Respiratory Mechanics During Sevoflurane Anesthesia in Children With and Without Asthma

Anesthetic considerations in children with asthma

Due to the high prevalence of asthma and general airway reactivity, anesthesiologists frequently encounter children with asthma or asthma-like symptoms. This review focuses on the epidemiology, the underlying pathophysiology, and perioperative management of children with airway reactivity, including controlled and uncontrolled asthma. It spans from preoperative optimization to optimized intraoperative management, airway management, and ventilation strategies. There are three leading causes for bronchospasm (1) mechanical (eg, airway manipulation), (2) non-immunological anaphylaxis (anaphylactoid reaction), and (3) immunological anaphylaxis. Children with increased airway reactivity may benefit from a premedication with beta-2 agonists, non-invasive airway management, and deep removal of airway devices. While desflurane should be avoided in pediatric anesthesia due to an increased risk of bronchospasm, other volatile agents are potent bronchodilators. Propofol is superior in blunting airway reflexes and, therefore, well suited for anesthesia induction in children with increased airway reactivity.

Modulation of neuronal nicotinic acetylcholine receptors by halothane in rat cortical neurons

Inhalational general anesthetics have recently been shown to inhibit neuronal nicotinic acetylcholine (ACh) receptors (nnAChRs) expressed in Xenopus laevis oocytes and in molluscan neurons. However, drug actions on these systems are not necessarily the same as those seen on native mammalian neurons. Thus, we analyzed the detailed mechanisms of action of halothane on nnAChRs using rat cortical neurons in long-term primary culture. Currents induced by applications of ACh via a U-tube system were recorded by the whole-cell, patch-clamp technique. ACh evoked two types of currents, alpha-bungarotoxin-sensitive, fast desensitizing (alpha 7-type) currents and alpha-bungarotoxin-insensitive, slowly desensitizing (alpha 4 beta 2-type) currents. Halothane suppressed alpha 4 beta 2-type currents more than alpha 7-type currents with IC(50) values of 105 and 552 microM, respectively. Halothane shifted the ACh dose-response curve for the alpha 4 beta 2-type currents in the direction of lower ACh concentrations and slowed its apparent rate of desensitization. The rate of recovery after washout from halothane block was much faster than the rate of recovery from ACh desensitization. Thus, the halothane block was not caused by receptor desensitization. Chlorisondamine, an irreversible open channel blocker for nnAChRs, caused a time-dependent block that was attenuated by halothane. These results could be accounted for by kinetic simulation based on a model in which halothane causes flickering block of open channels, as seen in muscle nAChRs. Halothane block of nnAChRs is deemed to play an important role in anesthesia via a direct action on the receptor and an indirect action to suppress transmitter release.