Lung mechanics and histology during sevoflurane anesthesia in a model of chronic allergic asthma

BACKGROUND: There are no studies examining the effects of sevoflurane on a chronically inflamed and remodeled airway, such as that found in asthma. In the present study, we sought to define the respiratory effects of sevoflurane in a model of chronic allergic asthma. For this purpose, pulmonary mechanics were studied and lung morphometry analyzed to determine whether the physiological modifications reflected underlying morphological changes. METHODS: Thirty-six BALB/c mice (20-25 g) were randomly divided into four groups. In OVA groups, mice were sensitized with ovalbumin and exposed to repeated ovalbumin challenges. In SAL groups, mice received saline using the same protocol. Twenty-four hours after the last challenge, the animals were anesthetized with pentobarbital sodium (PENTO, 20 mg/kg i.p.) or sevoflurane (SEVO, 1 MAC). Lung static elastance (E-st), resistive (Delta P-1) and viscoelastic/inhomogeneous (Delta P-2) pressure decreases were analyzed by an end-inflation occlusion method. Lungs were fixed and stained for histological analysis. RESULTS: Animals in the OVASEVO group showed lower Delta P-1 (38%), Delta P-2 (24%), and E-st (22%) than animals in the OVAPENTO group. Histology demonstrated greater airway dilation (16%) and a lower degree of alveolar collapse (25%) in the OVASEVO compared with OVAPENTO group. Delta P-1 was lower (35%) and airway diameters larger (12%) in the SALSEVO compared with SALPENTO group. CONCLUSION: Sevoflurane anesthesia acted both at airway level and lung periphery reducing (Delta P-1 and Delta P-2 pressures, and E-st in chronic allergic asthma.