Systemic Inflammatory Response During Coronary Artery Bypass Grafting with Cardiopulmonary Bypass: Cellular and Molecular Mechanisms

Coronary artery bypass grafting (CABG) utilizing cardiopulmonary bypass (CPB) remains a cornerstone of treatment for advanced multivessel coronary artery disease. During the ischemic period, myocardial cells become injured and increasingly depend on anaerobic metabolism. After reperfusion, exposure of blood components to artificial surfaces, combined with ischemia–reperfusion injury, surgical trauma, and gut translocation of endotoxins, triggers a complex systemic inflammatory response syndrome (SIRS). This inflammatory cascade involves a tightly regulated network of humoral cascades (complement, contact, coagulation, and fibrinolytic systems) and cellular effectors (neutrophils, monocytes, endothelial cells, and platelets). Molecular signaling pathways, notably Toll-like receptor 4 (TLR4) activation, nuclear factor kappa B (NF-κB) nuclear translocation, mitogen-activated protein kinase (MAPK) phosphorylation, and NLRP3 inflammasome assembly, drive a cytokine storm characterized by massive releases of interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-8 (IL-8). These molecular events lead to endothelial barrier disruption, vasoplegic shock, acute lung injury, myocardial dysfunction, and acute kidney injury. This comprehensive narrative review provides a detailed synthesis of the cellular and molecular mechanisms underlying CPB-induced SIRS, highlights recent advances in neutrophil extracellular trap (NET) dynamics and microvascular injury, and evaluates contemporary pharmacological and bioengineering therapeutic strategies designed to mitigate postoperative organ dysfunction.