV allergen injection (OVA 1 mg), during which the changes in airway resistance (Raw), tissue damping (G), and elastance obtained from Zrs were followed for 15 minutes.
Results: Allergen provocation generated immediate severe bronchoconstriction, with no statistically significant difference in Raw increase among the groups in the first 3 minutes. Conversely, the inhalation of volatile anesthetics accelerated the recovery from the allergen-induced bronchoconstriction, particularly in group SEVO where the Raw was significantly lower than that in group IV 4 minutes after the allergen challenge. These changes were paralleled by significant elevations in G in all groups, with a significantly more pronounced deterioration in the animals in group DES. The anesthetic regimen did not statistically significantly affect the sustained increases in elastance after OVA injections.
Conclusions: Our results reveal the lack of potential of the commonly used volatile anesthetics to inhibit the most severe acute phase of the constrictor response to allergen after anaphylaxis in both the central airway and peripheral lung compartments. Inhalation of volatile anesthetics, particularly sevoflurane, promotes an earlier easing of the bronchospasm; this beneficial profile may be advantageous in children with atopic lung diseases.