Respiratory consequences of perioperative complications related to anaesthesia

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Abstract in foreign language

Aspiration of the gastric contents, blood loss and fluid replacement are important factors of perioperative morbidity. Respiratory effects are among the most critical changes related to their morbidity. In the present thesis, an animal model was established for the separate investigation of the mechanical properties of the left and the right lung. The use of a double-lumen ET tube allowed the independent introduction of the forcing signal to each lung, allowing characterization of the changes in the mechanical properties of each lung. We have demonstrated that the initial changes induced by bronchoaspiration are dominated by the direct effects, since the unaffected lung was not altered in terms of lung mechanics, and that the application of moderate PEEP is beneficial in the management of bronchoaspiration. We have also adapted a well-established animal model for the investigation of acute blood loss, but also improved it for the examination of the effects of various methods of fluid replacement. The sequential removal and replacement of blood mimicked continuous, but hidden surgical bleeding with its replacement. Our measurements did not reveal a difference between fluid replacement with colloid or crystalloid, represented in comparable oedema formation and adverse changes in the viscoelastic properties of the lung. These findings contribute to a better understanding of the underlying mechanisms of these anaesthesia-related complications through a description of the not yet characterized respiratory changes initiated by bronchoaspiration of the gastric contents and by acute blood loss and its fluid replacement. If it is assumed that the same mechanisms are present in humans, this better understanding might further improve the management of these adverse perioperative events and reduce their morbidities.

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