Pathophysiology
Clinical meaning
Critical care medicine manages life-threatening organ dysfunction requiring intensive monitoring and organ support. Shock represents inadequate tissue perfusion classified by etiology: distributive (septic -- most common ICU shock; vasodilatory from cytokine-mediated endothelial dysfunction), cardiogenic (pump failure from MI, cardiomyopathy, valve dysfunction), hypovolemic (hemorrhage, dehydration), and obstructive (PE, tension pneumothorax, cardiac tamponade). ARDS (acute respiratory distress syndrome) involves diffuse alveolar damage from pulmonary or extrapulmonary insults, causing non-cardiogenic pulmonary edema with bilateral infiltrates and refractory hypoxemia. Multi-organ dysfunction syndrome (MODS) is the progressive failure of two or more organ systems, driven by dysregulated inflammatory response, with mortality increasing by 15-20% per organ system involved.