≥2 SIRS criteria: consider sources of infection for sepsis
Sepsis = SIRS + suspected or present source of infection
Severe Sepsis = sepsis + (lactic acidosis, hypotension, or organ dysfunction)
Septic Shock = sepsis + hypotension refractory to adequate IV fluid resuscitation
Multiple Organ Dysfunction Syndrome = evidence of 2+ organs failing
American College of Chest Physicians/Society of Critical Care Medicine Consensus Conference: definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. Crit. Care Med. 20 (6): 864–74.