SIRS describes the host response to a critical illness of infectious or noninfectious cause, such as burns, trauma, and pancreatitis. More specific definitions are as follows:
Sepsis is SIRS resulting from a presumed or known site of infection.
Severe sepsis is sepsis with an acute associated organ failure.
Septic shock, a subset of severe sepsis, is defined as a persistently low mean arterial blood pressure despite adequate fluid resuscitation.
Refractory septic shock is a persistently low mean arterial blood pressure despite vasopressor therapy and adequate fluid resuscitation.1
SIRS can be readily diagnosed at the bedside by the presence of at least two of the following four signs: body temperature alterations (hyperthermia or hypothermia), tachycardia, tachypnea, and changes in white blood cell count (leukocytosis or leukopenia).