Shock

Shock

David Ray Velez, MD

Table of Contents

Shock Definitions and Classification
Distributive Shock
Cardiogenic Shock
Hypovolemic Shock
Obstructive Shock

Shock Definition and Classification

Shock Definition

  • Definition: Inadequate Tissue Perfusion to Meet End-Organ Needs
    • Originates from the French Term “Choc”, Meaning a Violent Contact, Such as the Impact of a Jousting Lance
  • Cellular/Tissue Hypoxia from Reduced Oxygen Delivery, Increased Oxygen Consumption, or Inadequate Oxygen Utilization
  • Generally Caused by Circulatory Failure with Hypotension
    • Not Based Solely on Vital Signs
    • Can Present with Hypertension in Certain Cases

4 Classifications of Shock

  • Distributive Shock: Severe Peripheral Vasodilation (50% – Most Common Cause)
    • Septic Shock
    • Systemic Inflammatory Response Syndrome (SIRS)
    • Neurogenic Shock
    • Anaphylactic Shock
    • Endocrine Shock (Addisonian/Adrenal Crisis)
    • Drug/Toxin-Induced Shock
  • Cardiogenic Shock: Cardiac Etiology Causing Reduced Cardiac Output (14%)
  • Hypovolemic Shock: From Reduced Intravascular Volume (31%)
    • Hemorrhagic Shock
    • Non-Hemorrhagic Hypovolemic Shock
  • Obstructive Shock: Extra-Cardiac Etiology of Cardiac Pump Failure (1%)

Mortality

  • Distributive Shock: 20-50%
    • Septic Shock: 40-50%
    • Neurogenic Shock: 13-23%
    • Endocrine Shock (Addisonian/Adrenal Crisis): 6%
  • Cardiogenic Shock: 50-75% (Highest Risk)
  • Hypovolemic Shock: 20-37%

Hemodynamic Changes and Differentiation

 

Preload

(PCWP)

Contractility

(CO/CI)

Afterload

(SVR)

SvO2VC
Normal Levels8-12 mmHgCO: 4-8 L/min800-1,200 d/sec/cm-560-80% 
Distributive Shock↓↑1↓––
Septic↓↑↓↓/↑2↑
Neurogenic↓↓↓↓–
Cardiogenic Shock↑↑3↓↑↓–
Hypovolemic Shock↓↓↑↓↓
Obstructive Shock↓4↓↑↓–
  • 1: Distributive Shock Generally Causes Increased CO/CI Except in Neurogenic Shock Where it is Decreased
  • 2: Septic Shock Caused Decreased SvO2 Early Due to Increased Oxygen Consumption & Then Increased SvO2 Later Due to Decreased End-Oxygen Utilization (Not Impaired Perfusion)
  • 3: Cardiogenic Shock Due to Right Ventricular Failure Causes Decreased PCWP
  • 4: Obstructive Shock Due to Pericardial Tamponade Causes Paradoxically Increased PCWP Due to External Compression Despite Decreased Left-Sided Preload

Distributive Shock

Causes of Distributive Shock

  • Septic Shock
  • Neurogenic Shock
  • Anaphylactic Shock
  • Endocrine Shock (Addisonian/Adrenal Crisis)
  • Drug/Toxin-Induced Shock

Septic Shock

  • Definitions:
    • Sepsis: Life-Threatening Organ Dysfunction Caused by a Dysregulated Host Response to Infection
    • Septic Shock: Sepsis, Hypotension, and Lactate > 2 mmol/L
    • *Previous SIRS Definitions No Longer Used in the Definition of Sepsis
  • The Most Common Cause of Distributive Shock
  • *See Sepsis and Septic Shock

Systemic Inflammatory Response Syndrome (SIRS) Induced Shock

  • Definition: Shock Caused by a Profound Inflammatory Response
  • Can Be Infectious (Sepsis) or Noninfectious (Pancreatitis, Burns, etc.)

Neurogenic Shock

  • Definition: Shock Caused by a Loss of Sympathetic Tone from Severe TBI or Spinal Cord Injury
  • Seen in Spinal Injuries Above the T6 Level
  • *See Neurogenic Shock

Anaphylactic Shock

  • Definition: Shock from a Severe Allergic Reaction
  • Mediated by IgE with a Massive Histamine-Mediated Vasodilation
  • Most Common Cause:
    • Children: Foods
    • Adults: Insect Venom (Wasps & Bees)
  • *See Anaphylaxis

Endocrine Shock (Addisonian/Adrenal Crisis)

  • Definition: Shock Caused by Insufficient Adrenal Hormone Production
  • *See Adrenal Insufficiency

Drug/Toxin-Induced Shock

  • Definition: Shock Caused by Drugs or Toxins
  • Causes:
    • Drug Overdoses
    • Transfusion Reactions
    • Bites (Snakes, Spiders, and Insects)
    • Heavy-Metal Poisoning (Iron and Arsenic)
    • Cyanide

Cardiogenic Shock

Causes of Cardiogenic Shock

  • Cardiomyopathy
    • Myocardial Infarction (Most Common Cause)
    • Acute Decompensated Heart Failure (ADHF)
    • Blunt Cardiac Injury
    • Myocarditis
    • Advanced Septic Shock
    • Drug-Induced
  • Arrhythmia
  • Mechanical
    • Valve Pathology (Insufficiency, Rupture, or Stenosis)
    • Atrial Myxoma

Management

Hypovolemic Shock

Causes of Hypovolemic Shock

  • Hemorrhagic Shock
    • Trauma
    • GI Bleeding
    • Vascular Rupture (AAA)
    • Obstetric Hemorrhage
  • Non-Hemorrhagic Hypovolemic Shock
    • Dehydration
    • GI Loss (Vomiting, Diarrhea or External Drainage)
    • Skin Loss (Burns or Heat Stroke)
    • Renal Loss (Excessive Diuresis or Salt-Wasting Nephropathy)
    • Third-Space Losses (Bowel Obstruction, Operations, Crush Injury, Cirrhosis, etc.)

Hormones in Hypovolemia

  • Early Hormones:
    • Epinephrine and Norepinephrine (Adrenergic Response): Causes Vasoconstriction, Increased Contractility, and Increased Heart Rate
  • Late Hormones:
    • Renin (Kidney): RAAS Vasoconstriction and Water Resorption
    • ACTH (Pituitary): Increases Cortisol
    • ADH (Pituitary): Water Resorption

Fluid Responsiveness

Hemorrhagic Shock

Non-Hemorrhagic Hypovolemic Shock

  • First Vital Sign Changes:
    • Increased Diastolic Blood Pressure
    • Narrowed Pulse Pressure
  • Physical Exam Findings:
    • Dry Mucous Membranes
    • Decreased Skin Turgor
    • Low Jugular Venous Pressure
  • Treatment: IV Fluid Resuscitation
    • Crystalloids (LR) Preferred Over Colloids if Not Due to Hemorrhage

Obstructive Shock

Causes of Obstructive Shock

  • Pulmonary Vascular Obstruction: Right Heart Fails to Create Enough Pressure to Overcome Elevated Pulmonary Vascular Resistance
    • Pulmonary Embolism
    • Pulmonary Hypertension
    • Venous Air Embolism
    • High-PEEP Ventilation
  • Mechanical Obstruction: Decreased Venous Return to the Right Heart or Right Ventricular Filling
    • Tension Pneumothorax
    • Tension Hemothorax
    • Pericardial Tamponade
    • Abdominal Compartment Syndrome

Treatment

  • Primary Treatment: Correction of the Underlying Cause