Shock: Cardiovascular Collapse

Introduction

• Topic: Cardiovascular Shock (Not emotional shock)
• Definition: A clinical pathological condition where the cardiovascular system collapses, leading to widespread hypoxia and high mortality.
• Importance: Understanding this condition can help save lives.

Basics of Cardiovascular System

• Cardiac Output: 5 liters per minute in a healthy resting person.
• Blood Volume: Approximately 5 liters in a healthy person.
• Cardiovascular Capacity: Normally equal to blood volume (5 liters) ensuring the system is fully filled.
• Equal volume and capacity mean no disparity and effective circulatory function.

Causes of Shock

1. Disparity Between Volume and Capacity: Loss of blood volume reduces effective circulatory pressure.
2. Pump Failure: Due to myocardial infarction or other conditions, the heart cannot pump effectively even if volume and capacity match.
3. Increased Cardiovascular Capacity: Can be due to conditions like anaphylactic shock, neurogenic shock, septic shock, causing pathological blood distribution.

Types of Shock

1. Hypovolemic Shock

• Definition: Caused by inadequate blood volume.
• Examples: Hemorrhage, plasma loss in burns, dehydration from excessive sweating, severe diarrhea or vomiting, etc.

2. Cardiogenic Shock

• Definition: Caused by heart's inability to pump blood effectively.
• Examples: Severe arrhythmias, massive myocardial infarction, severe cardiomyopathies, valvular dysfunction, rupture of heart walls or septum.

3. Distributive Shock

• Definition: Caused by pathological dilation of blood vessels leading to peripheral pooling of blood.
• Examples:
  • Anaphylactic Shock: Severe allergic reaction causing massive release of histamines from mast cells.
  • Neurogenic Shock: Spinal cord injury or drug overdose leading to loss of sympathetic tone and vasodilation.
  • Septic Shock: Bacterial infections leading to release of endotoxins causing vascular dilation and inflammation.

4. Obstructive Shock

• Definition: Caused by physical obstruction of blood flow in the cardiovascular system.
• Examples: Cardiac tamponade, tension pneumothorax, massive pulmonary embolism, atrial myxoma.

Stages of Shock

1. Compensated (Non-Progressive) Stage

• Mechanisms:
  • Activation of sympathetic nervous system increasing heart rate, stroke volume, and vasoconstriction.
  • Renin-Angiotensin-Aldosterone System (RAAS) activated increasing blood volume and pressure.
  • Release of ADH (vasopressin) aiding in vasoconstriction and water retention.
  • Reverse Stress Relaxation reducing blood vessel capacity.
  • Fluid shift from interstitial to vascular compartments.
• Symptoms: Rapid pulse, cold extremities, anxiety.

2. Progressive Stage

• Mechanisms:
  • Worsening blood circulation leading to accumulation of lactic acid, myocardial depression.
  • Reduced venous return due to peripheral blood pooling.
  • Endothelial damage leading to more vasodilator release and permeability.
  • Risk of Dic and multiple organ failure.

3. Refractory (Irreversible) Stage

• Mechanisms:
  • Severe cellular and mitochondrial damage, release of enzymes from lysosomes.
  • Loss of ATP causing ion imbalances and cellular death.
• Outcome: Multiple organ failure leading to inevitable death.

Special Considerations in Septic Shock

• Pathophysiology: Release of endotoxins from bacteria leads to cytokine storm causing massive vasodilation, vascular leakage, and inflammation.
• Symptoms: Warm shock, possible fever or hypothermia, rapid bounding pulse.
• Diagnosis: Blood cultures, high levels of cytokines, monitoring for multi-organ failure.

Critical Factors and Management

• Causes: Hemorrhage, sepsis, myocardial infarction, allergies, obstructive conditions.
• Diagnosis: Recognizing symptoms, monitoring vital signs, and laboratory tests.
• Immediate Actions: Stabilize the patient, ensure effective blood volume, provide oxygen, and treat underlying causes.