Defines systemic inflammatory response syndrome (SIRS), sepsis, severe sepsis, and septic shock based on clinical parameters. Provides the classic Sepsis-2 (2001) framework alongside the current Sepsis-3 (2016) definitions using SOFA/qSOFA for rapid bedside identification.

Parameters

SIRS Criteria (Sepsis-2: ≥2 of 4 required for SIRS)count

Temperature > 38.3°C (100.9°F) or < 36°C (96.8°F)Heart rate > 90 bpmRespiratory rate > 20 breaths/min OR PaCO2 < 32 mmHgWBC > 12,000/µL or < 4,000/µL or > 10% bands (immature neutrophils)

Sepsis (Sepsis-2: SIRS + suspected or confirmed infection source)any

Suspected or confirmed infection source (positive cultures, clinical infection site, or antimicrobial therapy initiated)

Organ Dysfunction Indicators (Sepsis-2 'Severe Sepsis' / Sepsis-3 Organ Dysfunction)any

Altered mental status (new confusion or reduced GCS from baseline)PaO2/FiO2 < 300 mmHg (or SpO2 <90% on room air without prior lung disease)Creatinine > 2.0 mg/dL or acute rise ≥ 0.5 mg/dL from baselineBilirubin > 2 mg/dL (hepatic dysfunction)Platelet count < 100,000/µL (thrombocytopenia)Lactate > 2 mmol/L (tissue hypoperfusion)Hypotension (SBP < 90 mmHg) that responds to IV fluids

Septic Shock Criteria (Sepsis-3: requires ALL three)any

Requires vasopressor to maintain MAP ≥ 65 mmHg DESPITE adequate fluid resuscitationSerum lactate > 2 mmol/L (despite adequate resuscitation)

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CalculatorsSIRS, Sepsis, and Septic Shock Criteria

Critical CareCriteria

SIRS, Sepsis, and Septic Shock Criteria