• Fabiano Di Marco, Daniele Bonacina, Emanuele Vassena, Erik Arisi, Anna Apostolo, Cristina Banfi, Stefano Centanni, Piergiuseppe Agostoni, and Roberto Fumagalli.
• From the *Pneumologia, Ospedale San Paolo, Dipartimento di Scienze della Salute, Università degli Studi di Milano, Milan, Italy; †Department of Experimental Medicine, University of Milano-Bicocca, Italy; ‡Centro Cardiologico Monzino IRCCS, Milano, Italy; §Centro Cardiologico Monzino IRCCS, Dipartimento di Scienze Cliniche e di Comunità, Sezione cardiovascolare, Università di Milano, Milan, Italy; ∥Division of Pulmonary and Critical Care and Medicine, Department of Medicine, University of Washington, Seattle, Washington; and ¶Anesthesia and Intensive Care, Ospedale Niguarda Ca' Granda, Milano, Italy.
• Anesth. Analg.. 2015 Feb 1;120(2):373-80.

BackgroundAn increased alveolar-arterial oxygen tension difference is frequent in anesthetized patients. In this study, we evaluated the effect on the lung of anesthesia, muscle paralysis, and a brief course of mechanical ventilation.MethodsLung diffusion for carbon monoxide (DLCO), including pulmonary capillary blood volume (Vc) and conductance of the alveolar-capillary membrane (DM), and pulmonary surfactant protein type B (a marker of alveolar damage) were measured in 45 patients without pulmonary disease undergoing extrathoracic surgery.ResultsAnesthesia, muscle paralysis, and mechanical ventilation led to impairment of gas exchange, with a reduction of DLCO values immediately after anesthetic induction due to a concomitant reduction of both DM and Vc. While changes in DM were due to the reduction of lung volume, changes in Vc were not limited to volume loss, since the Vc/alveolar volume ratio decreased significantly. Although DLCO and its components decreased immediately after induction, none of the values decreased further at 1 and 3 hours. Surfactant protein type B, however, was unchanged immediately after anesthesia but increased at 1 hour after induction and further increased after 3 hours of anesthesia. The level of alveolar damage correlated with the reduction of lung perfusion and lung dynamic strain (i.e., ratio between tidal volume and end-expiratory lung volume).ConclusionsA brief course of anesthesia and controlled ventilation leads to: (1) alveolar damage, which is correlated with lung strain and perfusion, and (2) impaired gas exchange mainly due to volume loss but also to reduced aerated lung perfusion.

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