Melbourne Veterinary School - Theses

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    Inflammation and endothelial perturbation in canine abdominal surgery: the potential modulatory effect of lidocaine
    Donaldson, Liam Robert ( 2019)
    Complication rates following emergency laparotomy surgery are high, with organ dysfunction being a commonly encountered post-operative complication. Given the endothelium acts as the interface between the systemic circulation and the organs, its function is vital to maintaining organ health. The endothelium is in a constant state of flux, impacted largely by the local environment of which it is a part. In the presence of wide-spread systemic inflammation, inflammatory mediators precipitate change to the structure of the endothelial glycocalyx. These changes result in shedding of the endothelial glycocalyx and alteration of the endothelial phenotype. The endothelium may, as a result, lose the capacity to regulate vasomotor tone, and shift toward a pro-inflammatory and pro-coagulant state. This predisposes to reduced tissue oxygen delivery, and organ dysfunction may ensue. This thesis aimed to answer two key questions: does surgical trauma induced in canine patients undergoing emergent abdominal surgery invoke a systemic inflammatory response and subsequent endothelial activation? And if so, does lidocaine, a proposed immunomodulatory drug, mitigate this effect when given in the post-operative period? Chapter two provides a detailed review of endothelial structure and function, and current literature pertaining to systemic inflammation and endothelial activation in the context of abdominal surgery. Chapter two also examines the literature regarding the proposed mechanisms through which lidocaine acts as an immunomodulatory drug, and reviews publications that investigate the use of lidocaine as an anti-inflammatory drug in human patients after abdominal surgery. Chapter three is a randomized, blinded clinical trial quantifying the effect of emergency abdominal surgery on the concentration of markers of systemic inflammation and endothelial perturbation in canine patients in the post-operative period. The trial also assessed the potential use of lidocaine as a post-operative immunomodulatory therapy in dogs having undergone laparotomy. Fifty canine patients undergoing abdominal surgery were enrolled in the study. Patients were randomized into two separate groups: a study group receiving lidocaine intravenously, and a control group receiving 0.9% NaCl intravenously for a twelve-hour period following abdominal surgery. Blood samples were gathered prior to surgery, followed by six and twelve hours post-operatively. Concentrations of markers of systemic inflammation (IL-6) and markers of endothelial perturbation (VEGF and HA) were quantified via means of ELISA at each time point. Results revealed a significant increase in the concentration of markers of systemic inflammation and endothelial perturbation in post-operative blood samples. No immunomodulatory or endothelial preserving effect of lidocaine was appreciated.