SIRS, Sepsis & Septic Shock Criteria Calculator

What are SIRS, Sepsis, and Septic Shock?

Systemic Inflammatory Response Syndrome (SIRS), sepsis, and septic shock represent a continuum of the body's response to infection or injury, with increasing severity and mortality risk. Early recognition and appropriate management are crucial for improving outcomes.

Clinical Definitions

SIRS (Systemic Inflammatory Response Syndrome)

SIRS is defined as the presence of two or more of the following criteria:

• Temperature >38°C (100.4°F) or <36°C (96.8°F)
• Heart rate >90 beats per minute
• Respiratory rate >20 breaths per minute or PaCO₂ <32 mmHg
• White blood cell count >12,000/mm³, <4,000/mm³, or >10% immature bands

Sepsis

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection. In clinical practice, organ dysfunction can be represented by an increase in the Sequential Organ Failure Assessment (SOFA) score of 2 points or more.

For rapid identification, the quick SOFA (qSOFA) criteria can be used, which includes:

• Respiratory rate ≥22 breaths per minute
• Altered mentation (Glasgow Coma Scale <15)
• Systolic blood pressure ≤100 mmHg

Septic Shock

Septic shock is a subset of sepsis with circulatory and cellular/metabolic dysfunction associated with a higher risk of mortality. It is clinically identified by:

• Requirement for vasopressors to maintain mean arterial pressure ≥65 mmHg
• Serum lactate level >2 mmol/L (18 mg/dL) despite adequate fluid resuscitation

Clinical Significance

Early recognition and treatment of sepsis significantly improve outcomes. The Surviving Sepsis Campaign guidelines recommend:

• Obtaining blood cultures before administering antibiotics
• Administering broad-spectrum antibiotics within 1 hour of recognition
• Rapid administration of 30 mL/kg crystalloid for hypotension or lactate ≥4 mmol/L
• Applying vasopressors if hypotension persists during or after fluid resuscitation

Limitations

The definitions and criteria for sepsis have evolved over time. The original SIRS criteria have limitations, including high sensitivity but low specificity. The newer Sepsis-3 definitions focus on organ dysfunction but may miss early sepsis. Clinical judgment remains essential in the diagnosis and management of sepsis.

References

1. Singer M, Deutschman CS, Seymour CW, et al. The Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016;315(8):801-810.
2. Rhodes A, Evans LE, Alhazzani W, et al. Surviving Sepsis Campaign: International Guidelines for Management of Sepsis and Septic Shock: 2016. Intensive Care Med. 2017;43(3):304-377.
3. Seymour CW, Liu VX, Iwashyna TJ, et al. Assessment of Clinical Criteria for Sepsis: For the Third International Consensus Definitions for Sepsis and Septic Shock (Sepsis-3). JAMA. 2016;315(8):762-774.