In the 1991 consensus conference, sepsis was defined as evidence of infection and the clinical picture of the systemic inflammatory
response syndrome (SIRS; i.e. two of the following clinical criteria: tachycardia, tachypnea, fever or hypothermia, and leukocytosis
or leukopenia). Severe sepsis is sepsis with evidence of organ dysfunction and hypotension or hypoperfusion. Septic shock
is severe sepsis with refractory hypotension.
Due to lack of specificity, the definition of SIRS leaves much to be desired in both human and veterinary applications. In
published SIRS criteria recommended for dogs, the sensitivity ranges from 77-97%, while the specificity is between 64 and
77%, no such study has been performed in cats. It is clear from the table below that almost any patient that comes into the
Emergency Room will fulfill at least 2 of criteria.
In 2001, there was a second (human) consensus conference, which expanded the criteria for SIRS by recommending the inclusion
of physical parameters and biomarkers (the term recently coined to describe measurable factors in blood or biological samples
that can be used to identify or stage disease). Many of the parameters and some of these biomarkers may also prove useful
in veterinary species. This newer approach, designated as PIRO, incorporates 4 factors in the stratification. The first factor
is Predisposition. Although many factors can influence "susceptibility", an area of active research in humans involves predisposing
genetic factors. While it has long been recognized that certain breeds or families of people may be more susceptible to diseases
individual genetic variations or polymorphisms appear to further contribute to susceptibility. Other predisposing factors
may be age, concurrent conditions and gender. The second factor is Infection. Clinically, we recognize that certain bacteria,
location of infection, or extent of infection, contribute to the risk of developing sepsis or septic shock. The third factor
is the host Response. Our current inability to readily identify and monitor biomarkers is the biggest limitation for this
component of the stratification scheme. However if we can determine whether the cat is in an excessively pro-inflammatory
state versus immune paralysis, or if there is evidence of adrenal or coagulation dysfunction, we will be better able to chose
appropriate and directed interventions. The fourth and final factor is Organ Dysfunction. Even more in cats than in people,
the extent of organ dysfunction will negatively influence outcome.
There does not seem to be either a breed or sex predilection for sepsis in cats. Cats with pyothorax were more likely to
come from multi-cat households and had a tendency to have a higher incidence of outdoor access. In one study of septic peritonitis,
male cats outnumbered female cats. Unlike dogs and humans in which diabetes is reported as a predisposing factor for hepatic
abscesses, no such predisposition has been reported in cats.