What is the definition of sepsis?

Definition of Sepsis

Sepsis is defined as life-threatening organ dysfunction caused by a dysregulated host response to infection, with organ dysfunction represented by an increase in the Sequential Organ Failure Assessment (SOFA) score of 2 points or more. 1

Current Definition Framework (Sepsis-3)

• The current definition of sepsis was established in 2016 (Sepsis-3) by the Society of Critical Care Medicine and the European Society of Intensive Care Medicine, replacing previous definitions that focused on systemic inflammatory response syndrome (SIRS) 2
• Organ dysfunction can be identified clinically by an increase in the SOFA score of ≥2 points, which is associated with in-hospital mortality >10% 1
• The previous concepts of SIRS and "severe sepsis" are no longer used in the current definition framework 1

Quick SOFA (qSOFA) Criteria

• qSOFA consists of three clinical variables for rapid identification of patients at risk of sepsis outside the ICU setting 1:
  • Respiratory rate ≥22 breaths/min
  • Altered mental status (Glasgow Coma Scale score ≤13)
  • Systolic blood pressure ≤100 mmHg
• Presence of at least 2 of these criteria suggests higher risk of poor outcomes typical of sepsis 1

Evolution of Sepsis Definitions

• Previous definitions (pre-2016) focused heavily on inflammation and used SIRS criteria 1:
  • Temperature >38°C or <36°C
  • Heart rate >90 beats/minute
  • Respiratory rate >20 breaths/minute or PaCO2 <32 mmHg
  • White blood cell count >12,000/mm³ or <4,000/mm³, or >10% immature (band) forms
• The 1991 consensus defined sepsis as SIRS triggered by infection 3
• The 2001 revision incorporated threshold values for organ damage 3
• The 2016 Sepsis-3 definition eliminated SIRS criteria and shifted focus to organ dysfunction 3

Septic Shock Definition

• Septic shock is defined as a subset of sepsis with particularly profound circulatory, cellular, and metabolic abnormalities associated with a greater risk of mortality 1, 4
• Clinically identified by 4, 5:
  • Vasopressor requirement to maintain mean arterial pressure ≥65 mmHg
  • Serum lactate level >2 mmol/L (>18 mg/dL) despite adequate volume resuscitation
• Septic shock represents the most severe form on the sepsis spectrum 5

Pathophysiology of Sepsis

• Sepsis involves a dysregulated inflammatory response that can lead to multi-organ failure 1
• The pathophysiology includes 4, 5:
  • Profound circulatory dysfunction with vasodilation and increased vascular permeability
  • Microcirculatory dysfunction leading to tissue hypoperfusion
  • Cellular and metabolic abnormalities including altered cellular metabolism leading to lactate accumulation

Clinical Implications

• Early recognition is crucial for improving outcomes 1, 5
• Patient factors including age and comorbidities significantly affect the course of sepsis 1
• Special considerations include 1:
  • Immunocompromised patients have increased susceptibility to sepsis due to pre-existing immune system dysfunction
  • Elderly patients may present with attenuated inflammatory responses despite severe infection

Common Pitfalls in Identifying Sepsis and Septic Shock

• Failing to recognize perfusion abnormalities despite normal blood pressure in patients receiving vasopressors 4
• Delaying vasopressor initiation while continuing excessive fluid administration 4
• Not measuring lactate levels, which are essential for diagnosis according to current definitions 4
• Confusing septic shock with other forms of distributive shock 4