Systemic Inflammation Induced by Cardiopulmonary Bypass: A Review of Pathogenesis and Treatment

Abstract

The acute respiratory distress syndrome (ARDS) is a severe alteration in lung structure and function that develops secondary to a traumatic stimulus. When ARDS develops following cardiopulmonary bypass (CPB) it is know as postpump syndrome (PPS). ARDS can be caused by a single massive insult (“hit”); however, sequential minor insults (“hits”) are more common clinically. The concept of multiple sequential insults causing ARDS has been termed the “two-hit” model of ARDS. The purpose of this article is to summarize our studies testing the hypothesis that PPS is caused by multiple sequential insults. To confirm our hypothesis, we developed a porcine model of “two-hit” PPS. Our model was composed of sequential benign insults, with CPB as the “first hit” and low dose of endotoxin as the “second-hit.” It is our hypothesis that the mechanism of PPS is CPB-induced priming of polymorphonuclear leukocytes (PMNs) (“first-hit”) with subsequent PMN activation by a second insult (“second-hit”) such as endotoxin. Our model confirms this clinically relevant postulate, and we provide strategies to disrupt the inflammatory cascade leading to PPS.

Viruses in the Respiratory Tract in Elective Cardiac Surgery Patients

“…Notwithstanding the findings in our study, viral (re)activity is still likely to be one of the many factors contributing to the development of ARDS in patients following major surgery [9,11]. It is known that major surgery, transfusions and certain comorbidities (diabetes mellitus, cardiovascular disease, obesity and old age) are associated with dysregulation of innate and adaptive immunity, including impaired antigen presenting capacity, impaired production of pro-inflammatory mediators, inhibition of T-cell activity, dysregulation of cytokine production, disruption of Th1 and Th17 pathways, and increased apoptosis of immune cells [15].…”

“…prolonged mechanical ventilation time, Intensive Care Unit (ICU)-and hospital stay [2][3][4][5][6][7][8], and high mortality (50-90%) [4][5][6][7][8]. It is hypothesised that ARDS in these patients results from sequential events that lead to an inflammatory response with disruption of the alveolar wall (that comprises alveolar epithelial cells and capillary endothelial cells) and progressive alveolar oedema with disturbed gas exchange [9][10][11]. Endothelial injury by the systemic inflammatory response due to surgery itself, Cardiopulmonary Bypass [CPB] and blood transfusion [11], could be one of these factors, while the mode of mechanical ventilation [12], and collapse of the lung to facilitate the surgeon [13,14], could additionally also disrupt the epithelium of the alveolar wall.…”