Sepsis Criteria: SIRS, Sepsis-3, qSOFA, and What Changed in 2016
Sepsis definitions changed in 2016. Sepsis-3 retired SIRS as the diagnostic standard, but SIRS still appears on boards and in hospital protocols. Know both — and know why the change happened.
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Updated July 2026
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The 60-second version
Sepsis-3 (2016): organ dysfunction (SOFA ≥2) + suspected infection
SIRS (≥2 of): Temperature >38°C or <36°C, Heart rate >90 bpm, Respiratory rate >20 or PaCO2 <32, WBC >12,000 or <4,000 or >10% bands. SIRS + suspected infection = Sepsis (old definition). Sepsis + organ dysfunction = Severe sepsis. Severe sepsis + refractory hypotension = Septic shock.
Sepsis-3 (2016 Current Definition)
Sepsis = life-threatening organ dysfunction caused by a dysregulated host response to infection. Organ dysfunction is quantified by SOFA score increase ≥2. Septic shock = sepsis + vasopressor requirement to maintain MAP ≥65 mmHg + lactate >2 mmol/L despite adequate volume resuscitation. 'Severe sepsis' no longer exists as a term.
qSOFA — Bedside Screening Tool
Quick SOFA (qSOFA): 1 point each for: Altered mental status (GCS <15), Respiratory rate ≥22/min, Systolic BP ≤100 mmHg. Score ≥2 in a patient with suspected infection = high risk for sepsis — prompts full SOFA evaluation and escalation of care. Sensitivity ~50–70%; used for rapid bedside screening, not diagnosis.
Management Essentials (SEP-1 Bundle)
Hour-1 bundle: Measure lactate (remeasure if >2), obtain blood cultures before antibiotics, administer broad-spectrum antibiotics, 30 mL/kg IV crystalloid if hypotensive or lactate ≥4, apply vasopressors (norepinephrine first-line) if MAP <65 despite fluids. Mortality increases ~7% per hour of antibiotic delay in septic shock.
Test yourself
Quick check — 3 questions
1. A 68-year-old nursing home patient presents with temperature 38.8°C, HR 102, RR 24, and new confusion. BP 94/58. Urine culture is pending. Under Sepsis-3, what is the most likely diagnosis?
Explanation. Septic shock under Sepsis-3 requires: suspected infection + vasopressor needed to maintain MAP ≥65 + lactate >2 after adequate fluids. This patient likely meets septic shock criteria (hypotension needing vasopressors, new organ dysfunction). Culture results are not needed to diagnose sepsis — suspected infection suffices.
2. Which qSOFA criterion is NOT included in the score?
Explanation. qSOFA contains only three criteria: altered mental status, RR ≥22, and SBP ≤100. Temperature is a SIRS criterion but is NOT part of qSOFA — this is a common trap.
3. What is the first-line vasopressor in septic shock?
Explanation. Norepinephrine is the first-line vasopressor in septic shock per Surviving Sepsis Campaign guidelines. It reliably increases MAP via α1 vasoconstriction with less tachycardia than dopamine. Vasopressin is added second.
Frequently asked questions
Is SIRS still used to diagnose sepsis?
Not under Sepsis-3 (2016). SIRS was retired as a diagnostic criterion because it lacks specificity — patients without infection routinely meet SIRS criteria. Current diagnosis requires suspected infection plus evidence of organ dysfunction (SOFA score ≥2). However, SIRS still appears on older-format board exams and in some hospital protocols.
What is the first-line vasopressor in septic shock?
Norepinephrine (noradrenaline) is the first-line vasopressor for septic shock. It is an α1 > β1 agonist that increases SVR with modest cardiac effect. Vasopressin is added as a second agent to reduce norepinephrine requirements. Dopamine has fallen out of favor due to higher arrhythmia risk.
What lactate level indicates poor prognosis in sepsis?
Lactate >2 mmol/L indicates tissue hypoperfusion and is part of the septic shock definition. Lactate >4 mmol/L is associated with significantly higher mortality even in patients without frank hypotension — sometimes called 'cryptic shock.' Serial lactate clearance (≥10% reduction per 2 hours) is a resuscitation target.
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