Diagnosis of Shock

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What Causes Shock?

Diagnosis of Shock What Causes Shock?

Shock can be the result of numerous different pathophysiological processes that can be broadly accommodated within four somewhat artificial categories: hypovolaemic, distributive, obstructive and cardiogenic. [8] (Table 1)

Irrespective of the cause the inadequate delivery of oxygen to tissues results in a failure of aerobic metabolism leading to end organ dysfunction.

The situation becomes more confusing if examples of dysoxia are considered to be types of shock. Cyanide poisoning is a classic example wherein mitochondria are prevented from using oxygen. Such disease states are outside the remit of this module as the primary problem is not one of circulatory compromise.

Table 1: Categories of shock
Hypovolaemic (inadequate circulating volume secondary to
fluid loss)

Distributive

(inadequate perfusion secondary to
maldistribution)
  • Haemorrhagic (e.g. trauma, GI bleeding, obstetric haemorrhage, ruptured AAA)
  • Diarrhoea and vomiting
  • Diabetic ketoacidosis
  • Burns

  • Sepsis
  • Neurogenic shock
  • Anaphylactic

Obstructive

(inadequate cardiac output as a result of mechanical obstruction)

Cardiogenic

(inadequate cardiac output as a result of cardiac failure)

  • Pulmonary embolism
  • Tension pneumothorax
  • Cardiac tamponade
  • Acute IVC or SVC obstruction
  • Myocardial infarction
  • Myocardial contusion
  • Myocarditis
  • Late sepsis
  • Overdose (e.g. beta blockers)
  • Complete heart block

Learning bite

Shock describes a pathophysiological state with many different causes, NOT a specific diagnosis.

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