Which of the following defines septic shock: A. Sepsis + organ dysfunction, B. Systemic Inflammatory Response Syndrome (SIRS) + infection, C. Severe sepsis + hypotension, D. Tachycardia + leukocytosis?

Definition of Septic Shock

Septic shock is defined as severe sepsis plus hypotension persisting despite adequate fluid resuscitation. 1

Understanding the Sepsis Spectrum

Based on the most recent guidelines, the progression of sepsis follows a clear pathway:

1. SIRS (Systemic Inflammatory Response Syndrome): Characterized by at least two of:

   • Temperature >38°C or <36°C
   • Heart rate >90 beats per minute
   • Respiratory rate >20 breaths per minute or PaCO2 <32 mmHg
   • White blood cell count >12,000/μL or <4,000/μL, or >10% immature forms 1

2. Sepsis: SIRS plus suspected or documented infection 1

3. Severe Sepsis: Sepsis plus organ dysfunction, hypotension, or hypoperfusion abnormalities 1

4. Septic Shock: Severe sepsis with hypotension that persists despite adequate fluid resuscitation 1

Clinical Criteria for Septic Shock

Septic shock is clinically identified by:

• Hypotension (systolic BP <90 mmHg or MAP <65 mmHg or a decrease in SBP >40 mmHg)
• Persisting despite adequate fluid resuscitation (typically 30 mL/kg crystalloid challenge)
• Requiring vasopressor therapy to maintain MAP ≥65 mmHg
• Associated with perfusion abnormalities such as lactic acidosis, oliguria, or altered mental status 1

Analyzing the Answer Options

A. Sepsis + organ dysfunction - This is the definition of severe sepsis, not septic shock 1

B. SIRS + infection - This is the definition of sepsis 1

C. Severe sepsis + hypotension - This correctly defines septic shock, as septic shock is severe sepsis (which already includes organ dysfunction) plus hypotension persisting despite adequate fluid resuscitation 1

D. Pulse >90 + WBCs >12000 - These are merely two SIRS criteria and do not constitute septic shock 1

Important Clinical Implications

Understanding the correct definition of septic shock is critical for:

1. Early Recognition: Mortality from septic shock ranges from 40-54%, significantly higher than sepsis (10-15%) or severe sepsis (17-20%) 2

2. Appropriate Management: Patients with septic shock require:

   • Immediate fluid resuscitation
   • Early vasopressor therapy
   • Source control of infection
   • Appropriate antibiotic therapy 1

3. Risk Stratification: The distinction between severe sepsis and septic shock stratifies patients into groups with different mortality risks 2

Evolving Definitions

It's worth noting that sepsis definitions have evolved. The 2016 Sepsis-3 consensus defines septic shock as:

• A subset of sepsis with profound circulatory, cellular, and metabolic abnormalities
• Clinically identified by vasopressor requirement to maintain MAP ≥65 mmHg AND serum lactate >2 mmol/L despite adequate fluid resuscitation 3, 4

However, the question is based on the traditional definition which remains widely used in clinical practice.