Stages of Septic Shock
Septic shock is not traditionally divided into distinct "stages" but rather represents the most severe point on a continuum of sepsis progression, following the sequence: infection → sepsis → severe sepsis → septic shock. 1
The Sepsis Continuum
The progression of systemic infection follows a well-established clinical framework that categorizes severity of illness:
1. Sepsis
- Defined as suspected or documented infection associated with signs of systemic inflammation 1
- Mortality ranges from 10-15% 2
2. Severe Sepsis
- Sepsis accompanied by organ dysfunction or tissue hypoperfusion 1
- Mortality ranges from 17-20% 2
- This represents a critical transition point where end-organ damage begins
3. Septic Shock
- The terminal point of this continuum, defined by sepsis-induced hypotension despite adequate fluid resuscitation 1
- Operationally identified by: vasopressor requirement to maintain mean arterial pressure ≥65 mmHg AND serum lactate >2 mmol/L (>18 mg/dL) in the absence of hypovolemia 3, 4
- Mortality exceeds 40% when both criteria are present 4
- Characterized by profound circulatory, cellular, and metabolic abnormalities 3, 4, 5
Clinical Recognition Framework
Rather than stages within septic shock itself, clinicians should recognize the hierarchical progression that leads to shock:
- Bacteremia → infection in the bloodstream without systemic signs 1
- Sepsis → systemic inflammatory response to infection 1
- Severe sepsis → organ dysfunction develops 1
- Septic shock → persistent hypotension requiring vasopressors plus elevated lactate 3, 4
Critical Pitfalls to Avoid
- Failing to recognize that septic shock is a clinical diagnosis, not a laboratory one - it requires both hemodynamic criteria (vasopressor need) and metabolic criteria (lactate >2 mmol/L) 3, 4
- Delaying vasopressor initiation while continuing excessive fluid administration - vasopressors should be started after 30 mL/kg crystalloid challenge if hypotension persists 4, 2
- Not measuring lactate levels - essential for diagnosis according to current definitions 3
- Confusing the continuum of sepsis progression with distinct "stages" of shock - this is a common conceptual error 1
Pathophysiological Characteristics
Once septic shock develops, it involves:
- Circulatory dysfunction: profound vasodilation and increased vascular permeability 3, 4
- Microcirculatory dysfunction: tissue hypoperfusion despite adequate blood pressure 3, 4
- Metabolic abnormalities: altered cellular metabolism leading to lactate accumulation 3, 4
- Immune dysregulation: both hyperinflammation and subsequent immunosuppression 5