Pathophysiology
Clinical meaning
Multiple Organ Dysfunction Syndrome (MODS) represents the progressive failure of two or more organ systems in acutely ill patients, most commonly triggered by sepsis, severe trauma, major burns, or pancreatitis. The pathophysiology follows a two-hit model: the initial insult activates the innate immune system, releasing damage-associated molecular patterns (DAMPs) and pathogen-associated molecular patterns (PAMPs). These activate inflammatory cascades through Toll-like receptors, triggering a cytokine storm (TNF-alpha, IL-1, IL-6, IL-8). The resulting systemic inflammatory response causes: (1) Endothelial dysfunction with widespread microvascular thrombosis, capillary leak, and tissue edema; (2) Mitochondrial dysfunction (cytopathic hypoxia) where cells cannot utilize oxygen; (3) Immune dysregulation with both hyperinflammation and immunoparalysis; (4) Microcirculatory failure with shunting of blood away from capillary beds. Organ failure progresses sequentially, typically affecting the lungs first (ARDS with PaO2/FiO2 ratio declining), then cardiovascular system (vasopressor-dependent hypotension), kidneys (oliguria, rising creatinine), liver (rising bilirubin, coagulopathy), hematologic system (thrombocytopenia, DIC), and finally the neurological system (encephalopathy). The Sequential Organ Failure Assessment (SOFA) score quantifies dysfunction across six organ systems: respiratory (PaO2/FiO2), coagulation (platelets), hepatic (bilirubin), cardiovascular (MAP/vasopressors), neurological (GCS), and renal (creatinine/urine output)....