Lecture Notes: Different Types of Shock

Introduction

• Focus on two main high-yield points:
  1. Pathophysiology of shock
  2. Changes in cardiogenic parameters
• Five types of shock:
  1. Cardiogenic
  2. Hypovolemic
  3. Distributive (includes septic, neurogenic, anaphylactic)

Key Concepts

• Pathophysiology: Understand what leads from an underlying problem to shock.
• Cardiogenic Parameters: Key metrics include cardiac output, heart rate, systemic vascular resistance (SVR), oxygen saturation, pulmonary capillary wedge pressure.

Conceptualizing Shock

• Main problem in shock: Determines the type
  • Heart not working: Cardiogenic shock
  • Change in fluid status: Distributive shock
  • Low fluid levels: Hypovolemic shock
• Distributive shock includes:
  • Septic Shock
  • Neurogenic Shock
  • Anaphylactic Shock

Types of Shock

1. Cardiogenic Shock

• Cause: Heart problems (e.g., heart attack, cardiomyopathy, myocarditis, drugs)
• Pathophysiology:
  • Decreased cardiac output
  • Increased catecholamines (vasoconstriction)
  • Activation of RAS system (retention of sodium and fluid)
  • Shunting of blood to brain and vital organs
  • Leads to increased myocardial work and oxygen demand
• Up/Down Arrows:
  • Cardiac Output: ↓
  • Heart Rate: ↑
  • Central Venous Pressure: ↔/↑
  • Pulmonary Capillary Wedge Pressure: ↑
  • SVR: ↑
  • Oxygen Saturation: ↓

2. Hypovolemic Shock

• Cause: Loss of fluid
  • Hemorrhagic (blood loss, e.g., trauma, GI bleeds, postpartum hemorrhage)
  • Non-hemorrhagic (water loss, e.g., diarrhea, vomiting, burns)
• Pathophysiology:
  • Decreased intravascular volume
• Up/Down Arrows:
  • Cardiac Output: ↓
  • Heart Rate: ↑
  • Central Venous Pressure: ↔/↓
  • Pulmonary Capillary Wedge Pressure: ↓
  • SVR: ↑
  • Oxygen Saturation: ↓

3. Distributive Shock

• Types:
  • Septic Shock:
    • Abnormal response to infection
    • Massive vasodilation
  • Neurogenic Shock:
    • Loss of sympathetic tone (e.g., spinal injury)
    • Inability to vasoconstrict
  • Anaphylactic Shock:
    • Type 1 hypersensitivity reaction (IgE mediated)
    • Massive vasodilation
• Up/Down Arrows:
  • Septic Shock:
    • Cardiac Output: ↑
    • Heart Rate: ↑
    • Central Venous Pressure: ↔/↓
    • Pulmonary Capillary Wedge Pressure: ↓
    • SVR: ↓
    • Oxygen Saturation: ↑
  • Neurogenic Shock:
    • Cardiac Output: ↓
    • Heart Rate: ↓
    • Central Venous Pressure: ↔/↓
    • Pulmonary Capillary Wedge Pressure: ↓
    • SVR: ↓
    • Oxygen Saturation: ↓
  • Anaphylactic Shock:
    • Cardiac Output: ↓
    • Heart Rate: ↑
    • Central Venous Pressure: ↓
    • Pulmonary Capillary Wedge Pressure: ↓
    • SVR: ↓
    • Oxygen Saturation: ↓

Mnemonics

• Septic = Sat: Oxygen saturation is up in septic shock.
• Neurogenic = No HR Compensation: Heart rate is down in neurogenic shock due to lack of sympathetic tone.

Conclusion

• Understand the mechanisms and changes in each type of shock.
• Reason through up/down arrows rather than memorizing.
• Review key differences and compensatory mechanisms in each type of shock.