Internal Diseases · MU Sofia

Theory · 14. Shock and Circulatory Failure

Covers circulatory shock as acute failure to perfuse tissues, then walks through hypovolaemic, cardiogenic, obstructive and distributive shock in turn. Each type is set out with its causes, pathophysiology, signs and treatment, with distributive shock split into septic, anaphylactic and neurogenic forms. It closes with circulatory collapse, covering its general, specific and cardiac and peripheral forms and their causes.

Inside: 6 sections · 7 labelled pictures · 13 flashcards · 4 min

Topic 13 of 88 in the MU Sofia syllabus for Internal Diseases (Dental Medicine, Year 4). The free AceMed note covers it in 6 sections, about 521 words (4 min of reading), with 13 flashcards.

In this note

  1. Shock and Circulatory Failure
  2. Hypovolemic shock
  3. Cardiogenic Shock
  4. Obstructive Shock
  5. Distributive Shock
  6. Circulatory Collapse

Shock and Circulatory Failure

Definition

Circulatory shock (or simply, shock) = acute failure of the circulatory system to supply peripheral tissues and organs with adequate blood → leads to cellular hypoxia due to tissue hypoperfusion.

Types of Shock

Hypovolemic shock

  • Most common type
  • Cause: Insufficient circulating (intravascular) volume.
  • Non-haemorrhagic: Due to fluid loss (e.g., severe dehydration from vomiting, diarrhea, burns).
  • Haemorrhagic: Due to blood loss (e.g., trauma, GI bleed). Losing >20% blood (~1L) may induce shock.
  • Pathophysiology: ↓ End-diastolic volume → ↓ Stroke volume → ↓ Cardiac output (CO) → ↓ BP → activation of compensatory mechanisms (SNS → ↑ HR, vasoconstriction).
  • Symptoms:
  • Thirst (due to hypovolemia)
  • Tachycardia (compensatory for ↓ CO)
  • Cool, clammy skin (from vasoconstriction)
  • Hypotension
  • Oliguria (reduced renal perfusion)

Cardiogenic Shock

  • Cause: Failure of heart to pump effectively due to ventricular dysfunction.
  • Definition: ↓ CO, hypotension, tissue hypoxia despite adequate volume.
  • Common Causes:
  • Myocardial infarction (MI) – most common
  • Myocardial contusion
  • Sustained arrhythmias
  • End-stage CAD/cardiomyopathy
  • Pathophysiology:
  • MI → myocardial damage → ↓ contractility → ↓ SV and CO
  • SNS activation → vasoconstriction to maintain BP → ↑ afterload → worsens CO
  • Symptoms:
  • Hypotension (↓ CO)
  • Cool, clammy skin (VC)
  • Distended neck veins (↑ right atrial pressure)
  • Pulmonary oedema (from left heart failure)
  • Oliguria, cyanosis, fatigue (hypoperfusion and hypoxia)

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