Clinical meaning
Septic shock is the most severe manifestation of sepsis, defined as sepsis with persistent hypotension requiring vasopressors to maintain MAP ≥ 65 mmHg and serum lactate > 2 mmol/L despite adequate fluid resuscitation. The pathophysiology involves a dysregulated host immune response to infection triggering massive cytokine release (cytokine storm) leading to widespread vasodilation, increased capillary permeability, and myocardial depression. Endotoxins from gram-negative bacteria and exotoxins from gram-positive organisms activate the inflammatory cascade including complement, coagulation, and fibrinolytic systems. Microvascular thrombosis impairs tissue oxygen delivery despite adequate cardiac output, leading to cellular hypoxia and lactate accumulation. Organ dysfunction progresses from reversible to irreversible, affecting kidneys (oliguria), lungs (ARDS), liver (coagulopathy), and brain (altered mental status). The Surviving Sepsis Campaign emphasizes the 1-hour bundle: blood cultures, broad-spectrum antibiotics, lactate measurement, and fluid resuscitation.
Exam relevance
Risk factors: - Active infection (pneumonia, UTI, intra-abdominal, skin/soft tissue) - Immunocompromised state (chemotherapy, HIV, corticosteroids, organ transplant) - Extremes of age (neonates and elderly > 65 years) - Invasive devices (central lines, urinary catheters, mechanical ventilation) - Chronic diseases (diabetes, cirrhosis, chronic kidney disease)