What is the new definition of sepsis?

New Definition of Sepsis (Sepsis-3)

Sepsis is now 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

Key Changes from Previous Definitions

The 2016 Sepsis-3 consensus fundamentally restructured how we conceptualize and diagnose sepsis 3:

• The term "severe sepsis" has been eliminated as redundant—all sepsis is now considered life-threatening by definition 1, 2
• SIRS criteria are no longer required for sepsis diagnosis, addressing the previous problem of excessive focus on inflammation and poor specificity 3, 4
• Organ dysfunction is now central to the definition rather than inflammatory markers alone 2, 5

Clinical Operationalization

SOFA Score Criteria

• An increase of ≥2 points in SOFA score from baseline identifies organ dysfunction associated with in-hospital mortality >10% 2, 3
• This represents a shift from inflammation-based criteria to dysfunction-based criteria 4

Quick SOFA (qSOFA) for Rapid Screening

For patients outside the ICU with suspected infection, use qSOFA to identify those at higher risk 2, 6:

• Respiratory rate ≥22 breaths/min
• Altered mental status (Glasgow Coma Scale ≤13)
• Systolic blood pressure ≤100 mmHg

Presence of ≥2 qSOFA criteria suggests higher risk of poor outcomes and warrants further evaluation with full SOFA scoring 2, 3

Septic Shock Definition

Septic shock is a subset of sepsis with particularly profound circulatory, cellular, and metabolic abnormalities carrying mortality rates >40% 1, 7

Clinical identification requires BOTH 2, 7, 3:

• Vasopressor requirement to maintain MAP ≥65 mmHg
• Serum lactate >2 mmol/L (>18 mg/dL) despite adequate fluid resuscitation

Critical Distinctions from Old Definitions

What Changed:

• Old (Sepsis-1/2): Required ≥2 SIRS criteria (temperature >38°C or <36°C, HR >90, RR >20, WBC >12,000 or <4,000) plus infection 2, 4
• New (Sepsis-3): Requires infection PLUS organ dysfunction (SOFA ≥2), regardless of SIRS 1, 2

Why It Matters:

• SIRS criteria had poor specificity—present in many hospitalized patients without sepsis 3, 4
• The new definition better identifies patients at risk of death, with SOFA ≥2 associated with >10% mortality 2, 3
• Eliminates the misleading concept that sepsis follows a linear continuum through "severe sepsis" to shock 3

Common Pitfalls to Avoid

• Do not wait for SIRS criteria before considering sepsis—they are no longer part of the definition 2, 4
• Do not use qSOFA as a diagnostic criterion—it is a screening tool for identifying at-risk patients who need full SOFA assessment 6
• Do not assume normal blood pressure excludes septic shock—patients on vasopressors may still have perfusion abnormalities despite MAP ≥65 mmHg 7
• Recognize that elderly and immunocompromised patients may present with attenuated inflammatory responses despite severe organ dysfunction 2, 7

Clinical Implementation

The pathophysiology involves dysregulated inflammatory response leading to multi-organ failure, not simply excessive inflammation 2, 5. This distinction is crucial: the host response in sepsis may represent an adaptive effort to a hostile environment rather than purely harmful dysregulation 8.

Early recognition using these updated criteria is essential for improving outcomes, as sepsis management in the initial hours significantly impacts mortality 1, 9.