Definition of Sepsis According to Current Guidelines
Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, operationalized by an acute increase in the Sequential Organ Failure Assessment (SOFA) score of 2 points or more. 1, 2, 3
Core Sepsis-3 Definition (Current Standard)
The Society of Critical Care Medicine and European Society of Intensive Care Medicine established the Sepsis-3 definition in 2016, which fundamentally shifted the conceptual framework away from inflammation-focused criteria: 3
- Sepsis requires two components: documented or suspected infection PLUS organ dysfunction (≥2 point increase in SOFA score) 1, 2
- A SOFA score increase of ≥2 points correlates with in-hospital mortality >10%, providing clinical significance to the threshold 1, 3
- The terms "severe sepsis" and "SIRS-based sepsis" are obsolete and should no longer be used 1, 2, 3
Septic Shock Definition
Septic shock represents a subset of sepsis with particularly profound abnormalities and requires BOTH of the following criteria: 1, 2, 3
- Vasopressor requirement to maintain mean arterial pressure (MAP) ≥65 mmHg 1, 2
- Serum lactate >2 mmol/L (>18 mg/dL) despite adequate fluid resuscitation 1, 2, 3
- This combination is associated with hospital mortality rates >40% 3
Quick SOFA (qSOFA) for Rapid Screening
For rapid bedside identification of at-risk patients outside the ICU, qSOFA consists of three simple clinical variables (1 point each): 1, 4, 3
- Respiratory rate ≥22 breaths/min 1, 3
- Altered mental status (Glasgow Coma Scale ≤13) 1, 3
- Systolic blood pressure ≤100 mmHg 1, 4, 3
A qSOFA score ≥2 indicates higher risk of poor outcomes and should prompt full SOFA score calculation. 1, 3 Note that qSOFA uses a systolic BP threshold of ≤100 mmHg (not the traditional <90 mmHg for hypotension), allowing earlier identification of at-risk patients. 4
SOFA Score Components
The full SOFA score assesses six organ systems (0-4 points each): 2
Respiratory: PaO₂/FiO₂ ratio from <400 (1 point) to <100 with mechanical ventilation (4 points) 2
Cardiovascular: MAP <70 mmHg (1 point) escalating to high-dose vasopressors—dopamine >15 OR epinephrine >0.1 OR norepinephrine >0.1 mcg/kg/min (4 points) 2
Hepatic: Bilirubin 1.2-1.9 mg/dL (1 point) to >12.0 mg/dL (4 points) 5
Coagulation: Platelets <150,000/μL (1 point) to <20,000/μL (4 points) 5
Renal: Creatinine 1.2-1.9 mg/dL (1 point) to >5.0 mg/dL or urine output <200 mL/day (4 points) 5
Neurological: Glasgow Coma Scale 13-14 (1 point) to <6 (4 points) 5
Evolution from Previous Definitions
The Sepsis-2 definition (2001) required proven or suspected infection plus ≥2 SIRS criteria: 5
- Heart rate >90 bpm 5
- Respiratory rate ≥20/min or PaCO₂ <32 mmHg 5
- Temperature <36°C or >38°C 5
- White blood cell count <4,000 or >12,000/mm³ or >10% immature forms 5
This SIRS-based approach was abandoned because it lacked specificity, had excessive focus on inflammation, and perpetuated the misleading concept that sepsis follows a continuum through "severe sepsis" to shock. 3, 6
Critical Clinical Caveats
The qSOFA score has limited sensitivity (31-36% for ICU admission, 60-68% for 48-hour mortality) in prehospital and emergency department settings, meaning it should be used as a screening tool to prompt further evaluation, not as a definitive diagnostic criterion. 7 When qSOFA is negative but clinical suspicion remains high, proceed with full SOFA assessment. 1
Early recognition remains paramount despite definitional changes—the requirement for organ dysfunction in the Sepsis-3 definition should not delay intervention in patients with suspected infection and clinical deterioration. 5