Pathophysiology
Clinical meaning
Sepsis is life-threatening organ dysfunction caused by a dysregulated host response to infection. The Sepsis-3 definition uses SOFA score: increase ≥2 points indicates sepsis. Quick SOFA (qSOFA) bedside screening uses three criteria (1 point each): RR ≥22, altered mental status (GCS <15), SBP ≤100 — score ≥2 prompts further assessment. Pathophysiology involves pathogen-associated molecular patterns activating immune cells via toll-like receptors, triggering cytokine storm (TNF-alpha, IL-1, IL-6) causing widespread endothelial dysfunction, vasodilation, capillary leak, microvascular thrombosis, and multi-organ failure. Septic shock is sepsis with persistent hypotension requiring vasopressors for MAP ≥65 AND lactate >2 mmol/L despite adequate fluid resuscitation. The Hour-1 Bundle (cultures, antibiotics, IV fluids, lactate, vasopressors) saves lives.