Shock Notes

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Prerequisite Knowledge

Seems unnecessary

Usage Tutorial

Concepts and Mechanisms

In simple terms:

  • Shock is essentially systemic ischemia. Blood supply requires maintenance of blood pressure, which depends on
    • Vascular resistance to blood, including vessel length, blood viscosity, vessel diameter,
    • Cardiac output = stroke volume × heart rate,
      • The less blood volume, the smaller the end-diastolic volume, and the smaller the stroke volume
      • If the heart has problems, stroke volume will also be reduced
  • When cardiac output decreases and blood pressure drops, catecholamines (such as adrenaline), antidiuretic hormone, and angiotensin 2 start releasing, causing vasoconstriction and increased heart rate to maintain perfusion
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Textbook definition: A group of clinical syndromes mainly characterized by metabolic abnormality and circulatory dysfunction caused by severe external or internal pathogenic factors (hypotension + sharp reduction in microcirculatory perfusion). Pathogenic factors include major hemorrhage, trauma, poisoning, burns, asphyxia, infection, allergy, and cardiac pump failure, etc.

Three Classifications

  • Hypovolemic shock: insufficient blood volume unable to meet body needs
    • Non-hemorrhagic, e.g., dehydration in the desert
    • Hemorrhagic (about 20% blood loss, approximately 1L is enough)
  • Cardiogenic shock (decreased cardiac output)
    • Direct injury, heart attack (e.g., acute myocardial infarction)
    • Obstructive shock, such as cardiac tamponade, physically limiting cardiac diastole, reducing stroke volume
  • Distributive shock (vasodilation, decreased peripheral resistance)
    • Anaphylactic shock
    • Neurogenic shock, nervous system damage unable to regulate blood pressure
    • Septic shock

Two Classifications

  • When perfusion decreases, blood flow slows and volume decreases, reducing heat delivery, causing tissue cooling, i.e., cold shock, such as hypovolemic shock, cardiogenic shock
  • In septic shock, vascular resistance decreases, blood races through rapidly, sometimes without releasing oxygen before it returns to the lungs, resulting in increased peripheral blood flow without cooling, possibly even warming up, i.e., warm shock

Treatment

Depends on the cause, prioritizing stabilizing blood pressure to ensure perfusion of vital organs (brain, heart)

  • Cardiac strengthening and vasoconstriction to raise blood pressure
  • Fluid replacement and antidiuretic therapy to restore blood volume
  • Oxygen therapy and airway protection to improve hypoxia
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