What is Sepsis?  SIRS, Septic Shock...




What is meant by SIRS, sepsis and septic shock?

For many years doctors, attending intensive care units, used a variety of terms to describe illnesses associated with infection, or illness that looked like infection. These terms included sepsis, septicemia, bacteremia, infection, septic shock, toxic shock etc. Unfortunately there were two problems with these terms: 1. There were no strict definitions for the terms used, and often these words or phrases were used incorrectly. 2, An emerging body of evidence arose which led us to believe that systemic inflammation, rather than infection, was responsible for multi-organ failure. In the early 1990s a consensus conference between the ACCP and the SCCM laid out a new series of definitions for what is inflammation and what is sepsis (3). The terminology has come into common usage, albeit with some reservations (4;5) , and I recommend that you learn and use these definitions.


ACCP/SCCM Consensus Conference Definitions (3)

Please note that these definitions have recently been revised: the new definitions will be published in the summer of 2002.

A host response to the presence of micro-organisms or tissue invasion by microorganisms.


The presence of viable bacteria in circulating blood

Systemic Inflammatory Response Syndrome (SIRS)

The systemic inflammatory response to a wide variety of severe clinical insults, manifested by two or more of the following conditions:

  • Temperature > 38░C or < 36░C

  • Heart rate > 90 beats/min

  • Respiratory rate > 20 breaths/min or PaCO2 < 32 mm Hg

  • WBC count > 12,000/mm3 , < 4000/mm3 , or > 10% immature (band) forms.


The systemic inflammatory response to infection. In association with infection, manifestations of sepsis are the same as those previously defined for SIRS. It should be determined whether they are a direct systemic response to the presence of an infectious process and represent an acute alteration from baseline in the absence of other known causes for such abnormalities. The clinical manifestations would include two or more of the following conditions as a result of a documented infection:

Severe Sepsis/SIRS.

Sepsis (SIRS) associated with organ dysfunction, hypoperfusion, or hypotension. Hypoperfusion and perfusion abnormalities may include, but are not limited to, lactic acidosis, oliguria, or an acute alteration in mental status.

Refractory (Septic) Shock/SIRS Shock.

A subset of severe sepsis (SIRS) and defined as sepsis (SIRS) induced hypotension despite adequate fluid resuscitation along with the presence of perfusion abnormalities that may include, but are not limited to, lactic acidosis, oliguria, or an acute alteration in mental status. Patients receiving inotropic or vasopressor agents may no longer be hypotensive by the time they manifest hypoperfusion abnormalities or organ dysfunction, yet they would still be considered to have septic (SIRS) shock.

Multiple Organ Dysfunction Syndrome (MODS).

Presence of altered organ function in an acutely ill patient such that homeostasis cannot be maintained without intervention.








Please note: these tutorials are for personal study purposes only.  They are not currently peer reviewed, and no responsibility will be taken for mistakes or inaccuracies. Reproduction of information is forbidden. All material is copyrighted by the GasWorks Group.