Clinical Pathology · MU Sofia

19. Systemic hemodynamic disorders – peripheral tissue hypoperfusion (shock). DIC syndrome.

Covers shock as a systemic haemodynamic disorder, explaining how reduced blood pressure from lowered vascular resistance or cardiac output causes peripheral hypoperfusion. It sets out hypovolaemic, cardiogenic and distributive types with their skin-temperature signs, then the non-progressive, progressive and irreversible stages. It closes with DIC: its clot-driven mechanism, causes, laboratory picture, and the organs most affected.

Inside: 5 sections · 2 labelled pictures · 16 flashcards · 5 min

Topic 19 of 138 in the MU Sofia syllabus for Clinical Pathology (Medicine, Year 4). The free AceMed note covers it in 5 sections, about 816 words (5 min of reading), with 16 flashcards.

In this note

  1. Systemic hemodynamic disorders - peripheral tissue hypoperfusion (shock). DIC syndrome
  2. Peripheral tissue hypoperfusion (shock)
  3. Clinical stages of shock
  4. Pathology
  5. DIC syndrome

Systemic hemodynamic disorders - peripheral tissue hypoperfusion (shock). DIC syndrome

So when we talk about Ischemia, we’re talking about decreased blood flow to a particular tissue, which leads to tissue necrosis. Systemic hemodynamic disorder on the other hand are those conditions that affect the whole body, not simply a part of it (as per above). Here, we shall consider two types:

  • Peripheral tissue hypoperfusion (shock)
  • Disseminated intravascular coagulation (DIC) syndrome

Peripheral tissue hypoperfusion (shock)

Simply put, shock is a decreased level of blood perfusion through a tissue (that is to say, tissue doesn’t get enough blood).

This lack of blood perfusion generally a product of lack of blood pressure. Blood pressure has two primary determinants:

  • Vascular resistance to flow
  • Cardiac output
  • Heart Rate x Stroke volume
  • (Stroke volume = End diastolic vol - End systolic vol))

So, any of these elements that make up blood pressure can be affected to reduce the blood pressure and thereby trigger peripheral tissue hypoperfusion, we generally speaking categorise shock into three categories:

  • Hypovolemic shock (reduced blood volume)
  • Non-hemorrhagic (i.e. result of dehydration)
  • Hemorrhagic (from bleeding)

Here, reduced blood volume so reduced overall stroke volume, decreasing overall pressure. This means less blood forced through the tissue capillaries. Key indicator is a decrease in skin temperature, cold clammy to touch.

  • Cardiogenic shock

Here, we see something has happened to the heart to reduce cardiac output, this may be as a result of trauma, or Myocardial Infarction. In essence, reduced CO leads to reduced blood pressure and reduced perfusion. Also shows decrease in skin temperature.

  • Distributive shock (leakage of blood vessels and excessive vasodilation)
  • Anaphylactic shock
  • Neurogenic shock

Example: the commonest distributive shock is septic shock – bacterial products (e.g. endotoxin/LPS of gram-negative bacteria) trigger a cytokine storm (TNF, IL-1) that causes widespread vasodilation, capillary leak, endothelial activation and often DIC. It is a leading cause of death in intensive care units.

Here we see widespread vasodilation and vaso leakage in the peripheral vessels. This leads to decreased vascular resistance and thereby decreased blood pressure and decreased perfusion. Unlike the other two types of shock we are seeing an increase in blood flow, but it’s just not under pressure, so less perfusion. This increase bloodflow means skin temperature is warm to touch.

The general signs and symptoms of circulatory shock are:

  • Low blood pressure
  • Rapid heart rate (in an attempt to increase BP)

Continue reading free

The whole note, all 5 sections, is free with an AceMed account, with its 16 flashcards. Premium adds flashcard recall, highlights and Ask AI.

Start freeAlready a member? Open the note