SIRS (Systemic Inflammatory Response Syndrome) is defined as ≥2 of the 4 criteria below. When SIRS is present with a confirmed or suspected infection, the patient meets criteria for Sepsis (Sepsis-2 definition). Note: Sepsis-3 (Singer 2016) replaces SIRS with SOFA ≥2, but the SIRS/Sepsis-2 framework remains widely used in many settings including the Philippines.
SIRS criteria (≥2 required):
- Temperature >38°C or <36°C
- Heart rate >90 bpm
- Respiratory rate >20/min OR PaCO₂ <32 mmHg
- WBC >12,000/µL or <4,000/µL OR >10% bands
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When to Use
Appropriate uses
- Screening for sepsis in emergency, ward, or ICU patients
- AKI workup — sepsis is the most common cause of AKI in hospitalized patients
- Triage for antibiotic escalation and fluid resuscitation
Pearls & Pitfalls
Key pearls
- SIRS criteria alone are non-specific — can be met with trauma, burns, pancreatitis, post-surgery
- Sepsis-3 (SOFA ≥2) has higher specificity but requires lab data
- qSOFA (RR ≥22, altered mentation, SBP ≤100) is a rapid bedside screen
- Septic shock = sepsis + vasopressor requirement + lactate >2 mmol/L despite adequate fluid
- CKD/dialysis patients may have blunted febrile response — WBC/respiratory criteria gain importance
Why Use It
Rapid standardized classification for triage and antibiotic timing
Every hour delay in antibiotics increases sepsis mortality. The SIRS/Sepsis-2 framework provides a rapid, standardized classification that can be applied at the bedside with minimal equipment, supporting early recognition and escalation.
SIRS Criteria (check all that apply)
Check each criterion that is present. The classification updates automatically as you check items.
SIRS Criteria
Infection Status
Organ Dysfunction (Severe Sepsis — check any present):
Septic Shock (informational — not a checkbox)
Septic Shock = Sepsis + vasopressor requirement despite adequate fluids + lactate >2 mmol/L (Sepsis-3 definition). Requires vasopressor therapy to maintain MAP ≥65 mmHg.
Next Steps
Use the classification to guide immediate management:
- SIRS from suspected infection: Blood cultures × 2 before antibiotics, IV broad-spectrum antibiotics within 1 hour, 30 mL/kg IV crystalloid bolus if hypotensive or lactate ≥2.
- Severe Sepsis / organ dysfunction: ICU consult, repeat lactate at 2 hours, organ-specific support.
- Septic Shock: Vasopressors (norepinephrine first-line), target MAP ≥65 mmHg; consider hydrocortisone if refractory.
- SIRS without infection: Evaluate for non-infectious cause (trauma, pancreatitis, burns, post-surgery). Treat underlying condition; if infection later confirmed, escalate antibiotics promptly.
Evidence & References
References
- Bone RC, Balk RA, Cerra FB, et al. Definitions for sepsis and organ failure and guidelines for the use of innovative therapies in sepsis. Chest. 1992;101(6):1644–1655. (Sepsis-2)
- 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.
- 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.
