Sepsis is systemic infection accompanied by a reaction that has been termed the systemic inflammatory response syndrome (SIRS). SIRS represents an acute inflammatory reaction with systemic manifestations caused by release into the bloodstream of numerous endogenous mediators of inflammation. SIRS can also be caused by acute pancreatitis and major trauma, including burns. It has previously been defined by 2 or more of the following:
- Temperature > 38° C or less than 35° C
- Heart rate > 90 beats/min
- Respiratory rate > 20 breaths/min or Paco2 less than 32 mmHg
- WBC count > 12,000 or less than 4,000 cells/μL or > 10% immature forms
Severe sepsis is sepsis accompanied by signs of failure of at least one organ. Cardiovascular failure is typically manifested by hypotension, respiratory failure by hypoxemia, renal failure by oliguria, and hematologic failure by coagulopathy.
Septic shock is severe sepsis with organ hypoperfusion and hypotension that are poorly responsive to initial fluid resuscitation.