What is the definition of septic shock?

Definition of Septic Shock

Septic shock is defined as sepsis-induced hypotension persisting despite adequate fluid resuscitation, accompanied by evidence of tissue hypoperfusion. 1

Key Diagnostic Criteria

Septic shock can be clinically identified by the presence of:

1. Underlying sepsis: Life-threatening organ dysfunction caused by a dysregulated host response to infection 2

2. Persistent hypotension: Requiring vasopressors to maintain mean arterial pressure ≥65 mmHg 1

3. Evidence of hypoperfusion: Serum lactate level >2 mmol/L (>18 mg/dL) despite adequate fluid resuscitation 1, 2

Understanding the Sepsis Spectrum

The progression from sepsis to septic shock follows a hierarchical pattern with increasing mortality:

• Sepsis: Infection with systemic manifestations (mortality 10-15%) 3
• Severe sepsis: Sepsis plus organ dysfunction (mortality 17-20%) 3
• Septic shock: Sepsis with persistent hypotension despite fluid resuscitation (mortality 43-54%) 3

Hemodynamic Parameters in Septic Shock

Septic shock is characterized by specific hemodynamic abnormalities:

• Systolic blood pressure <90 mmHg or a decrease >40 mmHg from baseline 1
• Mean arterial pressure (MAP) <70 mmHg 1
• Diastolic arterial pressure (DAP): Low DAP correlates with severity of arteriolar vasodilation 4

Clinical Manifestations

Patients with septic shock typically present with:

• Hypotension unresponsive to fluid resuscitation
• Tachycardia and tachypnea
• Altered mental status
• Oliguria
• Metabolic acidosis
• Elevated lactate levels
• Prolonged capillary refill time 2

Management Implications

The definition of septic shock has critical implications for treatment:

• Fluid resuscitation: Initial crystalloid challenge of 30 mL/kg body weight 3
• Vasopressor therapy: Should be initiated if hypotension persists after fluid challenge, with norepinephrine as the first-line agent 1, 5
• Target MAP: Maintaining 65-70 mmHg is a good initial goal during hemodynamic support 1
• Avoid fluid overload: Particularly in patients with generalized peritonitis, as it may aggravate gut edema and increase intra-abdominal pressure 1

Common Pitfalls in Recognition and Management

• Delayed recognition: Failure to identify septic shock early increases mortality
• Inadequate fluid resuscitation: Initial fluid challenge is essential before vasopressor initiation
• Focusing solely on blood pressure: Without addressing tissue perfusion markers
• Fluid overload: Excessive fluid administration can worsen outcomes 2

Monitoring Parameters

Continuous monitoring should include:

• Blood pressure (systolic, diastolic, and mean)
• Heart rate
• Urine output
• Lactate levels
• Central venous oxygen saturation (when available)
• Signs of peripheral perfusion 2

The definition of septic shock provides a framework for prompt recognition and aggressive management, which are essential for improving outcomes in this life-threatening condition.