Table 1. A summary of the change in the definitions and approach to patients with suspected sepsis.

	Sepsis	Severe sepsis	Septic shock
Old Sepsis-2 Definitions (2001)	Infection + at least two systemic inflammatory response syndrome (SIRS) criteria SIRS criteria:         1.  Tachycardia (heart rate >90 beats per minute)         2.  Tachypnoea (respiratory rate >20 breaths per minute)         3.  Fever or hypothermia (temperature >38°C or <36°C)         4.  Leucocytosis (white cell count >12 g/L), leukopenia (white cell count <4 g/L) or bandemia (>10% immature neutrophils in blood)	Sepsis + evidence of organ dysfunction or tissue hypoperfusion or hypotension	Severe sepsis + refractory hypotension
Current Sepsis-3 Definitions (2016)	Infection + organ dysfunction Organ dysfunction defined as a sequential organ failure assessment (SOFA) score of at least 2 Alternatively, fulfilling at least two of the following quick SOFA criteria correlates with a high risk of mortality (>24%) and should prompt further investigation of organ dysfunction.         1.  Hypotension (systolic blood pressure <100 mm Hg)         2.  Altered mental status (Glasgow Coma Scale score <15)         3.  Tachypnoea (respiratory rate >22 breaths per minute)	Not applicable	Vasopressors required to maintain a mean arterial pressure of at least 65 mm Hg + serum lactate level of at least 2 mmol/L

The new guidelines have removed the term “severe sepsis” and require evidence of organ dysfunction in order for a patient to be classed as being septic.