Table 1 Definitions used to select patients with severe sepsis at the ICU

SIRS criteria

At least two of the following within the first 24 hours of the ICU stay:

Core temperature > 38.0°C or < 36.0°C

Heart rate > 90 beats/min

Respiratory rate = 20 breaths/minute or PaCO₂ = 32 mmHg or mechanical ventilation

Leucocyte count < 4,000/mm³ or > 12,000/mm³

Infection

Diagnosis of infection confirmed by laboratory results within first 24 hours of ICU stay^a

Organ

At least one of the following to be present within the first 24 hrs of ICU stay:

dysfunction

Cardiovascular: systolic blood pressure = 90 mmHg or decrease in systolic blood pressure of = 40 mmHg, or use of vasoactive medication to maintain the blood pressure > 90 mmHg for = 1 hour

Renal: mean urine production < 0.50 ml/kg body weight per hour; if the patient is on chronic renal replacement therapy, then another organ failure dysfunction criterion must be satisfied

Respiratory: PaO₂/FiO₂ = 300 (or PaO₂/FiO₂ = 200 if admission diagnosis is respiratory infection)

Haematological: platelet count = 100,000/mm³

Metabolic: pH = 7.30