Sepsis is defined as a systemic inflammatory response syndrome (SIRS) in the presence of proven or suspected infection.

SIRS is a combination of 2 or more of the following:

• Temperature >38°C or<36°C
• Heart rate >90 bpm
• Respiratory rate >20 or PaCo₂ <4.3 Kpa
• White cell count (WCC) >12,000/mm³ or <4,000/mm³

Septic shock is defined as sepsis with hypotension, which despite fluid resuscitation leads to organ dysfunction.