SIRS: 2 or more of the following are present:

Heart rate > 90 beats per minute
Body temperature < 36 or > 38°C
Tachypnea (high respiratory rate) > 20 breaths per minute or, on blood gas, a PaCO2 < 4.3 kPa (32 mm Hg)
White blood cell count < 4000 cells/mm³ or > 12000 cells/mm³, or the presence of greater than 10% immature neutrophils.

SIRS+Infection=Sepsis

To diagnose septic shock the following two criteria must be met:

Evidence of infection, through a positive blood culture.
Refractory hypotension - hypotension despite adequate fluid resuscitation and cardiac output.

--In adults it is defined as a systolic blood pressure < 90 mmHg, or a MAP < 60 mmHg, without the requirement for inotropic support, or a reduction of 40 mmHg in the systolic blood pressure from baseline.

--In children it is BP < 2 SD of the normal blood pressure.

In addition to the two criteria above, two or more of the following must be present:

Tachypnea (high respiratory rate) > 20 breaths per minute or, on blood gas, a PaCO2 less than 32 mmHg.
White blood cell count < 4000 cells/mm³ or > 12000 cells/mm³.